Help! Struggling to break 11 mpg

[TimmyG]

Your still breaking it in! My gas mileage got better till 18,000 miles

[KARNUT]

My second winter, 13-14 mpg with warm ups in town on E 85. Two to three miles per gallon better on gas. That's in south Texas

 

 

Sent from my iPhone using Tapatalk

[huggytree]

mine has about 700 miles on it and im averaging 14.5 mpg.....mine is in a heated garage, so no warm ups

 

we are stuck with ethanol blended gas here, so i assume thats 1-2 mpg reduction

 

i watched the actual mpg while going up hills...and it was 8mph...going down the hill...22mpg.....

 

my 13,000lb gmc cube van 6.0 liter gets 8.5 mph, so i was shocked to see the 5.3 in a truck can get down to 8mpg w/o flooring it...just gently going up a hill

 

so far my mileage has been depressing.....we traded in a Chevy Traverse that got 15.5mpg and were hoping for 17+

[Ventilator]

I live in MI, and the worst tank I have had all winter is 17.1, hand calculated. This is on 87 octane, 10% ethanol, winter blend gas. I get between 21.5 and 22.5 average in warmer weather. 5.3 SLE Double Cab with 3.42 gear ratio, Z71 high capacity air cleaner. All Stock GM tune.

 

I don't do a lot of city driving, mostly rural 55 MPH 2-lane highways, and some small towns thrown in that reduce you to 25 MPH. I do remote start my truck before leaving work, and the low temps have been bitter cold (10 F to -30F) over the last month. Been warming up over the last couple days, and we might just have this cold spell licked?

[Imcrazy]

My 4.3L got better after a few 1000 miles. What do you typically have the transfer case set for? Are you letting the truck warm up for several minutes before you leave?

 

If I run 4x4 or auto a lot and let the truck run for 10 minutes before I leave for work and again when I leave to head home, I get like 14 mpg in this weather. Also run GOOD gas, don't get your fuel @ sams club or costco, I lose 2 mpg when I run that crap fuel compared to speedway, mobil, marathon etc. I'm guessing you have a 3.42 rear end?

 

On summer mix gas I get about 19mpg driving back and fourth to work, which is suburban 35-45 mph roads with a few stop lights, switch to winter mix and I get more like 16-17 if I mostly run 2hi and don't remote start. You gotta remember when your idling you get 0 mpg!

[redwngr]

I've got a 2015 Sierra crew cab, 5.3 liter. Driving mostly city miles, just rolled 1000. I'm not hard on the throttle, I've tried 87 and 89 octane. I even tried to drive as conservatively as possible to keep it in v4 as much as possible for an entire tank. Doesn't change, I get somewhere between 10.4 an 10.9 per tank. That's actually resetting the trip meter and calculating with actual fuel going in the tank. The last 25, 100, 400 reflect numbers pretty similar, maybe a little lower than I calculate, but real close.

 

Any thoughts? These numbers are nowhere near the estimates. Had I known this going in, if this is how it's going to be I never would have gone this route. MPG is one of the big reasons I went with the Sierra over the tundra.

 

Hope someone can help

How long are your trips?

Long enough to get it warm?

They do behave different til engine and transmission are warm.

 

It does sound to like the mileage is abnormally low.

[SouthernSilveradoGuy85]

I didn't realize I didn't mention this in my 1st post. But how about your tire pressures? Having unequal pressure between all 4 tires will lower the mpg and also even ig they're equal the lower the psi the worse your mileage will be. I usually run about 40 psi even though the TPMS reads 38. 32-35 seems to be the psi more for cars or smaller trucks. A full size truck, especially one with a decent about of sidewall, seems to need a little more because 35 made the tires look too low. You have to find the sweet spot, more psi will help mpg but will give a little rougher ride while a little less psi will ride better and grip the road better in corners but will wear tires faster.

[hammonss]

I replaced the stock tires with Michelin ms2 and run them at 34psi. Maybe I should try to up the pressure a little. I'm only driving 5-10 miles per trip so they're not long.

[SouthernSilveradoGuy85]

I replaced the stock tires with Michelin ms2 and run them at 34psi. Maybe I should try to up the pressure a little. I'm only driving 5-10 miles per trip so they're not long.

 

That means it doesn't really give the tires much time to heat up which would raise the tire pressure. I would go up to the higher 30s like 38 first and maybe slowly add more psi until it's to hard of a ride. I sure wouldn't go above 42-45 because you have to give the tire room to heat up where the psi will go up. I remember getting a new set of tires on my old truck which had 16s and they put 50 in them so I had to let some out. Just make sure you adjust tire pressure after the truck has been sitting or after only a short drive where the psi hadn't built up. I usually have to drive about 5 minutes to where there's free air from my house and never had problems with the psi.

[ToesonTheNose]

i avg about 21 mpg. city driving

[redwngr]

I replaced the stock tires with Michelin ms2 and run them at 34psi. Maybe I should try to up the pressure a little. I'm only driving 5-10 miles per trip so they're not long.

5 mile trips in very cold weather and it likely doesn't get the trans or the engine up to temperature. Economy will be like an older vehicle running with the chock on.

Take it for a 30 (or 50) mile drive and see if the 25 mile average improves to a more normal range.

[SouthernSilveradoGuy85]

i avg about 21 mpg. city driving

 

Well I'm sure you do since it looks like you live in Florida lol. I remember when my cousin from FL would come up here to NC to visit for Christmas and he would keep his big jacket here. I bet 40-50° feels cold for you lol.

[fbachman]

This is consistent with my '07 5.3. Summer suburban driving yields approx high 14s to low 15s mpg. Straight highway at 70mph approx 18mpg. 55mph = 20mpg +

 

Winter, using Auto and 4WD + cold weather + auto-starts = 12-13 mpg, sometimes even less than that--- especially whith AM temps in the -5F range. This is with an aftermarket calibration.

 

As mentioned above, winter gas + cold air also decreases fuel economy, all other things being equal, for reasons cited above.

 

Now, the reality is that the factory calibrations are such that they are completely emissions centric--- i.e. so the vehicle can meet emissions. Performance is secondary, at best. Not to mention the TCM shift settings, especially with 6+ speed autos. They are calibrated to pamper the drivetrain.....(100,000 mile powertrain warranty)...... again, not performance friendly. Not mileage friendly either. Add it all together, and, ... well, ..... you get the picture.

 

My aftermarket calibration turned AFM off. I never saw a difference in mileage with AFM on or off. I believe AFM maximizes MPG on the EPA test cycles that are run to establish MPG numbers for the manufacturer. I don't know if you've ever seen an EPA test "mule"/vehicle, but it is hardly real world and looks like a rat with a frame, electric instrumentation wire- afro and wheels (at least they used to). Been out of the automotive world for some years. In the real world, it makes no diff what-so-ever, even on the highway, thus, I turned that AFM "feature" off.

 

Aftermarket calibrations will help this (MPG) a little with HUGE benefits to performance and drivability. But, the reality is, these are BIG TRUCKS with beefy motors. Aerodynamics resemble that of a barn door. It's just physics and $hit. They will burn fuel, especially in the cold, and when engaging 4WD --- a lot more mechanical crap to turn.

 

Just is what it is I'm afraid. Part of the "cost" of owning a full size truck with all of its other benefits (which, IMHO way outweigh MPG),