91 vs 93 octane
 

The manual asks for 93 octane, but in my area I can't seem to find higher than 91. Will the ECU automatically compensate for this, and what is the implication? I've seen in some other posts that the ECU is programmed for a specific octane...

RE: 91 vs 93 octane
 

What year car are we talking about?

Lee

RE: 91 vs 93 octane
 

It's a 2001...

RE: 91 vs 93 octane
 

I would ask the dealer, but all modern cars now can take a little lower octane. The newer cars like yours have anti knock sensors and they will adjust timing along withother alogorithems so the car does nor knock or ping.

Ask or call a dealer but for me i would use 91 if it does not ping or knock you are good to go. If you prefer you can go to a autostore and buy octane enhancers. I have never used them by my drag freinds say they work well on cars with high compression.

Alot of people use high test fuels in cars that cannot use it. High compression engine use it for antiknock protection and better performance. new vehilces that the maunfacturer suggests 87 octane will actually give less gas milage and no better perforamnce if 93 is used. This is different from olden days caused by modern electronics.

Lee

RE: 91 vs 93 octane
 

Cool, thanks Lee!

RE: 91 vs 93 octane
 

91 is fine in your car. We can't get anything above 92 in Kansas either. The ecu will adapt, especially with the anti-knock.

RE: 91 vs 93 octane
 

I'll bet the original poster is located at a high altitude. I could be wrong, but I thought the Octane rating was affected by the altitude, such that 91 rated gasoline out here in Colorado (5000 feet and higher) was actually physically and chemically identical to 93 rated gasoline at sea level.. It would make sense that it's 92 in Kansas - half way
between the two extremes.

So the original poster is running the recommended gas for his vehicle, it's just rated different at altitude..

- RA

RE: 91 vs 93 octane
 

RA,

You are right in the impact of altitude on engines and detonation. Airplanes use 100 oct fuel because they need the extra protection against premature detonation that can cause engine damage over time and a landing where you had not planned. Airplanes have to "lean" out the mixture as they go higher to maintain the proper stoichiometric mixture to obtain maxium engine output. For the atlitudes cars go incluidng Leadville at 9200 feet the cars electronics can handle this.On old cars or carburated Harley Davidsons the driver can tell the difference.

Cars today take this into account with the design electronics in the car.Thus is especially truefor fuel injected cars.

Lee

RE: 91 vs 93 octane
 

Actually I'm in San Jose, CA. Pretty close to sea level. I guess CA mandates the lower octane premium gasfor better emissions. But I'm not sure...

RE: 91 vs 93 octane
 

9200? Nah, try closer to 10,400. Our place in Breckenridge is at 9600, and we routinley go over 11 k (Eisenhower Tunnel, on I70
to the ski places in CO, is just over 11k), and sometimes close to 12k (Loveland Pass, if you don't want to go through the tunnel)

Even new cars lose a lot of power at that altitude. My wife's '06 Bimmer does OK on the approach to the tunnel, but
you still gotta downshift and keep the revs up a bit higher. And we pass a *lot* of cars chugging along at 40 mph or so...
High altitude is where a turbo makes a *huge* difference - my wife's previous car was a turbo Saab, and that
sucker would pull hard all the way up to the top of the pass. Ramming all that air into the pistons helps a lot
when the air itself is thinner...

Can't afford a turbo Porsche ;( I'm in the process of buying a normally aspirated 911 c4.. it'll be interesting to
see how well it handle's the altitude. I suspect it'll be like my wifes BMW - fine as long as you keep the revs up a bit.

- RA