This is something I've been wondering about for awhile... Most people have told me that higher octane gas in my Corolla is a waste of money, and won't increase performance at all. So I decided to email Toyota and ask them... here's their response:
Thank you for contacting Toyota Motor Sales, U.S.A., Inc.
We appreciate the time you have taken to contact us.
For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating of 91 or higher is recommended.
Your email has been documented at our National Headquarters under file #200603290683. If we can be of further assistance, please feel free to contact us. Toyota Customer Experience
Octane doesn't affect energy content of gasoline, so it can't last longer. Unless your engine is designed for higher octane, in that case it would run less efficient if you didn't use it. Less efficiency = more gas used.
For the 98-02 Chevy Prizms (same as corolla) There is a Service Bulletin at dealers regarding this issue. I always used mid-grade in my car for the first 100000 miles, then I started having problems and losing power. Our engines don't have enough need for the high octane, so it doesn't all burn off, resulting in high carbon build up, to the point my valves were sticking and all sorts of power loss and stalling when cold. I used SeaFoam to clean out what I could, and I've used only 87 since and the problem mostly went away. I also spoke to our engineers here where I work, and they all said the same thing. Use the lowest octane you can use without causing pinging.
The manual for my 97 Corolla says to use "87 or higher". And with the response I got from Toyota, I'm pretty confident in using 91 octane. Shell V-Power seems to work really good for me. This doesn't seem to be true for all vehicles though... the manual for my mom's Jeep said not to use anything higher than 87.
Higher Octane is not required if you got your average 4AFE, 7AFE, 1ZZFE, or bigport 4AGE powered Corollas or Prizms. However if you own a Smallport 4AGE (90-91), 2ZZGE (XRS), or Supercharged 1ZZFE powered Corolla or Prizm.. you MUST stick to higher octane as much as possible as these motors are either High-Compression (4AGE, 2ZZGE) or Supercharged so you are running the risk of detonation and fucking up your motor if you run low octane.
I didn't believe it at first as when I got my 90 GTS the guy I got it from was running 87 Octane on it.. I was like.. are you retarded! you're supposed to run higher octane dude! I either run 89 or 91 or higher on this car.. the 89 GTS I put on whatever I find.
I found my 4af engine ran smoother with a higher octane. I need to have the carb looked at and cleaned and with the higher octane it didn't try to keep running after I shut it off :p. Even a 4af has a decent compression ratio, I think it's 9:1 or something around there... Will have to look it up in the service manual again
I've been bouncing back and forth for YEARS between 87 for several months and 89 for several months in the '96 Corolla DX. So far, the 87 gives better mileage overall to the tune of around 4 MPG regardless of driving conditions, season, or abusive acceleration, but the 89 makes the car run noticably smoother, especially idling.
FWIW, I believe the compression ratio on the 7AFE is 10.1:1...
yea the toyota 4 cyl seem to be fairly high compression... the higher octane's tend to burn quicker... because places like petrol canada but more detergents in them
and isn't 4mpg really bad?
yea the toyota 4 cyl seem to be fairly high compression... the higher octane's tend to burn quicker... because places like petrol canada but more detergents in them
and isn't 4mpg really bad?
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I either run 89 or 91 or higher on this car.. the 89 GTS I put on whatever I find. 
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