87 works just fine for my '99

 

In the Blazer I am running 89 right now. The reason is most places around here has 89 priced 2 cent more then 87 for some reason. You can really get away with whatever you want with these motors, maybe up the octane if towing, but other wise you should be fine.

The Z gets nothing but 93. The car is tuned perfect for 93 and going lower to even 91 (if it were available here) will cause severe pinging during the summer months. She has seen 101 octane race fuel once. Man was that a nice run!

The wifes RSX is mixed. She usually runs 87, if I am going to be driving it a good deal I run 93. The car falls on it's face with 87 when compared to 93. Only the Type S models require 91+, but damn I could swear that they tuned her motor for it as well. It's amazing.

 

what are the benefits of running 87 or 91??

 

87 in the Blazer and 93 in the street car

 

87:
benefits: cheap
91/92/93:
Benefits: Runs better, stronger, doesn't spark knock, increased horsepower and torque, help keeps fuel system cleaner.

I run 93 once a month and when I'm pullingto keep the fuel system conditioned. The rest of the time, I use 87 simply because its cheaper.

 

Not entirely true Euro...

The octane rating of a fuel is a measure of the fuel's resistance to pre-detonation. As such, a higher octane fuel is also more difficult to ignite. To fully utilize a higher octane fuel, an engine must be designed to use it, whether that is by increasing compression ratio or forced induction or just increasing the spark advance (which won't entirely take full advantage of the fuel).

It is possible that deposits will form over time and create pre-detonation causing hot spots. If you find that a vehicle runs better on 89 when the manufacturer recommends 87, it may be caused by deposits in the combustion chamber. If an upper engine cleaning doesn't cure this problem, then it will be better for your engine to run 89 octane fuel. The reason behind this is that when pre-detonation is detected by the knock sensors, the PCM will retard the timing (knock retard), reducing the potential for power in an effort to save the engine.

A tune may also increase the octane requirements. However, without a tune that makes full use (through higher spark advance) of premium (91+ octane) fuel, you really won't be getting everything that you could possibly be getting from the fuel. Even at that, spark advance can only increase the power so much.

I would say that everyone should test what their vehicle likes best. Keep track of the miles travelled and the gallons used over 3 tanks or more of fuel for each octane you choose. Also keep track of the price of the fuel you are using. At the end, calculate out the average $/mile for each and use the one that performs the best in that regard.

About E10 fuel (10% ethanol blend). In NY, I believe that every pump is an E10 pump. I couldn't be happier. When the change happened in my local town, my vehicles ran better on the E10 than on the prior 100% gasoline fuel. With E10, you can reduce the frequency of fuel system treatments/cleaners as ethanol will clean the deposits left behind by gasoline as well as disolve water due to condensation in the fuel tank or other means of introduction.

 

Wow I didn't know ethanol was that great. Can't imagine I'll see it in the high altitude Rockies anytime soon though (after all, we still have 85 for pete's sakes[sm=boosign.gif]). First time I saw it was in Nebraska somewhere heading back from Minneapolis to Colarado and the 89 ethanol was cheaper than the regular 87. I used the 87 just cuz I didn't know what ethanol did to a vehicle. Now I know.

 

Just to be clear, our engines cannot handle E85 (85% ethanol). But concentrations up to 15% can be tolerated. Some people have experienced poor mileage when switching to an ethanol blend, but stick with it. As the ethanol cleans out deposits, the engine is bound to run a bit worse. In my experience, every vehicle has a different rate of cleaning. For some, it may not get worse, for others, it may be over a few tanks. You may have to replace the fuel filter after the first few tank fulls.