Doish13 Posted 21April, 2013 Report Share Posted 21April, 2013 Quick question - with my 78 model, should I be adding a fuel lead addictive with each tankful. Had a afternoon out with Caver and SteveF and this came up and would appreciate an educated answer. DB Link to comment Share on other sites More sharing options...
AC78 Posted 21April, 2013 Report Share Posted 21April, 2013 I put a dose of flash lube in my 79 every time I fill up. Some people have told me not to bother because apparently it has the hardened valves, but all the previous owners used it and the engine appears to be in excellent condition. Link to comment Share on other sites More sharing options...
cyberpunky Posted 21April, 2013 Report Share Posted 21April, 2013 You can get lead additive bottles(flash lube was what I used too) and top up each tank or you can install a drip feed system. I used the top up bottles in my old car and also used at least 95RON fuel, as I was told leaded fuel was a higher octane than base 91 unleaded My car ran great using this set up for years Link to comment Share on other sites More sharing options...
Doish13 Posted 21April, 2013 Author Report Share Posted 21April, 2013 Thank you gents - I only use Premium unleaded however this information I will note. Where do you pick this up from? Link to comment Share on other sites More sharing options...
tazzieman Posted 21April, 2013 Report Share Posted 21April, 2013 My 78 sc is designed for 91 octane (read the user manual , use what is recommended). Absolutely no advantage using premium 98 , except maybe some detergent action (not a problem if you use reputable servos and use your Porsche the way nature intended). No valve saver required, though I do use it in my '85 944 as no-one has been able to indicate if the Oz delivered ones had hardened seats or not. The cinderella 924 is the prissy one , needing 98. Link to comment Share on other sites More sharing options...
Doish13 Posted 21April, 2013 Author Report Share Posted 21April, 2013 That info will save me a fortune Link to comment Share on other sites More sharing options...
tazzieman Posted 21April, 2013 Report Share Posted 21April, 2013 Just avoid E10 at all costs I probably put a tank of 98 in every 5-6 refills. I probably don't need to. The car runs like a champ , always! Link to comment Share on other sites More sharing options...
Russ Posted 21April, 2013 Report Share Posted 21April, 2013 Yeah don't use ethanol blends hardened valve seats guides means no need for addatives, I always run 98 RON or better Link to comment Share on other sites More sharing options...
Harvs11 Posted 21April, 2013 Report Share Posted 21April, 2013 +1 on use whatever the manual for your car says. Higher octane than needed is just a waste of coin. Especially in a car without computerised engine management to control the ignition advance thus preventing detonation or knocking. Link to comment Share on other sites More sharing options...
SM911 Posted 21April, 2013 Report Share Posted 21April, 2013 Autohaus advised me that it was a waste of money, and it wasn't needed. I haven't used it for two years, and all's fine. If you don't need it, why bother? Link to comment Share on other sites More sharing options...
JustJames Posted 22April, 2013 Report Share Posted 22April, 2013 Two points to chuck into the mix:1 - 91 octane sounds very low. Are these American octanes? The merkins use a different measuring system for their octanes. While everything is understood to be bigger in Texas, merkin octane numbers are smaller for a given level of detonation resistance than numbers used in the civilised world.2 - Even though your car may not need the spendier higher octane fuel, it may well be that the spendier fuel works out cheaper because you may use less of it than the stuff with less caffeine content.James Link to comment Share on other sites More sharing options...
Uncle Posted 22April, 2013 Report Share Posted 22April, 2013 Eggsactly as James and Russ said. My 2 cents input. While you may not need to run 98 in an early car I bet my bottom dollar you will get more klm's per tank out of it if you do. Cheap fuel is the poster boy of false economy. The only time I would use "E" fuel is E85 on a car tuned for it... Link to comment Share on other sites More sharing options...
Doish13 Posted 22April, 2013 Author Report Share Posted 22April, 2013 So to add the additive or not? Link to comment Share on other sites More sharing options...
JustJames Posted 22April, 2013 Report Share Posted 22April, 2013 Minus the additive. Link to comment Share on other sites More sharing options...
tazzieman Posted 22April, 2013 Report Share Posted 22April, 2013 Two points to chuck into the mix: 1 - 91 octane sounds very low. Are these American octanes? The merkins use a different measuring system for their octanes. While everything is understood to be bigger in Texas, merkin octane numbers are smaller for a given level of detonation resistance than numbers used in the civilised world. As I recall , n the mid 70s there was concern about the availability of high RON fuel in the various world markets for Porsche. Regular ULP is still available in Tas (91 RON , in the USA this would be 86 RON). The owner's manual for my 78 engine states 91 (or greater) RON. It belies the owner to know what engine he/she has and some may have had an uprated comp ratio. As far as economy goes , I have never seen my oldskool 911 as being anything other than uneconomical as I drive it as nature intended. No sitting in queues for me! Link to comment Share on other sites More sharing options...
Uncle Posted 22April, 2013 Report Share Posted 22April, 2013 -AD Drive it however you like Taz. You will still get more ltr's/100 with 98 over 91. Link to comment Share on other sites More sharing options...
tazzieman Posted 22April, 2013 Report Share Posted 22April, 2013 Eggsactly as James and Russ said. While you may not need to run 98 in an early car I bet my bottom dollar you will get more klm's per tank out of it if you do. Cheap fuel is the poster boy of false economy. Can you quote independent scientific evidence to back up what I consider a pub myth , making oil companies even richer and motorists scareder? Wiki states "A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer" and " The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power." We are talking about older cars without knock sensors. Modern engines and forced induction/racing engines obviously are a totally different kettle. Link to comment Share on other sites More sharing options...
Uncle Posted 22April, 2013 Report Share Posted 22April, 2013 Really? http://en.wikipedia.org/wiki/Octane_rating Forget knock sensor and bang your head against the round thing with the 6 leads coming out of it next to the engine fan. If you ask me to disprove Chemtails next I am out of here. Link to comment Share on other sites More sharing options...
Russ Posted 22April, 2013 Report Share Posted 22April, 2013 lol doesn't a knock sensor just retard timing when it senses a knock? distributor timing is advanced without any sense of detonation and I for one can vouch on getting better mileage out of premium fuel in my 911 but YMMV Link to comment Share on other sites More sharing options...
Uncle Posted 22April, 2013 Report Share Posted 22April, 2013 P.S Wiki is not always a good place to get facts. Australia: "regular" unleaded fuel is 91 RON, "premium" unleaded with 95 RON is widely available, and 98 RON fuel is also reasonably common. Shell used to sell 100 RON petrol (5% ethanol content) from a small number of service stations, most of which are located in major cities (stopped in August 2008).[18] United Petroleum sells 100 RON unleaded fuel (10% ethanol content) at a small number of its service stations (originally only two, but it has now expanded to 67 outlets nationwide).[19][20] All fuel in Australia is unleaded. Link to comment Share on other sites More sharing options...
AC78 Posted 22April, 2013 Report Share Posted 22April, 2013 My owners manual says 91 at a minimum Link to comment Share on other sites More sharing options...
Harvs11 Posted 22April, 2013 Report Share Posted 22April, 2013 My simple understanding of the fuel ratings is this; a higher ron fuel can withstand higher compression before ignition takes place. Therefore requiring a different ignition advance setting to optimise the point of ignition within the combustion cycle. ie. a lower octane fuel in a high comp. engine will ignite (detonate) too early in the compression stroke and potentially damage the piston/cylinder etc. this is a cause of "engine knock". This is why manufacturers recommend a minimum ron fuel for their vehicles. However, a higher octane fuel, if used in a car tuned for lower octane fuel, will ignite at the correct timing thanks to the spark timing. Hence the importance of tuning your car to run on a particluar fuel. Or conversely, only using a fuel appropriate to your engines charactistics. I've got no clue about the density/economy claims. It does sound like a bit of marketing hooey to me though. Does any one on PFA actually know more about this? Link to comment Share on other sites More sharing options...
Doish13 Posted 22April, 2013 Author Report Share Posted 22April, 2013 You guys are doing my head in - if filling up with Kerosene next time. Did you say disprove Chem'trails'? My mate says it’s a true thing executed by the government and is the reason why i am losing my hair! Link to comment Share on other sites More sharing options...
JustJames Posted 22April, 2013 Report Share Posted 22April, 2013 About two years ago A Currant ToNight A Day ran a test where they drove supposedly identical cars at constant speed around a test track with x litres of fuel of varying flavours to see which was the most economical.....and the expensive fuel proved the most economical.Now, I couldn't tell you what cars they used so we don't know whether they used knock sensors to control timing, and we can question the scientific validity of the test method, but it did back up the notion that cheap fuel is more expensive than the good stuff. Link to comment Share on other sites More sharing options...
tazzieman Posted 22April, 2013 Report Share Posted 22April, 2013 lol doesn't a knock sensor just retard timing when it senses a knock? distributor timing is advanced without any sense of detonation and I for one can vouch on getting better mileage out of premium fuel in my 911 but YMMV Russ , that's a series of 1 to add to the anecdotes. Please find some science! "YMMV" doesn't cut it for me. My car feels like it goes better with low octane. Weird eh? Link to comment Share on other sites More sharing options...
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