Here in the VA are we have 87, 89, 93, 94 (I haven't seen 91).

After reading all the posts from people with chip upgrade. It seems their cars adapt and produce more HP with higher octane.

My question is, what about stock non-chipped cars, will running 93 octane be any different than running 91 ? 93 is everywhere, and Sunoco has 94. If stock cars get no gains, then I'll have to chip my car...

I've got a 1998 C280, I know I won't see the gains a S/C car gets, but where should I get the chip and what gains can I expect ? Maybe with 93/94 octane, I'll be surprised.

 

Most of the country is only able to get 91 max (short of racing fuel) and our cars run fine. I've tried 100 octane unleaded racing fuel from 76, drove around with it for a week to let the ECU adapt and before it was empty I put it on a dyno and didn't see a difference. If you go too low in octane eventually it will ping, the ecu will retard the timing and you will lose power and fuel economy. What that point is varies by outside temperature, humidity, how hard you drive your car, is your car tubo or super charged and any mods you have (pulleys, chip, exhaust, CAI). Since you have a I6 you can try 87 and 89 octane and see what happens, measure fuel mileage, see if you loose a little pep, get an OBD-2 scanner and see if the ECU is pulling back more timing than usual. Also in VA you have very high humidity, that acts like buffer in the combustion chamber to reduce pinging, also you live in a realitvely flat area so you don't have steep grades to climb that puts more stress on the motor like here on the left coast.

I know that when I had an Infiniti I30 that required premium I ran it on 87 all the time without any noticible difference. I know that 87 in my C230K would definately be not good, I've heard someone did a dyno and lost about 19hp with 87 vs. 91.

 

I do get mailage differences when i run 91 verses 87 on my MR2... only about an average of 10 miles difference...

 

I've got a 1996 J30 also (same as your engine ?), I'll test out the 87 octane and see if there is a difference.

What about CHIPed cars ? They show more HP during dyno tests.

Also, I've read (maybe here) with the right hardware/software one can set our cars to run on 93 octane. Which, in turn, produces more power.





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You get horse power from greater compression not higher octane. When you have higher compression you need higher octane to prevent pinging. People get confused by this and put high octane in an engine that was designed for 87. That is a total waist of money. The compression ration of that engine is only 8:1 so 87 octane is the best for it. A Mercedes or other performance / luxery car may have a 10.5:1 or better compression ratio so it needs 91 octane or better to perform. But the power doesn't come from the octane. The engine computer will make adjustments in timing to make up for the lower octane fuel you put in. If you don't run what it was designed for then you will lose power and get less miles per gallon. You won't create horse power by going to higher octane than what the engine was designed for.

 

e klasse is for the most part right, but the only area i disagree with him on is the compression. the compression doesnt make hp. more fuel and air burned in a given amount of time makes hp. for example if you take an engine with 10:1 ratio and dont give it enough fuel then its numbers will be low. now if you take the same engine at 8:1 and have it receiving the proper amount of fuel/air it will probably make more hp then the other engine with a higher compression. yes giving a car designed for 87 octane, 91 octane is a waste of money and there is no performance difference.

 

On my forced induction coupe it does feel to respond and maintain power longer through the power band with Sunoco 94.

I run the car almost emply then put 5 bucks worth in for Autocrossing. Again, this is only seat of my pants and could be just my imagination.

 

The point I was making was that if you have 2 cars with the same size engine but one has 10:1 compression and the other has 8:1. With the correct timing and no extra options, the one with 10:1 compression will have more HP. The one with 10:1 compression will be running a higher octane fuel but the HP gain is not coming from the higher octane.

Yes there are other factors to generating more HP but octane is not one of them.