87 octane vs 91 octane

[JonnyTahoe]

Here’s some nice pics....View attachment 190849View attachment 190850

We have 102 Racing fuel at some gas stations in the metro area.

 

[dbbd1]

We have 102 Racing fuel at some gas stations in the metro area.

View attachment 191730

Dang!...

 

[Scottydoggs]

i can get 101 local. its also 11 bucks a gallon, no thanks.

 

[HACK BLOCK]

if the manual says put 91/93 then you should. yea u can run 87 but you'll probably lose performance. there is always gonna be somebody that says they put 87 and it runs fine. I never really understood why someone would buy a car that needs 91/93 and complain about it. I mean would you put 87 in a Ferrari cause 91/93 cost more?

 

[cardude2000]

The engine will adjust but you’ll lose power and mpg. Put in the correct gas.

Don’t worry about engine temps. That myth has been long busted. (Most folks mix up racing fuel and pump fuel which use different methods of boosting octane).


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[GTNator]

We have 102 Racing fuel at some gas stations in the metro area.

View attachment 191730

What metro area is that? And why do they offer racing fuel as a regular product there? Is it close to a popular track?


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[Rocket Man]

I agree that you should run what your owners manual says to run. If it's tuned to run on 87, you won't see much difference in mpg running 91 and you'll be wasting money. If its tuned to run 91 or has high compression and you run 87 you risk detonation or ping and damage. The tuning tables have flexibility but that's designed for differences in brands, not necessarily different octanes. I had the availability of 2 different tunes from BB on my Autocal, 87 and 91. I ran both for several tanks and saw about 1-2 mpg difference which wasn't worth the added cost. But now that I installed the Whipple I have no choice but to run 91+ and my tune is set up for it.

 

[Fless]

Regular octane at high altitude (like Denver) is 85. Less oxygen in the air tends to effectively lower the compression ratio, from what I've heard. I usually run at least 87 anyway, higher when towing.

It would be interesting to actively monitor ignition timing to see if the knock sensors cause timing retardation when running 85. Is there a valid way to do that?

 

[noob]

I run 93 octane almost exclusively. I notice about a 2-3 mpg drop and decreased acceleration on 87 in the past, so I see it as a wash.


Edit: my car is a 6.2 liter escalade that says premium fuel only. Hence your mileage my vary on the 5.3L.

 

[swathdiver]

It would be interesting to actively monitor ignition timing to see if the knock sensors cause timing retardation when running 85. Is there a valid way to do that?

Sure, a good scan tool can see that in real time. The Tech2 can certainly see that.