85 vs 87 Octane

[Frank Fontana]

Hey all, I know that 87 is the “recommended” octane, but has anybody run 85? Any issues?

[Bob 3500HD]

You at high altitude?

[Grumpy Bear]

26 minutes ago, Bob 3500HD said:

You at high altitude?

 

85 is prevalent in the Rocky's

 

9 hours ago, Frank Fontana said:

Hey all, I know that 87 is the “recommended” octane, but has anybody run 85? Any issues?

 

https://www.sae.org/publications/technical-papers/content/872160/

 

A point to a point and a half per thousand feet in elevation. 

[diyer2]

If you are at altitude and 85 is available, use it. I used it for years here in Colorado. Now that I'm retired and don't drive as many miles I use 87. All my gas engines recommend 87 in the manual. 

Using Top Tier gas is a good idea IMO.

[Ray Pickle]

Used 85 when in altitude in Colorado last month while towing 12k fiver, there was no noticeable difference in power or mileage. Thats why it exists. I would not use it at low elevations nor do I believe its generally available at low elevations away from mountainous regions? "E85" being the exception and new gasser is not designed to run on that.

[Frank Fontana]

Yep I’m in Colorado, sounds like 85 is the way to go, thanks all!

[Frank Fontana]

13 hours ago, Bob 3500HD said:

You at high altitude?

Yep, Colorado 

[greatmizzou]

My beat up 5.3l v8 was pinging with 85 octane towing a 4500sh lb camper.  I filled up with 87 and it was fine.

 

That happened when I was driving up in the mountains west of colorado springs.  
 

On a newer motor perhaps its less of an issue, but imo i put in what the manual tells me to.