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85 vs 87 Octane

Frank Fontana

By Frank Fontana
in 6.6L Gas V8 (L8T)

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Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
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. 

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diyer2 Senior Enthusiast

diyer2

Posted
Posted

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.

  • Like 2
Ray Pickle Enthusiast

Ray Pickle

Posted
Posted

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.

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  • 1 month later...
greatmizzou Enthusiast

greatmizzou

Posted
Posted

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. 

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