Hi. I just bought a used (2008) Suburban LT with 170k miles on it. It is in really nice condition and everything seems to work well, but I do have a question.

It has a FlexFuel decal on the back and the dealer told me I should have no problems running it on 85 or 87 octane gas - is that correct or should I treat it to something a little better? Got to tell you I'm hoping you say it's fine because this thing is a guzzler compared to my other vehicles, but if I need to treat it better I want to know now before I cause any problems.

Thanks in advance for any info you can give.

 

Our 05 has guzzled regular unleaded for over 200k miles; believe that's what the owner's manual calls for. 15 mph daily driver; up to 18 on the highway

 

Welcome to the forum.

Regular is just fine. Higher octane is s waste of money.

 

Well, if you want to have some fun, go find a station that sells E85, and put that in the tank. Might drop your mileage into single digits!

Regular unleaded is fine for your truck. The 6.2L engine in the Denalis needs premium.

 

I've only ever used 87, used 93 a few times when I owned a bully dog tuner. Where are you that you have 85 octane? I don't think I've ever seen that level of octane ever, lol.

 

Thanks all for the speedy responses, and to the question about where I live to get 85 octane ... Utah. I just moved here last year from New York where you could only buy 87 or higher.

I'm not sure why that is, and it's not all gas stations, but it is the cheapest I've found here in southern Utah. I filled up (an empty tank, thanks used car dealer!) at a cost of $2.25 a gallon for the 85. Most of the gas stations around me are around $2.40 a gallon for 87, and up.

 

Do you mean E85? Which is 85% Ethanol... which the truck can run I believe.

It's not 85 octane...

Skip the Ethanol fuel, the cost never makes up for the MPG. Not to mention several people have had their trucks never run the same after a tank of E85...
Hey! let's make FUEL from a FOOD. Genius.

 

Mountain states like Colorado and Utah have regular gas that is 85 octane, due to the thinner atmosphere. Premium gas in those states is 91, also 2 points lower than normal.

 

I never knew

Maybe the electricity has a few less electrons too

 

The thinner atmosphere dosen't matter with fuel air ratio, unless your still running a carb.