Hello all,

I've put about 12,000 miles on my truck in just over three months, mostly highway, but since I live between Chicago and Milwaukee I get a lot of unwarranted city driving as well.

Current Results:

City: 17.5 mpg

Highway w/cruise: 21mpg
Highway w/out cruise: 22-24mpg

This is on a 13' Sierra Z-71 5.3 with AFM. The trick to getting the higher mileage is to feel the v8 drop down to v4 and then try to nurse it and keep it from kicking back in. IMO they could create an eco mode that prevents the v8 from coming on at unloaded 65+mpg and see 25-30mpg- but I'm sure they don't want customers complaining that their truck doesn't have enough power when they forget to turn ECO off.


Anyways, I finally manned up and put ethanol (E85) in my truck today. (All of the other pumps were being used). On my short 10 mile stint home at 35-45mph the onboard computer read 20.5mpg, but I'll keep you guys updated.

Will the MPG calculator on the truck compensate for different fuel? How does this work? Admittedly, the numbers above are computer numbers as for some reason, THIS TRUCK HAS ONLY ONE FRIGGIN TRIP ODOMETER, and I usually am driving for work.

For reference, Regular was $2.89 and ethanol $2.09. 28% cheaper.

 

no e85 stations in Canada that i'm aware of....so I can't test this. I am interested to see what the results will be.


do you think the trucks mpg calculator is accurate?

 

Your gas mileage for ethanol will not be as good as regular gas. How much I don't know so maybe from a price standpoint it may be cheaper. I don't know how the truck calculator figures mileage out. I suggest you check it the old fashion way and let us know. It would be interesting to see how one tank of gas compares to a tank of ethanol both in mileage and dollars.

 

From everyone I've ever talked to that has used E85, they've all said that they loose a little power and MPG. Also there's a switch over period of 10 miles that you're supposed to drive immediately after filling up. Literally the exact startup after refueling. So fill up with E85, start the truck and drive 10 miles.

Right from the owner's manual: We see it sometimes in the service department where people will have a half tank of regular 87 octane, and then top it off with E85 - that's a no-no! Drive out the 87 octane as low as you're comfortable doing so, then top it off with at least 3 gallons of E85, then on the next startup, the one right as you're leaving the pump, drive the vehicle 10 miles. That 10 mile period the vehicle is in learn mode and is changing it's fuel adapts to allow for a higher concentration of ethanol. After 10 miles, the vehicle will be in e85 mode and you'll be ready to continuously use E85 as needed.

 

Well I was a little worried I wasn't going to make it to the station without running out for a few. The fuel range gets down to 30 miles and then just says "LOW" haha.


After a weekend project, I've run to Menards 4 times and idled a lot. About 40-50 miles in total. Still haven't had it on the highway, but this type of driving would normally give me about 16-17mpg just because of the idling.

Truck currently reads 13.2mpg. IE 20% less

 

Update:

Around town: 14mpg (20% decrease)
Highway: 15.2mpg (28% decrease)

I ran her til it was empty and put regular unleaded back in. While my suspicions were confirmed that it was about a wash, I did not like the way the truck ran. If I let it idle for over 5 minutes it would feel a tad rougher than normal, and it felt like an absolute DOG when trying to merge onto the highway... If I wanted v-6 power I would have bought one lol.

Anyways- here's the results!