85 octane

No issues with 85 octane in our 3/4 ton Chevy gasser since we live and primarily do most of our RVing at high elevations. I never seen much difference in performance using the lowest grade available, but do notice a minor bump in mpg on the rare occasions that we have opted for supreme grade.

At a certain point in elevation (and I do not know what it is) they sell lower octane fuel they say it has to do with the elevation and that it is not required or better said it is not needed for the benefit of the higher octane. I have bought vehicles here and while the owners manual will state use 87 or whatever and have had dealers tell me just use 85 or whatever the next lowest grade is compared to what is in the manual. Here you typically see 85,87,89 octane instead of the 87,89,91 that I see at lower elevations. I've been in Colorado for several decades and it has been this way for as long as I have been here. If I recall the benefit of higher octane is to help prevent pre detonation but apparently the lower density of the air (ie oxygen) at elevation provides the same benefit so they don't go to the extra cost of production for the higher octane ratings.
I think, maybe

bobkatmsu wrote:
While traveling out west this summer I noticed most of the gas stations offering 85 octane and 87 octane as their mid grade. Has anyone tried this in their gasser? I wasn't going to try it especially in the mountains.

In the mountains, at high altitudes, is where you should use it. I use it every time I am out West and are going to be driving at higher altitudes.
All of the newer engines are controlled by computers that will adjust things as necessary so that your engine will perform fine with 85 octane fuel. You most always find 85 gasoline at stations that are a mile or so above sea level. Use it and save a few pennies. Your engine won't mind a bit.