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.

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.

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

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.

Hi,I'm reasoning that, as has been said, at the higher elevations, the atmospheric pressure is less, thus less air is being drawn into the cylinders on a normally aspirated engine. Since there is less fuel/air charge in the cylinder, pre-ignition becomes less of an issue (similar to having a lower compression ratio), so a lower octane (octane is added to help limit pre-ignition) fuel can be used. That is why normally aspirated engines produce less power at higher altitudes. Slap on a turbo-charger or super-charger and this effect is minimized greatly. I'm sure there are more technical explanations, but I believe that is it in laymans terms. ~Rick

As stated, when at elevation, 85 octane is just fine.BUT (read that a large BUT) this means only when driving at high elevation.So, if you will be in mountain driving at lower elevation (say, when you are returning from high elevation to lower but still in some "upgrades to pull", do not fill with the lower octane.We face this when we travel from home(elevation 22') to Angel Fire, NM (elevation 8,400'). No problem with 85 octane while in the Angel Fire area, but we wait until lower elevation to fill up when returning to Texas. The other option would be to fill with mid-grade when at high elevation stations.

85 octane | Good Sam Community

Chum_lee
Explorer
Sep 28, 2017
Passin Thru wrote:
You can burn 100LL aviation fuel. We use it in a Sequoia. Has 132,000 hard miles all with a trailer.

Yes, you can use 100LL and your modern computer controlled engine and it will work just fine. The problem will be that after a little while your catalytic converter (if equipped) won't. If you are getting 100LL avgas for free that would be a good option, but, if you have to pay retail price for it and your vehicle is subject to emissions inspections, probably not.

100LL avgas is way too expensive! Currently, in the Southwest US, 100LL avgas runs about $5.39/gal.

Chum lee
Y-Guy
Moderator
Sep 28, 2017
Our trip to Utah a few years ago I filled up with 85, OMG never again. Elevation or not our RV felt like a slug . Never again.
Passin_Thru
Explorer
Sep 28, 2017
You can burn 100LL aviation fuel. We use it in a Sequoia. Has 132,000 hard miles all with a trailer.
wolfe10
Explorer
Sep 28, 2017
Coffee Grinder wrote:
I have a 2017 F 53 V - 10 and just got back from Jackson Hole and Colorado going over Wolf Creek with E 85 and no problems at all. There may have had issues with older engines

E85 or 85 octane???
ArchHoagland
Explorer
Sep 28, 2017
I run 85 in my 2004 8.1 gas engine all over the west and never had a problem.
Coffee_Grinder
Explorer
Sep 28, 2017
I have a 2017 F 53 V - 10 and just got back from Jackson Hole and Colorado going over Wolf Creek with E 85 and no problems at all. There may have had issues with older engines
wilanddij
Explorer
Sep 27, 2017
When you drive I-15 thru Utah, you will notice regular is 87 octane in St. George (elevation about 2K') and it is 85 octane in SLC (elevation about 4.2K'). Every vehicle I have owned since 1980 has not had a problem with the fuel.
wa8yxm
Explorer III
Sep 26, 2017
That is common at higher altitudes.. I do understand why, but My motor home did not care for it

(Lower atmospheric pressure means the compression in the cylinder is lower so you can get by with lower octane.. IN short, Thin Air).

But as I said my motor home did not care for it, ran bad till I re-upped with 87
Lwiddis
Explorer II
Sep 26, 2017
Some of my fellow posters may be experts on gasoline, octane and modern GM engines but none of you will repair my car when it breaks down and Chevy says I didn't follow its advice on octane...no warranty coverage.
Sam_Spade
Explorer
Sep 26, 2017
Chum lee wrote:
The engine runs normally without pinging though.

Not all pings are loud enough that you can HEAR it.