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Hello all how you all doing. I have a question about the difference between regular 85octane and mid grade 88 octane in my 1996 toyota tercel 1.5L 16V DOHC 5 SM trans it says to use no lower than 87 octane fuel. That is at sea level correct. I live in Utah and the elevation is about 4400ft above sea level, I think that's why our regular unleaded is 85 not 86 or 87.
Do you know if I were to run 88 octane fuel would I get better or worse fuel econmy, and would it run any smoother or cleaner?

Any help on this topic would be wonderful

Thanks, Scott T. Morris

Hi Scott, You have a good question here, and even though I don't have the answer, here's a link to a good recent discussion on the topic. At least one hypermiler had his best MPG was on a tank of 85 octane. http://www.cleanmpg.com/forums/showthread.php?t=12968

I'm inclined to believe that, as long as, your engine does not "ping" the cheaper 85 octane would be my choice, but my local stations only offer 87, 89, and 91. Anyone else out there want to chime in? :D

91 will give the best results on the 1994 5speed Saturn-SL when using all the tricks. 94 octane is available here ... even better

Hi Tercel, good question. I used 85 octane while driving through the Rockies. My older vehicle was built for 87 octane, but I don't recall the owner's manual saying to never go below this.

It would be hard to do, because the only place I've seen 85 octane was above 4,000 ft. I figured it couldn't really hurt, as long as it did not cause pinging under load (and it didn't). In fact, I got the best mileage ever on that vehicle with that gas!

I know it wouldn't work down on the flats where I live, but I was amazed that the best mileage I got was climbing up and down mountain passes. That doesn't compute in my feeble brain.

So, go for it. The best advice is to use the cheapest gas that does not cause your engine to ping (except under very hard load - not something that most hypermilers experience).

Steeper climbs provide best opportunity for lengthy use of the best torque speeds (best potential-energy gain per ounce of fuel) before FASing again for long periods up toward/across level over the peak including accelerating/descending down again.