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Join Date: Sep 2010
Location: Alberta, Canada
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I'd like to point out a few things in the 87 vs 91 (93 w/e) debate.
In a way there no real benefit, or something the average user would notice.
But heres the catch.
Running premium in an older low compression motor wouldn't do anything. Keep the engine a bit cleaner yes but other then that nothing.
Then again is keeping your engine cleaner really nothing? But having to run a premium blend for cleaning reason can be avoided by running a better brand of gas. To the average user you wont get it but you do get what you pay for and some of the bigger companies are running a better blend. So personally I might run the costco brand gas in my 86 corolla if I had to but not my Golf. Reasons being quality control, car is tuned a certain way and the difference between shell premium and lets say a 7-11 premium is noticeable in knock and power... ANYWAYS.
Regarding newer cars with the multiple O2 sensors and knock sensors they can detect fuel qualities and hundreds of running perimeters. This is where it gets interesting.
When a car is marked to run 87 octane it can and will run just fine and happy. The ecu gives fuel and pulls timing with knock and adjusts how much fuel is delivered with the AFR that the O2 sensors sense. The thing is, is that although your engine may run happy with 87 , 87 gas does not burn as nice. (Like the good ol saying : You get what you pay for)
Anyways 91 is a much more refined and controlled fuel, thus burning better. Your car's O2 sensors see the AFR change and can reduce fuel levels to reflect this. Thus you get less fuel and more timing advance with no knock = better performance. and when your casually driving you get better mileage.
So running 91 DOES make a difference. It has been Dyno proved and specifically the article I read was on a VW. They only gained 8-15 hp but this was across the band and the engine responded better. (probably due to the extra timing advance the ECU gave due to the lack of knock)
Anyways Im rambling but I believe that 91 is worth it as two of my cars only take 30-40 bucks from empty. so the extra few bucks in premium usually gets me farther.
Best "Bang" for your buck I might say lol.