Rec'd Octane for 911SC?
08-05-2002, 05:09 PM
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Rec'd Octane for 911SC?
What type of gas (87, 89, 93, 94+ octane) runs best in 911SC? Mainly interested in street use with light track use.
Any suggestions?
Any suggestions?
08-05-2002, 05:35 PM
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I use only 93 Chevron in my 1986 911. I have always been told by Porsche/Bosch/BMW certified mechanics to ONLY use 93 in a high compression 911 engine, and many specified Chevron ONLY. Using anything less would cause premature detonation which causes higher operating tempertures.
I wouldn't use anything higher such as airplane or race fuel because these can cause the rubber seals and such to dry out....these are usually dry running fuels. I would only run these in a track only car.
93 is fine for the racey daily driver,
--Brian
I wouldn't use anything higher such as airplane or race fuel because these can cause the rubber seals and such to dry out....these are usually dry running fuels. I would only run these in a track only car.
93 is fine for the racey daily driver,
--Brian
08-05-2002, 05:53 PM
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For what it's worth, the Owner's Manual for my '80 SC specifies 87 octane. Then again, it also says to only change the oil once a year or every 15,000 miles. I hope others will chime in on this but, for starters I would say:
87 Probably okay for day-to-day street use if
your car is completely ummodified and you
know that the timing is correct. I'll
confess that I use it from time to time.
89 A cheap security blanket for unmodified cars.
My car probably doesn't need it but it makes
me feel better. My usual choice - and
probably a waste of money (but not much).
93 I'm inclined to top up (at least 1/2 tank) of
this for track days. Contrary to much of the
advertising, there's no performance benefit
(I suspect there may even be a barely
measurable decrease in horsepower) compared to the "correct" octane rating for your
engine. Given the high RPM and engine
temperatures at DEs, however, it's
detonation insurance.
94+ Unless you've changed to high compression
pistons, etc, it's money down the rathole.
Looking forward to the other responses.
87 Probably okay for day-to-day street use if
your car is completely ummodified and you
know that the timing is correct. I'll
confess that I use it from time to time.
89 A cheap security blanket for unmodified cars.
My car probably doesn't need it but it makes
me feel better. My usual choice - and
probably a waste of money (but not much).
93 I'm inclined to top up (at least 1/2 tank) of
this for track days. Contrary to much of the
advertising, there's no performance benefit
(I suspect there may even be a barely
measurable decrease in horsepower) compared to the "correct" octane rating for your
engine. Given the high RPM and engine
temperatures at DEs, however, it's
detonation insurance.
94+ Unless you've changed to high compression
pistons, etc, it's money down the rathole.
Looking forward to the other responses.
08-05-2002, 06:27 PM
#4
RL Technical Advisor
[quote]Originally posted by Jeff Randall:
<strong>What type of gas (87, 89, 93, 94+ octane) runs best in 911SC? Mainly interested in street use with light track use.
Any suggestions?</strong><hr></blockquote>
Hi Jeff:
Good question with a not-so-simple answer.
Over time, all engines build carbon inside each cylinder on the piston crowns & on the combustion chamber surfaces. This buildup slowly raises the effective compression ratio and raises the octane requirements of these engines. Fuel additives like Techron and LubroMoly do not remove these deposits and one must be cognizant of this phenomenon and use the best gasoline available in your area.
For track use, where you can run the engine harder & longer than you can on the street, cylinder heads temps are higher and I always recommend one to mix some unleaded race gas for those occasions. Its good insurance as you'll never hear the type of detonation that does the most damage to rings and pistons.
<strong>What type of gas (87, 89, 93, 94+ octane) runs best in 911SC? Mainly interested in street use with light track use.
Any suggestions?</strong><hr></blockquote>
Hi Jeff:
Good question with a not-so-simple answer.
Over time, all engines build carbon inside each cylinder on the piston crowns & on the combustion chamber surfaces. This buildup slowly raises the effective compression ratio and raises the octane requirements of these engines. Fuel additives like Techron and LubroMoly do not remove these deposits and one must be cognizant of this phenomenon and use the best gasoline available in your area.
For track use, where you can run the engine harder & longer than you can on the street, cylinder heads temps are higher and I always recommend one to mix some unleaded race gas for those occasions. Its good insurance as you'll never hear the type of detonation that does the most damage to rings and pistons.
