85 instead of 87 octane at high altitude?

[NissanMaxima]

Hi all: I live at 5000+ ft above sea level. My manual for my 2015 Corolla specifies 87 octane and has no comment for high altitude conditions (unlike the manual for my Nissan). I thought that one can and should use a lower octane at higher altitudes but I also know if most cases the manual "wins".

Thanks for any input.

 

[mclasser]

I have friends in Colorado and they said everyone uses 85 in applications where regular 87 is called for.

 

[Merkava_4]

Being that pre-detonation causes such horrific damage to engine pistons, I wouldn't risk it.

 

[Chris142]

The higher the elevation the less octaine you need

 

[Merkava_4]

What if you need to go down to a lower elevation for some reason ? You're screwed.

 

[john_pifer]

Originally Posted By: Merkava_4
What if you need to go down to a lower elevation for some reason ? You're screwed.


Eh, depends on what vehicle. Most modern vehicles should compensate by retarding timing at the slightest hint of knock.

 

[oldmaninsc]

Originally Posted By: Merkava_4
What if you need to go down to a lower elevation for some reason ? You're screwed.


Only if you still drive a car from the 60's or 70's. If that were the case AND you had to go to a lower elevation - here is a thought, stop at a gas station and fill up with higher octate gas. Problem solved.

 

[skyactiv]

Most auto makers strongly oppose 85 octane gasoline being sold in the mountain areas.

https://dps.sd.gov/documents/allianceofautomobilemfg.pdf

 

[MNgopher]

85 octane is generally fine for any driving in Colorado and most of the high mountain west in vehicles that call for 87 octane . If you plan to drive east out of Colorado, just fill up with some 87 octane if you are concerned.

That's what I did when I lived in Fort Collins. On my truck, I routinely drive from the front range to Eastern Nebraska at elevations below 2000 feet. Never an issue when I fueled up with 87 octane before leaving Colorado.

I'll also note that the issue in South Dakota arose when retailers outside of the high elevations in the western part of the state started selling 85 octane - and that is an issue.

 

[SZR48207]

If the car is still under warranty I would use 87 regardless of altitude. Why give them a reason to try and deny a claim?

 

[NissanMaxima]

Thanks all. I seem to remember that a mechanic told me (or perhaps I read this somewhere) that using a higher octane than necessary can actually be bad in terms of incomplete combustion and deposits. Is there any truth to this? The Toyota dealer here told me 85 is absolutely fine, but if there is no harm with 87 in terms of deposits, maybe I should just stick with that.

 

[AKhan87]

my wife goes to college in Wyoming, she uses 85 octane all the time, she actually gets higher mileage on 85 octane then the typical 87. we have about 10,000 miles of data on it. I see no "power" lost on those STEEP mountain drives, I have yet to see an issue, oil doesn't smell of gasoline either.

I would say it would be no problem on a modern engine, but you have to try it to see.

 

[NissanMaxima]

Thanks! In addition to my other question about potential harm from using TOO high an octane (such as 87 where 85 suffices) that I hope someone from the board can answer, would 87 vs. 85 help with acceleration? I started this thread about my Toyota which we bought here in Colorado, but I have definitely noticed a loss of acceleration in my Maxima after moving from Ohio to Colorado and realize this is from the lower air density, but can one compensate partially with higher octane?

 

[AKhan87]

Originally Posted By: NissanMaxima
I started this thread about my Toyota which we bought here in Colorado, but I have definitely noticed a loss of acceleration in my Maxima after moving from Ohio to Colorado and realize this is from the lower air density, but can one compensate partially with higher octane?
no you can't compensate for it by using a lower octane, one thing is for sure though, the random steep hills in Missouri highways are harder on the engine(power wise, on cruise control it downshifts here sometimes but almost never in the higher elevation) then the higher elevation that is in Colorado/Wyoming on my wife's 01 celica gt.

Note:she also gets +2-3 mpg on 85 octane there compared to 87 here in st. louis

 

[SZR48207]

Originally Posted By: NissanMaxima
Thanks all. I seem to remember that a mechanic told me (or perhaps I read this somewhere) that using a higher octane than necessary can actually be bad in terms of incomplete combustion and deposits. Is there any truth to this? The Toyota dealer here told me 85 is absolutely fine, but if there is no harm with 87 in terms of deposits, maybe I should just stick with that.


No harm to use higher octane fuels, except to your wallet. I can see how people would think a higher octane could cause incomplete combustion but that's not the same thing as being resistant to pre detonation.

 

[TiredTrucker]

Originally Posted By: skyactiv
Most auto makers strongly oppose 85 octane gasoline being sold in the mountain areas.

https://dps.sd.gov/documents/allianceofautomobilemfg.pdf


But a quick read of that article was talking about ENTIRE state of SD. Sioux Falls, for instance is lower elevation. Not a whimper of higher elevations even mentioned in that article. While on the surface, the argument is valid, but it is myopic. Higher elevations with lower air densities, octane is not as critical.

 

[MisterBen]

Just a point of reference, sample of 1...

We used to be in WA, and moved to the front range in CO a few years back. We live at about 6,200 ft. I never really gave it much thought, but the Toyota manual says to use 87 or higher all the time.

We were using 85 for a while, because I always thought it didn't matter. After a while, the vehicle started running worse. Less power, just not that great. The vehicle is a 2012, so it's not an age issue.

We went back to the much more expensive 87, and the vehicle is back to running like normal. I can't tell you why, but I'm fairly certain it was caused by the fuel. We ran both for long enough to know it was not a short-term issue.