911 Engine oil preference

[webrest]

A lot of work went in to that, Excellent! 

 

Thank you.

 

+1

[DHE11]

Couldn't help but being sucked in to reading this thread, and I remember reading them all when I first bought my air cooled Porsche,especially on the US forums. You were asking for thoughts and experience... I found a lot of thoughts and not much commentary on experience when I read them all so here goes, and hope it helps...

My thoughts:

After doing all the research, I drained the semi synthetic oil the PO was using and moved to a pure high quality mineral oil. (It was out of Brad Penn and Swepco that seemed to include all the essential elements for the older air cooled cars). I ended up going with Swepco 306 because 1/ it was easier to find in NSW at the time, and 2/ because their 201 gearbox oil also seemed to be highly recommended for older Porsche gearboxes, so buying cartons with 5 x 306 with 1x 201 included was convenient and economical for shipping.

My experience:

After running 306 for over a year, I did end up with Mobil 1 in my engine for a short time after the car went in for a unplanned shop service which needed the oil system disrupted. I couldn't get my own oil to the car in time so they filled it with Mobil 1. It was fine, and I ran it for a while on the street and did one or two track days, no problems. I did however notice based on the garage floor evidence that it leaked more than the mineral oil did in my engine. Aside from start up, hard to say if it burned more, as your always topping up these cars, especially during and after track days. When I did the next oil service I changed the Synthetic out and went back to the Swepco. I didn't experienced any issues moving from original semi to mineral to full synthetic back to mineral oil, but did fully drain the engine, tank, lines etc and change filter each time.

I have been running the same (old) engine for about 2 1/2 years now on Swepco 306, in a mix of city, highway (back and forth to Wakefield Park and interstate trips), plus lots of track days. The car has several lap records and won it's class and came second outright in club championships, meaning it has does its fair share of hard track work and regularly sees high RPM (as its been custom tuned and had it rev limit further increased) with no problems to date. I also use their 201 gearbox oil and find that to be good in the 915 gearbox. Again, because of track duty I change it often, at least twice a year.

Whether I do it myself, or supply my own oils at major service time, changing engine and gearbox oil regularly it the best advice, no matter which oil you choose, it's cheap insurance!

Because of the frequency and amount I and others were ordering, the local rep (Dan - contact: ordertheoil@gmail.com) has started to hold more Swepco stock in NSW which saves time and freight cost of ordering from interstate in small quantities (normally comes out of Melbourne)

If you choose a mineral oil, contact Dan, he gives good deals on Swepco 306 and 201 (comes in gallon containers) to Porsche NSW club members, or just tell him it's for a Porsche and he'll look after you on price (normally it's the other way round and you get gouged as soon as you mention the P word)

If you choose to go with synthetic, when I needed to buy top up quantities of Mobil 1, I found it was cheapest to buy in 1 quart bottles off eBay.

Happy motoring with whatever you decide.

[Peter M]

How could I overlook Swepco!

Darien,

Thanks for posting and I'll update that spread sheet accordingly.

EDIT: Bahhhh!

No mention of ZDDP content in the product data sheet! Why do some companies make it hard for the fanatics!

http://www.swepcolube.com/products/swepco-306-supreme-formula-engine-oil

Further contact details for NSW distributor:

[clutch-monkey]

Don't really want to start another huge oil debate, just coming up for an oil change and thought i would see what the consensus was out there?

 

My car had an engine rebuild 6 years and around 12K prior to my purchase, in that time and according to the receipts suppled it had 4 oils changes 2 with Fuch Fully synthetic and 1 with Mobil 1 (Porsche dealer) and one just stated as 10lt of fully synthetic oil? 

 

When I got the car i researched the which oil question to the point of brain ache! I ended up talking to one of the local independent Porsche specialists and they said they used (and importantly had been using for some time) they recommend Castrol Magnatec 10-40 Semi - Synthetic so that was what ended up going for.

 

I don't drive like Miss Daisy and I don't cane the backside off the car either, I would like to do an occational track day in the future but not on the cards at the moment. I intend to change the oil and filter annually or 10000km whichever comes 1st. The car got a major service in July 2013 and by the time that comes around this year I estimate I will have done around 6500 - 7500km.

 

Please share your experiences and thoughts.

my car has run for ten years plus on the current engine (no idea if/when it was rebuilt prior).

it's happy enough on the penrite oils, usually 10w40 or similar.

still running strong, no leaks, no smoke.

it even lived on castrol magnatec fine - oil was being swapped out every month or so, so all the long life advantages the marketing hyped up meant nothing.

[Caledonian]

Thank you all for your contributions/thoughts/experiences and spreadsheets and while I know this topic has already been discussed/debated for ever and a day, there is some good stuff here.

 

While i've still not fully decided which oil to use, i have now narrowed it down to 2 (now 3 with Swepco ) but i defiantly know what i won't be using.

 

Oil be going now

[Peter M]

And there's more!

While I added in the Swepco options, it was the Amsoil 20w-50's that impressed me.

Oil be off then too, it's been interesting!

EDIT: Removed attachment as I've learnt a bit more since I originally created the spread sheet and there are easier ways of selecting suitable oils besides looking a constituents! See my later post on selecting oils in 3 easy steps.

[Peter M]

OK, I admit I can't help myself!

A recent post about an oil change made me think about my previous posts on oil selection for post ’84 air cooled 911’s and what I have learnt in the meantime. I think the use of my old 911’s are similar to many others where they are not used daily, only travel a few thousand km a year, I change the oil yearly because that’s what the market expects to see in the maintenance log book (and the fact that the cost of doing used oil analysis (UOA), while no doubt providing interesting some facts is not worth the expense) and generally the trips are unfortunately less than 50km at a time.

When I first made these posts I was mainly concerned with ZDDP content, being readily available and having an appropriate viscosity. After a bit of research I decided to try a highly regarded mixed fleet oil, 15W-40 Caltex Delo 400 in my ’85 because it ticked all the boxes. My experience has been good, the hot oil pressure is plenty high, runs great and I definitely won’t be going back to the 20W-50 it ran before, let alone consider using anything thicker.

More reading has made me realise:

Oils Have Come a Long Way – The driver’s manual recommendation for this car are now almost 30 years old and there has been a lot of engine oil development in this time. When you consider the first commercial multigrade 20W-50 developed by Duckham’s to largely address the demands of the combined sump and gearbox of a BMC Mini in the early 60’s, we need to read the recommendations of driver’s manual with the knowledge of the limitations of the oils available at that time, such as the expectation of significant viscosity shearing of multigrades and be open to exploiting the technological advances that have come since.

ZDDP – More isn’t better and in fact it’s the effectiveness of the overall additive package that matters. Also the restrictions on the use of Phosphorus, the “P” in ZDDP, in modern engines has forced oil manufactures to look at different additives to protect engines from wear. ZDDP has been popular because it is cheap and effective and not because it is magical. Also let’s realise that when Mezger designed this engine, no commercial oils had ZDDP as an additive and its eventual common use in our cars came about from drivers adopting newer technologies as it became available.

Hot Oil Pressure – If you achieve around 10psi or about 2/3 of a Bar pressure per 1000rpm when the engine is at operating temperature, your hot viscosity is fine. Running any thicker oil will just increase engine temperatures, cause more wear from a cold start as the engine takes longer to reach the right oil operating viscosity or by causing the relief valves in the oil line or worst, the oil filter to open unnecessarily.

All Cold oils are Too Thick to Provide Best Protection – There is also a commonly referenced statistic that something like 90% of engine wear occurs on cold start up, so even if this is only half accurate, cold oil characteristics are important to us. Further, irrespective of whether the oil is a 0W-50 or a 20W-50, the cold viscosity is still 8 to 15 times thicker than the ideal hot operating viscosity. So this is why we all need to drive gently until the engine and the oil in particular achieves operating temperature.

So what is the Right Hot Oil Viscosity? – Porsche recommend a minimum HTHS viscosity of not less than 3.5mPa.s. Will going to a higher HTHS provide my street car better protection? Nope! The easy way to guarantee this requirement is met is to simply select an oil that complies with the ACEA classifications A3/B3 or A3/B4. Another easy way is to only use oil that has the “Porsche A40” approval marked on the container.

Misinformation Abounds! – Self professed “experts” who perpetuate myths litter every forum. However if you keep looking there are a few oil gurus around worth listening to.

Porsche A40 Approval – Porsche issues an approved list of engine oils for all Porsche vehicles manufactured after 1984 used worldwide. I find this list interesting for two reasons: that there are only two oils on the list that have xW – 50 viscosity classifications, the rest are 0W-40 or 5W-40 and that as a group of enthusiasts we all broadly ignore their recommendations! (I think this list is probably the best example of my first point of how oils have come a long way. Otherwise they would still be endorsing the use of mono grades shown in the table on page 92 of my 1985 driver’s manual!)

Maintain an Effective Air Filter – as the dirt just finds its way into your oil where it accelerates wear. Sometimes we need a reminder of how important these are to engine longevity.

Choose a Good Oil and Stick With It - Best results come from a long term relationship. It’s also the only way to get good UOA information if you want to take this to the next level of real world analysis.

So what am I going to use for my next oil change?

Haven’t decided yet, but I reckon it’s going to be a name brand 0W-40 or 5W-40 with at least 1100ppm of Zinc. They exist, are readily available and provide the best cold start and hot wear protection so why not exploit modern oil technology in our old cars just like we have done previously?

[Coastr]

Mobil 1 retail pricing has gotten to the point where I gave up on it.  I think the 1 stands for '1st on the price list'.

[AC78]

On a similar note, dropped in to local Porsche dealer to enquire about Porsche Classic motor oil.  Guy behind the counter narrows his eyes - asks me if I want it because I like the can or because I need it for an oil change (I only wanted it for the can, naturally).

 

Guy says all the cans in Australia are damaged, as Porsche doesn't care about boxing them up nicely before shipping them down under.  I suggested that most of the oil sales will be to people like me who only want the cans for their man cave, and that my comment should be pushed back to head office.

 

Guy suggested I come back in a few months when new batches arrive, and he's had a bunch of people in already saying the same thing.

 

Anyway, that's all I had to say, carry on

[TINGY]

Gee's Pete, a bit more light reading!

[au-yt]

I havnt seen this article mentioned, Great cure for insomnia but has huge detailed infomation..

http://speedtalk.com/forum/viewtopic.php?t=30483

[09ELF]

and the debate continues..

 

This chart is great.. HPR15 or 10 tenth prem5  would be next for me.

I like the fact it is readily available

 

http://www.penriteoil.com.au/tech_pdfs/1192%20February%202014%20-%20Automotive%20Engine%20Oil%20Summary.pdf

[HowardMoon]

Synthetic oils are vastly superior to dinosaur based on every technical measure...

 

 

Oh really? I hear this a lot but I'm not convinced. "Synthetic" covers a lot of different types of oil. No doubt most of it is very good, but as someone who has encountered corrosion from esters and PAOs that turn into vegemite I'm not so universally enthusiastic. It's biggest advantage as far as I'm concerned is its low temperature performance. It is often cited as having superior high temperature characteristics as well but this isn't always true - some minerals are more stable than some synthetics at high temps. And for very high temps castor is still the benchmark. For all their faults at least mineral oils are usually predictable.

 

But anyway, I think we may be attacking this from the wrong end. Instead of asking "What oil should I use? And what do you use?" perhaps the right question would be "Who here has lost a lobe recently? And what oil were you running when it happened?"

 

Notice I didn't mention ring, bore or journal and bearing wear. In reality, you simply aren't going to see abnormal bearing wear if you have a consistent supply of unaerated oil, even if it's only Kmart stuff. Likewise, ring and bore wear isn't normally a lubrication issue unless temps are extremely high. The only place that the unit pressure is high enough that the lubricant is a factor is in the valvetrain with most engines. And I'm not sure it's worth all the attention it's getting with regard to Porsche engines.

 

The whole ZDDP/lost lobe thing came to a head quite a few years ago now when many US racers suddenly started to wipe out cams and lifters for no apparent reason. Cam grinders were flooded with warranty claims and the blame was placed in various areas. It took a while for the main reason (the change in oil composition) to become apparent as there were other changes (different lifter and cam core metallurgies) happening at the same time. But anyhow, things settled down once people took care to avoid some of the new style oils.

 

But I think it's important to keep things in perspective: a lot of those engines make extreme demands on oil. Take a racing BBC for example; it wasn't uncommon for these to run well over 400lbs over the nose. Multiply this by a 1.8 rocker ratio and drive it with a lifter of only .842" diameter and you can see the loading at the cam/lifter interface is exceptionally high. Add the inertia loads from belting a heavy 55-60mm valve open at 8-9000rpms (plus a pushrod) and it's easy to see why keeping the cam alive was such a challenge. Of course these days nearly everyone runs rollers so it isn't such a big deal, but where the rules dictate flat tappets it's still an issue. Another good example is Nascar, where pushrods and flat tappets are the rule and engines run 9000rpms+ for 500 miles.

 

The Porsche engine by contrast is very lightly loaded. There are no pushrods, the valves (and therefore springs) are much lighter yet the contact patch probably at least as big. The lift is lower and there are no pushrod cups to smoke either. Likewise the bearing loads are much smaller - a 1200hp BBC pushes that torque through only five main bearing that aren't much bigger than the Porsches. So what I'm getting at is the oil choice with these engines probably isn't such a big deal. I'm not saying you should be running KMart 15/40, but realistically you probably could. I realize everyone is just trying to get as long a life as possible from their engines, but if the oil is good enough to keep the surfaces separated then extra capacity isn't really going to gain much. But if it makes you feel good to use a super-duper synthetic go for it. The best thing you can do for a long life is to limit the number of cold starts as much as possible - and incidentally most of the ring and bore wear from cold starts is actually caused by corrosion from byproducts of incomplete combustion, not wear as such.  I'm not a triboligist (someone who studies trilobites) but I'm pretty sure oil choice for these engines isn't worth losing sleep over.

 

Anyhow, I'll leave you good folk alone now - I only stumbled on this place accidentally (researching the Kibbert effect coincidentally) and never meant to stay.

[J.J.]

Brad Penn (green oil) is great for 911's requiring ZDDP

[tomo]

Hi, if you read the link provided by au-yt : http://speedtalk.com...pic.php?t=30483 it shows through his testing that the oils with the high Zink content tend to performe not as well as those with lower zink content bloody oil,  the less said about it the better.    

[HowardMoon]

Hi, if you read the link provided by au-yt : http://speedtalk.com...pic.php?t=30483 it shows through his testing that the oils with the high Zink content tend to performe not as well as those with lower zink content bloody oil,  the less said about it the better.    

 

The guy that wrote that is a bit of a crackpot; his methodology is suspect and his results don't align with empirical, real-world, in-the-actual-engine-results. He's been banned from a few forums for irritating people with his ongoing oil crusade.

[Peter M]

 

Oh really? I hear this a lot but I'm not convinced. "Synthetic" covers a lot of different types of oil. No doubt most of it is very good, but as someone who has encountered corrosion from esters and PAOs that turn into vegemite I'm not so universally enthusiastic. It's biggest advantage as far as I'm concerned is its low temperature performance. It is often cited as having superior high temperature characteristics as well but this isn't always true - some minerals are more stable than some synthetics at high temps. And for very high temps castor is still the benchmark. For all their faults at least mineral oils are usually predictable.

 

But anyway, I think we may be attacking this from the wrong end. Instead of asking "What oil should I use? And what do you use?" perhaps the right question would be "Who here has lost a lobe recently? And what oil were you running when it happened?"

 

Notice I didn't mention ring, bore or journal and bearing wear. In reality, you simply aren't going to see abnormal bearing wear if you have a consistent supply of unaerated oil, even if it's only Kmart stuff. Likewise, ring and bore wear isn't normally a lubrication issue unless temps are extremely high. The only place that the unit pressure is high enough that the lubricant is a factor is in the valvetrain with most engines. And I'm not sure it's worth all the attention it's getting with regard to Porsche engines.

 

The whole ZDDP/lost lobe thing came to a head quite a few years ago now when many US racers suddenly started to wipe out cams and lifters for no apparent reason. Cam grinders were flooded with warranty claims and the blame was placed in various areas. It took a while for the main reason (the change in oil composition) to become apparent as there were other changes (different lifter and cam core metallurgies) happening at the same time. But anyhow, things settled down once people took care to avoid some of the new style oils.

 

But I think it's important to keep things in perspective: a lot of those engines make extreme demands on oil. Take a racing BBC for example; it wasn't uncommon for these to run well over 400lbs over the nose. Multiply this by a 1.8 rocker ratio and drive it with a lifter of only .842" diameter and you can see the loading at the cam/lifter interface is exceptionally high. Add the inertia loads from belting a heavy 55-60mm valve open at 8-9000rpms (plus a pushrod) and it's easy to see why keeping the cam alive was such a challenge. Of course these days nearly everyone runs rollers so it isn't such a big deal, but where the rules dictate flat tappets it's still an issue. Another good example is Nascar, where pushrods and flat tappets are the rule and engines run 9000rpms+ for 500 miles.

 

The Porsche engine by contrast is very lightly loaded. There are no pushrods, the valves (and therefore springs) are much lighter yet the contact patch probably at least as big. The lift is lower and there are no pushrod cups to smoke either. Likewise the bearing loads are much smaller - a 1200hp BBC pushes that torque through only five main bearing that aren't much bigger than the Porsches. So what I'm getting at is the oil choice with these engines probably isn't such a big deal. I'm not saying you should be running KMart 15/40, but realistically you probably could. I realize everyone is just trying to get as long a life as possible from their engines, but if the oil is good enough to keep the surfaces separated then extra capacity isn't really going to gain much. But if it makes you feel good to use a super-duper synthetic go for it. The best thing you can do for a long life is to limit the number of cold starts as much as possible - and incidentally most of the ring and bore wear from cold starts is actually caused by corrosion from byproducts of incomplete combustion, not wear as such.  I'm not a triboligist (someone who studies trilobites) but I'm pretty sure oil choice for these engines isn't worth losing sleep over.

 

Anyhow, I'll leave you good folk alone now - I only stumbled on this place accidentally (researching the Kibbert effect coincidentally) and never meant to stay.

Howard,

I hope "HowardMoon" isn't your real name and you are actually a beautiful woman as I'm sure I've got a crush on you now!

As for lobe wear in air cooled Porsches, it is not unknown for them to suffer pitting and for the follower pads to wear. Hence there is broad interest in antiwear compounds like ZDDP.

Warm regards

Peter

[HowardMoon]

 

Howard,

I hope "HowardMoon" isn't your real name and you are actually a beautiful woman as I'm sure I've got a crush on you now!

As for lobe wear in air cooled Porsches, it is not unknown for them to suffer pitting and for the follower pads to wear. Hence there is broad interest in antiwear compounds like ZDDP.

Warm regards

Peter

 

How could you tell I wasn't male?? All I want to do is build smallblock Fords but for some reason the guys won't stay focused...

 

I've got no idea about the pad wear, but pitting is usually a sign of fatigue of the hard surface layer and not related to lubrication. I know the Pinto guys have had similar problems so it may pay to look into that. If I was looking for oil advice I'd probably listen to the cam grinders over anyone else; they are the ones with the warranty on the line. Quite a few of them seem to like Brad Penn, and all (that I know of) will void warranty if you don't use a zinc oil and their moly additive for break-in.

 

Regards,

    Christina.

 

[tazzieman]

 

I've got no idea about the pad wear, but pitting is usually a sign of fatigue of the hard surface layer and not related to lubrication. 

 

Regards,

    Christina.

 

Are you perchance post menopausal Christina?

You realise that real men need real zinc for virility & fertility?

Stuff like "Brad Penn" sounds manly enough to keep one's Penrite

[Peter M]

Mobil 1 retail pricing has gotten to the point where I gave up on it.  I think the 1 stands for '1st on the price list'.

I agree. Even though M1 0w-40 is THE premium oil I can't justify $98.99 a jug particularly when it will be barely stressed before being replaced in 12 months. (And why is the 5w-50 20 bucks cheaper?)

So for the A40 approved oils, Fuch TITAN Supersyn LONGLIFE 5W-40 seems the most affordable at $55 for 5 litres or 50 bucks if you ask nicely at Bursons. http://www.fuchs.com.au/ProductDetail.aspx?product_id=39550&product_name=TITAN Supersyn LONGLIFE SAE 5W-40&product_code=4153&product_category=&product_category_id=41

However today I notice that Repco have Shell Helix Ultra 5W-40 on special until Thursday for $30 for 5 litres (55% off !) Ticks all the boxes for me so I bought 15 litres.

Other affordable alternatives particularly if you have zddp "hangups" and not interested in the A40 or A3/B4 accreditations are the well regarded mixed fleet CI-4 oils like Delvac MX, Delo 400 and Rimula R4X. Admittedly limited to 15w-40 viscosities but easily available at about 40 bucks a jug at most servos or around $125 for a 20 litre drum from a depot.

Penrite do some well priced options too but their "Extra 10" and "Full Zinc" advertising irritates me to the point that I just find them hard to take seriously. Irrational I know but we are talking about engine oils after all........

[clutch-monkey]

I agree. Even though M1 0w-40 is THE premium oil I can't justify $98.99 a jug particularly when it will be barely stressed before being replaced in 12 months.

this is the key here imo. most of us change oil regularly enough that there's barely any advantage in going for the premium stuff.

when i was racing more regularly i used cheap castrol magnatec. it's fine.

[StevepGT3]

Aside from the zddp issue,here is a Quote from a very well respected air cooled engine builder

 

http://rennsportsystems.com/

 

Originally Posted by chaoscreature 

Exactly. That's why I use the lighter 5w-40. If I were to take my car to the track on a 95 degree day I would probably change to a heavier oil.

FWIW,....5w oil is way too damned thin for these air-cooled engines unless you are in arctic conditions. Main bearing thrust wear is accelerated using that stuff. (Works OK in the water-boilers since their tolerances are quite different)

I would recommend a 15w-40 for you.

__________________
Steve Weiner
Rennsport Systems
Portland Oregon
503.244.0990

For Performance Parts and Upgrades, Machine Shop Services, & Technical Information, visit us on the Internet at:
http://www.rennsportsystems.com
E-mail: porsche@rennsportsystems.com

Follow us on Facebook, too.

 

 

[Peter M]

Steve,
I agree Mr Weiner is a successful engine builder but I suggest we can all learn new ways of doing things.

Unfortunately the link to his website doesn't take me to anywhere in particular so I can't see the theme of that thread to comment.

However I would suggest the same reasons that Steve suggests using 15w-40 over say a straight SAE40 viscosity oil is the same reasons we should consider exploiting oil developments in the last 20 years and to use a 5w-40 or 10w-40 viscosity. All these oils have the same hot viscosities of around 13 to 14 cst but the important cold start up - where the majority of wear occurs in practice - is "only" around 7 times too thick for best protection rather than 15 times too thick!

I agree the early high VI oils would shear down to provide less than ideal hot viscosities but that issue has been solved I would suggest.

Don't think I'm taking this change of thinking easy as I've a 35 year habit of using 20w-50 in cars that I'm now questioning! Going to 15w-40 on my last change was big step and 5w-40 on the next will be another step to better exploiting modern technology.


 

FWIW,....5w oil is way too damned thin for these air-cooled engines unless you are in arctic conditions. Main bearing thrust wear is accelerated using that stuff. (Works OK in the water-boilers since their tolerances are quite different)

I would recommend a 15w-40 for you.

I find this an odd claim. I'm assuming he is comparing a 5w-40 to a 15w-40. If so:

• Both offer the same hot temperature viscosity at around 14cSt at 100C or just greater than 3.5 cSt in the High Temperature High Shear test at 150C.
• The 5w -40 offers slightly better start up protection because it would be around 85 cSt at 40C verses around 120 cSt for the 15w-40. This important difference gets much greater at the temperatures that our cold engines are at start up.  However it is important to note that a 5w-40 cold is still much much thicker than a 15w-40 hot so I can't see how a 5w is "too damn thin".  Remember that multigrade oils were developed originally to reduce the cold to hot viscosity variation.  Modern high VI oils are simply another step closer to engine oil utopia.
• I'm not sure how a slightly quicker pumping oil (cold) can be blamed for increased thrust bearing wear. (going back to the point above about viscosity and assuming he is talking about this as his description of the bearing is a little unconventional.)   I would suggest there are other causes with greater correlation.
• I'd also suggest that main bearing clearances (he says "tolerances" but he actually means clearances.  Tolerance is a measure of acceptable variation to a specified clearance)  haven't changed much over the last 70 years so to say there is "quite a difference" has to be questioned.

I think a better source of factual information are the fleet owners and the industry oil test regimes as this information is gained from a larger sample size and a more controlled "test" environment rather than the 99.99% of anecdotal postings on the internet that have only have at best, circumstantial root cause analysis.

 

Sure I accept that there will always be a "thicker is better" view and variations of this and there is no doubt the thicker oils have serviced our needs in the past, all I'm suggesting is that technology is improving each day so let's exploit it.

 

Cheers

Peter.

 

PS: For simplicity, all comments above relate to street driven cars with engines in good condition.

[911oclock]

Hey Peter,

So what's the lay of the land on high K air cooled engines? Do we stay with the old practice of using heavier oil and if so would a 20w-50 then be more appropriate?

[Peter M]

Hey Peter,

So what's the lay of the land on high K air cooled engines? Do we stay with the old practice of using heavier oil and if so would a 20w-50 then be more appropriate?

I've changed my view on this too and suspect the need to go to a heavier viscosity for a high kilometre engine is often overestimated. Also what is the definition of a "worn" or "high kilometre" engine? Very subjective so I would continue to use the following approach:

Provided I am achieving a minimum of 10psi or about 2/3 Bar of hot oil pressure per 1000rpm, I would stick with using Xw-40 grade.

(Actually the API viscosity gradings are so broad that it is more useful compare oils on their HTHS viscosities. We need a minimum of 3.5 cSt which is what we get when we buy a oil with ACEA classification A3/B3 or A3/B4. This is Porsche's recommendation for our post '84 cars as well.)

If I couldn't achieve reasonable oil pressure with the above Xw-40 oil, only then would I would then seek out a heavier oil as measured by the HTHS viscosities. If this is the case I would be exploring the newer 5w-50, 10w-50 and the 15w-50 API classifications first before considering a 20w-50 because of the same cold start reasons discussed earlier which are equally valid for new engines and old.

Again be wary of relying solely on the API classification alone as it is only with looking at the product data sheets that you can actually get some sense with viscosities. For example you would think Fuchs's TITAN Supersyn SAE 10W-60 would have a lower cold viscosity than Mobil 1 V-Twin 20w-50? The reality is that they are identical! (170cSt vs 174 cSt respectively at 40C.)