Since i bought my GS I fill up my car roughly once a week or so at about $40 a tank. I wasn't used to such a high amount since I used to own an MR2 and an Acura CL, but anyways my girlfriend suggested I use 76 gasoline cause she said "it gets better gas mileage". So I did an experiment with 3 different gasses and my results might surprise people. Each time I waited till the gas light came on and I proceeded to fill it up to a full tank each time. I drove roughly the same route (work and here and just a few miles around town, nothing drastic) everyday about 40-50 miles a day for a month. Mostly freeway too. Oh, I always drive w/ AC. The results:

Shell: 297mi
Chevron: 310mi
76: 345

Yup! 345 big difference, eh? Another buddy of mine also suggested I use 76 he said for some reason thier gas burns a lil bit more slowly. If anyone has an opinion to this I'd like to hear about it. Thanks and again this was jes an experiment, don't yell at me with ur scientific conclusions...hehe

 

I have only had chevryon 91 in my car since day one, so I really don't have experience with other gasolines. I just like the techron. hehe

I averaged 21 mpg on my last fill up even with intake, exhaust, and heavy rims. Freeway and city driving is 50/50. Multiplying 21 mpg and the 21.1 gallon tank would mean I could get 443.1 miles on a full tank.

Weird thing is that when my needle is below the 1/4 area, I still have 6-7 gallons left. Incase your wonderin how I did the math, topped off the car then drove till it was 1/4 left and topped off again. Whichever amount of gas it took to fill up was I subtracted from 21.1. Then the mileage driven divided by the amount of gas purchased.
-Bryan

 

from personal experience, i haven't noticed a significant difference between the big brand gas (Chevron, 76, Shell) but i DID notice a significant drop in mpg when i was cheap and tried ARCO.

 

The 5M-GE motor in the Cressida liked the 76 gas and it eeked out a hair more mileage in that instance. The plugs were also were reasonably clean but I did notice after a spell that they did begin to foul with a yellowish crud.

With the LS, I haven't noticed a difference and have used ARCO 99% of the time. Plugs are clean and best highway miles has been 28.7 MPG, with air on that drops to 26.X. Around town...I don't want to know...it is something like 13-14 MPG.

My Celica being quite unsophisticated will burn almost anything happily with the exception of Exxon.