Fuel tanks

I believe like all Gm vehicles, they will run with the EPA limits. E-10, 10% Ethanol.
My wife's Envoy, had some O2 Sensor problems and the fuel in her tank was measuring 16%. Dealer told me that Gas may be the issue. I asked them to Re-program the Computer with more of a Variable limit.

The answer was, it can't be done. Mixture is calculated by the Engineers at the design level of the motor, and are calculated based on what the EPA sets as the Nationwide standard. A curve is built into the Equation but cannot be altered unless the designers recalculate and the update is approved by the EPA. It all has to do with the Mixture, and how the engine burns it.
Emmisions Inspections.
???
Sounds like a good answer!

[deserth3]

This is found on page 5-6 of the owners manual.

Gasolines containing oxygenates, such as ethers and
ethanol, and reformulated gasolines may be available in
your area. General Motors recommends that you use
these gasolines if they comply with the specifications
described earlier. However, E85 (85% ethanol) and other
fuels containing more than 10% ethanol must not be used
in vehicles that were not designed for those fuels.

[Linus Gump]

It is required by law to denote when and how much ethanol is in your fuel. There will be a sticker somewhere on the pump in plain view informing you of this, if there is ethanol blended fuels sold at that station. Just buy where it is 10% or less and you will be fine. Try to avoid it all together if you can, though.

[f5fstop]

I thought 15 percent, but it appears I was wrong; do what the owner's manual states. (Personally, I avoid any ethanol...period.)

[RazM]

Originally Posted by f5fstop

I thought 15 percent, but it appears I was wrong; do what the owner's manual states. (Personally, I avoid any ethanol...period.)

Why do you avoid ethanol?