Mineral or Synthetic

[Paul Carrera]

 

Mineral or Synthetic Without wishing to start another oil debate I would like to know what everyone is using. I am using synthetic but looking at previous posts most seem to favour mineral so I am wondering if I should switch and why. I have a 86 911 that is 100 percent dry as I have just done all seals and tubes etc

[Peter M]

Early synthetics had a well deserved reputation for causing leaks but I think those days are gone now that elastomer compatibility is tested in the ACEA and the later API test sequences and the oil companies have had to even out the shrink/swell caused by their various products. 

(I can recall changing from conventional to an early Penrite PAO in the nineties in a Nissan Skyline that started to leak within days!  Tightening the cam cover bolts fixed it but was surprised at the on/off nature of the change.)

However if we ever think our air cooled engines are going to be permanently oil tight, I think we are fooling ourselves.  Is there a production engine that has more gasket faces and seals than a Mezger?  I just think its inevitable no matter the oil used.

I haven't come across anything that suggests there is a correlation between viscosity and corrosion/wear in a stored engine.  In my own experience from pulling down engines that they are always well lubricated even if they have been sitting a long long time.

As for synthetic, semi or conventional comparisons I don't think you can do that on any sensible basis as there is no consistent definition of the various types.  I think it's better to forget the chemistry and just compare engine oil on the basis of HTHS and then use the various ACEA/API and manufacturer certifications.

 

Or just use GTX and forget all this oil mumbo jumbo......  

 

  

Paul,

Post from another recent thread on using Castrol GTX 10w-40 of all things in a car that's still going strong after 400,000 miles.

To answer your question I have one on conventional and one on synthetic and both are leak free.  The conventional gets changed over to synthetic next month not because I necessarily want a synthetic oil, it just meets the manufacturer approvals I'm interested in such as MB 229.5 and I got it on special at Repco!

My advice is it doesn't matter, it's not a critical choice in ensuring the longevity of the engine and just use what you think is best.

Edited 18August, 2015 by Peter M

[ANF]

A well respected Porsche mechanic once told me that cars designed and built to use mineral oils should always do so and vice versa.

From his experience when synthetics get hot (more so on really hot days) the oil pressure would drop (sometimes to almost 0) in cars designed to run on mineral that were now running synthetic - he simply changed out to mineral and the oil pressure came back.....

[Pauly]

It was designed to run in mineral oil. so that's what you put in it. 

[tazzieman]

 

Mineral or Synthetic Without wishing to start another oil debate I would like to know what everyone is using.

Everyone? You should start a poll! But the question has been adequately answered.

[Coastr]

I don't understand how an oil that meets manufacturer specifications and is rated to a particular viscosity can somehow be 'thinner' because it is synthetic.  Unless the viscosity ratings are incorrect somehow - but then why would they be?   Are we talking mineral vs synthetic or 'thick' vs 'thin' here? 

When I was a kid my local milk company changed hands or at least changed packaging.   I was excited by the new packaging and, upon tasting, declared to me dear mum that the 'new milk was creamier tasting'.  Of course this is complete rubbish and much fun was made.

I often think that with synthetics vs minerals, we're all just 5 year old kids looking at a new milk carton and declaring the taste creamier without thinking it through.

[Stew F]

Mine has semi synthetic Magnatec Professional 15W40, just to put a cat amongst the birds.  Car has been running with that for around 6 years with PO, then when I had it serviced at the same place that's what they used.  I contacted the Castrol rep and he suggested Magnatech Diesel.  I'm totally confused!  Was thinking of changing to Penrite.

[tazzieman]

Mine has semi synthetic Magnatec Professional 15W40, just to put a cat amongst the birds.  Car has been running with that for around 6 years with PO, then when I had it serviced at the same place that's what they used.  I contacted the Castrol rep and he suggested Magnatech Diesel.  I'm totally confused!  Was thinking of changing to Penrite.

A funny thing happens to people who start using good old Aussie Penrite. They stop lying awake at night thinking about oil. That, as Clarkson would say , is a Very Good Thing.

[Peter M]

A well respected Porsche mechanic once told me that cars designed and built to use mineral oils should always do so and vice versa.

From his experience when synthetics get hot (more so on really hot days) the oil pressure would drop (sometimes to almost 0) in cars designed to run on mineral that were now running synthetic - he simply changed out to mineral and the oil pressure came back.....

 

It was designed to run in mineral oil. so that's what you put in it.

Pauly and Adam,

I am pleased that your mechanics are not your doctors as they would be still using leeches on you!

 

Don't get me wrong, a good mineral oil does the job just as well as a good synthetic but to say that old engines should only use mineral oil has no rational basis.  Oil pressure is solely related to actual viscosity the engine sees, not chemical composition.  

 

Mine has semi synthetic Magnatec Professional 15W40, just to put a cat amongst the birds.  Car has been running with that for around 6 years with PO, then when I had it serviced at the same place that's what they used.  I contacted the Castrol rep and he suggested Magnatech Diesel.  I'm totally confused!  Was thinking of changing to Penrite.

Stew,

Magnatech Diesel 15W-40 would work fine as it is a quality dual rated oil for both petrol and light duty diesel engines.  Castrol states it:

Meets and exceeds API SN/CF, ACEA A3/B3, A3/B4 requirements

Edited 19August, 2015 by Peter M

[LeeM]

Mineral. Penrite. That is all

[clutch-monkey]

in the end..

 

it doesn't matter

 

doesn't make any goddamn difference.

Edited 19August, 2015 by clutch-monkey

[Norm]

 

Pauly and Adam,

I am pleased that your mechanics are not your doctors as they would be still using leeches on you!

 

Don't get me wrong, a good mineral oil does the job just as well as a good synthetic but to say that old engines should only use mineral oil has no rational basis.  Oil pressure is solely related to actual viscosity the engine sees, not chemical composition.  

 

Stew,

Magnatech Diesel 15W-40 would work fine as it is a quality dual rated oil for both petrol and light duty diesel engines.  Castrol states it:

Meets and exceeds API SN/CF, ACEA A3/B3, A3/B4 requirements

Is that perhaps because newer or certain types of engines have different or specific metallurgical composition, which are designed to work with mineral or synthetic oil?  

If if it made no difference why do you manufactures use synthetic at all?

[firstone]

It leaves less deposits.

[Peter M]

 If if it made no difference why do you manufactures use synthetic at all?

For us drivers of old cars that don't care about fuel economy, operate in a very mild climate, do only a few thousand km a year and change the oil annually, no practical difference.

However, once you start running ultra low viscosities for fuel economy reasons (0w-20 and  soon to be lower), extended oil change intervals and topped with some specialised manufacturer requirements, synthetics forge ahead.

Engines aren't designed on the basis oil mineral or synthetic but viscosity (HTHS viscosity in particular as that's a better model of what the bearings for example actually "see") and expectations of where the various bits are operating on the Stribeck curve and this then largely dictates the antiwear compounds needed.

 

Sorry Norm, my knowledge of lubrication is now exhausted!  

Edited 19August, 2015 by Peter M
Forgot to add we don't operate in the Yukon!

[TINGY]

For us drivers of old cars that don't care about fuel economy, do only a few thousand km a year and change the oil annually, no practical difference.

However, once you start running ultra low viscosities for fuel economy reasons (0w-20 and  soon to be lower), extended oil change intervals and topped with some specialised manufacturer requirements, synthetics forge ahead.

Engines aren't designed on the basis oil mineral or synthetic but viscosity (HTHS viscosity in particular as that's a better model of what the bearings for example actually "see") and expectations of where the various bits are operating on the Stribeck curve and this then largely dictates the antiwear compounds needed.

 

Sorry Norm, my knowledge of lubrication is now exhausted!  

Huh! Seriously, you could probably run chainsaw bar oil through your engine and it would do the same job!

[tazzieman]

Huh! Seriously, you could probably run chainsaw bar oil through your engine and it would do the same job!

You'll stihl be discussing this in 12 months time.

[Coastr]

My understanding is that manufacturers now recommend synthetics, usually at 0W-20 or lower because the engines can be made to finer tolerances and synthetics also allow for longer oil change intervals, which is key in keeping costs down during warranty, esp if servicing is included.  Perhaps you can't make a mineral oil that performs the same in terms of longevity for that requirement.  I know most of the synthetics meet the BMW LL1 long life requirement, not sure if many mineral oils do.  I've always fed my BMW Mobil 1 and the inside of the engine looks like new (even though BMW recommend Castrol!)

If you remember the old Mobil 1 ads they used to show deposits in a turbo oil lines - with coked up lines from the mineral oil and clean lines from Mobil 1.   That's what they first were trying to sell on - clean vs dirty.  

For the record I file most 'experienced mechanics' opinions on oils under 'old wives tales' - not because I'm smarter, but because few would actually be oil experts and even the number of vehicles going through their shop is just not a statistically valid sample to draw experience from.

[Peter M]

My understanding is that manufacturers now recommend synthetics, usually at 0W-20 or lower because the engines can be made to finer tolerances......

For the record I file most 'experienced mechanics' opinions on oils under 'old wives tales' - not because I'm smarter, but because few would actually be oil experts and even the number of vehicles going through their shop is just not a statistically valid sample to draw experience from.

Coastr,

These lower viscosities are being used on modern engines to reduce friction as there is a strong correlation between HTHS and fuel economy. I understand it is in the order of a couple of percent so it's any easy win for all manufacturers and excites the trucking industry too.

Here is one of many studies on this matter with some nice clear graphs towards the end to illustrate:

http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&ved=0CB8QFjAAahUKEwjtitTWoLbHAhUn26YKHWPvBlA&url=http%3A%2F%2Fpriuschat.com%2Fattachments%2Ffuel-efficient-motor-oil-technical-article-pdf.11772%2F&ei=PgvVVe3zKKe2mwXj3puABQ&usg=AFQjCNHO0ufAYvJvA9slPlLP3fDCKRgZ9Q

 

 

I couldn't have said that second paragraph better and that's my conclusion too. 

Edited 20August, 2015 by Peter M

[Pauly]

I know a few guys with 944 turbos (designed to use 20w50) who rebuild their engines and ran synthetic post build. It wore out the bearings quicker than when running mineral oil.. Same problem with a few guys. all using OEM bearings. 

Engines with flat tappets and with a lot of friction really need the minerals.  

[tazzieman]

Engines with flat tappets and with a lot of friction really need the minerals.  

But

 10W-60 Porsche Classic Motor Oil is an ultra high performance oil. This fully synthetic oil is suitable for the air-cooled flat six engines of the 911 models from the 3.0 liter engine and up

Porsche says so 

[Peter M]

LOL, I'm worn out, not because of a lack of viscosity or effective modern anti wear compounds, but beliefs based on shaky, statistically invalid observations.

In all my posts on this topic in this and other threads, I have tried to separate fact from fiction as best I could and to ultimately allay unfounded fears for both myself and fellow PFA'ers.   I can't stand the fear mongering that commonly goes on in oil threads based on the poor root cause analysis and unfortunately, in some cases vested interests.

 

Edited 20August, 2015 by Peter M

[clutch-monkey]

LOL, I'm worn out,

 

this wouldn't have happened if you'd used a mineral oil! my mechanic said so

Edited 20August, 2015 by clutch-monkey

[tazzieman]

Peter I think with the paleo diet and a bosu ball you can regain your inner feistiness 

Porsche embodies endurance and tolerance of adverse environments.

Olive or canola?

 

[Peter M]

Olive or canola?

Valid alternatives. Each have their place and I'm very comfortable with that.

Edited 20August, 2015 by Peter M

[Coastr]

You know if we really want to get to the truth of the matter we need to find a trucking fleet manager who uses oil analysis to keep an eye on the rolling assets.

I think it wouldn't be an exaggeration to say that one single rig would cover more KMs in a year than the entire fleet of PFA cars combined does in 5.  Multiple that 1 rig x 100, all with the same engine and fuel and you start to understand statistical significance, and why a bunch of us with different cars with varying histories and many versions of oil can't really come up with a conclusive answer.