Mileage Recovery After Flex Fuel

[Schimpfy]

Hi, all. First post so go easy.

I purchased a 2010 Yukon SLT back in March as an upgrade from my wife's '97 Suburban. Family and I were coming back from Texas to Ohio and decided to try E85 on our last fill-up since it was over a $1 cheaper than 87.

Obviously, there's a rather large decrease in mileage. I went from 17.5 mpg to 10ish mpg with the E85. How long does it take to recover that lost mileage after switching back to regular gas? It's been a couple of months and it only seems to be back up to 13.5 mpg average.

This is my first experience with such a new vehicle so any help would be appreciated. Thanks!

 

[swathdiver]

Hi Michael and welcome. With only one tank, your mileage should not have decreased much in the first place. E85 when mixed with the last 4-5 gallons will usually settle somewhere in the 50-70% range. It takes 2-3 tanks of gasoline after switching off E85 to get the alcohol content back to normal.

But sometimes Michael, the computer can get confused, especially if the truck was fueled and not driven for at least seven miles before shutting it down, the alcohol content can be off and that will tank the mileage. You may need your Fuel Trims and Alcohol Content reset. This can be done with a Tech2, the same computer the dealership uses.

The mileage figures you are reporting, are those city, average driving or highway?

 

[Schimpfy]

Thanks for the reply.

The mileage is an average with a good mix of both highway and city driving. I'm a bit confused by the next part of your post. Are you saying that if I filled up, drove less than seven miles and shut the Yukon off it could screw with the computer? If so, that wasn't the case here. After the fill-up I drove straight from Cincinnati to home, about four and a half hours so I think I'm good on that front. How much might dealers generally charge for this?

 

[swathdiver]

Thanks for the reply.

The mileage is an average with a good mix of both highway and city driving. I'm a bit confused by the next part of your post. Are you saying that if I filled up, drove less than seven miles and shut the Yukon off it could screw with the computer? If so, that wasn't the case here. After the fill-up I drove straight from Cincinnati to home, about four and a half hours so I think I'm good on that front. How much might dealers generally charge for this?

Yes, it's possible. Some folks on here have reported poor mileage and discovered that their alcohol percentage was off and had the dealer reset it. Do not remember the cost but I reckon it should not be much more than an hour's labor.

Your truck's mileage on gasoline is 15 City, 21 Highway and 17 Combined. On E85 it is 11 City, 16 Highway and 13 Combined.

On Fuelly's website, the 2010s have the highest average mpgs at 15.18 mpg for all model SUVs. The average MPGs reported for all GMT900 SUV of all years is 14.3 mpg.