2011 GMC SIERRA SLE INPUT

I have a 2009 Silverado with FlexFuel and I STILL hate ethanol and won't use it where I have the option for real gas.

I own a 2009 GMC Sierra SLE with the active fuel management and Flex fuel option.  Flex fuel is somewhat of a joke as it has to be roughly one dollar cheaper just to break even.  There are many websites that run through the conversion with E-85 fuel and reduced mpg's.  Maybe things have changed for the 2011's but I don't ever forsee myself using the E-85.  With the AFM setup i'm getting 18 mpg's although I'm usually towing a boat with it.  Hope this helps.

I've sold these vehicles for 13 years now and would not recommend using E85.  My first experince was a Ford Taurus.  Cut my mileage right in have and developed an engine ping that never came out.  When a vehicle is equipped with E85 capability the engines are alluminum, the fuel lines are either made of alluminum or stainless steel, but the valves are made of "hardened steel".  This fuel is highly corrosive.  That's why you need alluminum and stainless steel.  Rubber hosed fuel lines disintegrate and cast iron blocks corrode.  Then that leaves the "hardened valves"(the part that can corrode). You can put this fuel on a razor blade and watch it rust.  The manufacturer says its safe.  It's your decision of course but I wouldn't touch it after the things I've seen. 

I don't own a flex fuel vehicle, but what I hear from friends is much of the same.   I've talked to enough mechanics that tell me anyone who runs E85 is asking for trouble.  I'll take their word for it. 

I've tried in my Chevy, but will never do it again. The mileage sucked and like said above, it's gotta be about $1 cheaper to break even. Also noticed power lose and it would hardly ever kick down to 4 like normal, always ran at 8.

The 4.8lit is a dog,driving one right now,company vehicle,I get better milage with the 5.3lit engine and the 6 spd tranny.

Tim

I have a 2011 GMC and agree completely with Tim.  The 5.3 gets solid mileage and plenty of power.  I average 18 mpg on the highway, 13-14 towing my boat.  I ran exactly one tank of E-85 to try it out.  That monkey pee will never touch my truck again.  Bad power, bad mileage.  I try to run no ethanol whenever possible.  The truck runs better, gets better mileage and more power on straight gas.  The 6 speed tranny is a very nice upgrade over the tranny I had in my '03 GMC.

brotsky Said:
I have a 2011 GMC and agree completely with Tim.  The 5.3 gets solid mileage and plenty of power.  I average 18 mpg on the highway, 13-14 towing my boat.  I ran exactly one tank of E-85 to try it out.  That monkey pee will never touch my truck again.  Bad power, bad mileage.  I try to run no ethanol whenever possible.  The truck runs better, gets better mileage and more power on straight gas.  The 6 speed tranny is a very nice upgrade over the tranny I had in my '03 GMC.

Looking at some older trucks.  What mileage did you get with you 03?

I got 17 pretty consistently.  That '03 was a great truck, 150k on it when I got rid of it and never a problem other than a couple minor things, IE wheel bearing etc...I'd still have it but with three kids to haul around a crew cab made more sense.

brotsky Said:
I got 17 pretty consistently.  That '03 was a great truck, 150k on it when I got rid of it and never a problem other than a couple minor things, IE wheel bearing etc...I'd still have it but with three kids to haul around a crew cab made more sense.

with the 5.3 in it?

mv,

My apology,I missed the part that said "I bought" did'nt want to talk down your new ride,actually the 4.8 will do ya fine if you keep your foot outof it,it has more Hp than the old 350's,I'm just use to the 5.3's.Goodluck,and as far as the trailer package goes,make sure its factory and not a dealer install~Factory will give you the locking diff and engine and tranny cooler plus a heavier suspension.

I get 17 mpg on the highway at 80 with my 6.2 liter.  In fact, on my recent trip to ND over 1500 miles, If I take the highest mpg (17.8) and the lowest (15.2)  and throw them out, I got an average of just over 17 mpg with the cruise set at 80mph on all interstate driving.  The 15.2 came when we were detoured in NE and MO due to flooding.

Ice Man Said:
I get 17 mpg on the highway at 80 with my 6.2 liter.  In fact, on my recent trip to ND over 1500 miles, If I take the highest mpg (17.8) and the lowest (15.2)  and throw them out, I got an average of just over 17 mpg with the cruise set at 80mph on all interstate driving.  The 15.2 came when we were detoured in NE and MO due to flooding.

I bought a Crew with a 6.2 about 2 months ago and am in love with that motor.  The only down side is that it gulps a little harder around town than my old 5.3.  Highway is about what you are seeing, but not at 80( more like 70 but it only has 4000 miles on it).  The 400 ponies make me grin like a little kid.

Oh yeah, and to keep with the thread......I also hate E-85.  You got less power and your fuel gauge goes down like somebody cut a hole in your gas tank.

E85 does not give you less power. If you read your manual you will actually see that on most vehicles the highest power rating comes with E85. Heck, my wifes 8 year old Taurus even says to expect about a 5% power increase when using E85. In the F150s, it was actually noticable. I gusss I cann't say for sure on the GM counter parts if this is the case however I would expect it to be since the timing can be increased due to the higher octane.

yes if everything is in good working order more power can be achieved with e85 but the fuel effiecency is crap...

Oh and Ahab those 6.2s are beasts!!! My brother had one and my dad has one right now and they really haul the mail. Mileage was 17-18 under good highway driving conditions.

YarcraftStorm Said:
E85 does not give you less power. If you read your manual you will actually see that on most vehicles the highest power rating comes with E85. Heck, my wifes 8 year old Taurus even says to expect about a 5% power increase when using E85. In the F150s, it was actually noticable. I gusss I cann't say for sure on the GM counter parts if this is the case however I would expect it to be since the timing can be increased due to the higher octane.

I have read that, but that did not seem to be the case with my 2009 5.3 ext-cab GMC.  Seat of the pants feel was less power, maybe that is peak rpm power and not in lower rpm ranges?  I pulled my boat with it in once and I could have just as well poured it through my engine.  Mileage like a big block motorhome.

jdjacobson Said:

brotsky Said:
I got 17 pretty consistently.  That '03 was a great truck, 150k on it when I got rid of it and never a problem other than a couple minor things, IE wheel bearing etc...I'd still have it but with three kids to haul around a crew cab made more sense.

with the 5.3 in it?

Yes, this was all in driving meaning around town, etc.  On the highway it was better, at least 18 and I had gotten close to 20 with it on a few trips.  You could count on 18 though, better if you don't have a lead foot.  LOL! 

Hell when e85 was $2/gal two years ago and 87% was $4/gal I would blend the fuel every other tank,either 50/50 or 60/40 just to get the volume up,kept my speeds under 65mph and only lost 2-3mpg's to and from work,helped the pocket book forsure,pulling my boat just used 87%,worked out great.