A year ago, my then new 2013 Silverado 6.0 pickup was getting about 12mpg and I was not happy. Last Spring it started averaging close to 13 mpg. This fall, with 15,000 miles on the odometer it is getting right at 14 mpg with mixed driving. These are hand calculated between fill ups, not computer generated numbers. I have never had a late model vehicle improve this much as there really is not much break in to do. Anyone else share this phenomenon?

Our diesel kept getting better up to about 15-20k then leveled out.Maybe also you subconsciously changed your diving habits slightly (lighter foot, smoother accelerations, etc.).

downtheroad wrote:Our diesel kept getting better up to about 15-20k then leveled out.Maybe also you subconsciously changed your diving habits slightly (lighter foot, smoother accelerations, etc.).I hear that all the time about diesels, but not gassers. I may be driving a little bit better, although my cruising speed (70 mph) has not changed.

The mileage change you are seeing is not from breaking in. I have no idea what the change is coming from but it's not because of the motor breaking in. BSFC figures just change a handful of horsepower from brand new to fully broken in. And it would take more than a handful of HP to see the improvement you are seeing. 15% is HUGE!There are lots of things that contribute to fuel mileage but the big ticket item when you see a big change in fuel mileage is fuel. It has been reported over and over that some fuel suppliers are cheating on the amount of alkie they are putting in the fuel mix. I have personally seen fuel reports that show a 2 to 3% "difference" in alkie content from station to station around here. Others have reported that they have seen a 10% difference.Another BIG ticket item is driving habits. When something is brand new most people have a: "lets see what this puppy can do" attitude even though they don't want to admit to it. After they have their car of truck for a few years that changes to a "no big deal" attitude and the mileage gets better. With big HP engines we see now days is just astounds me how much fuel an engine will use when I flooring it once or twice a tank full. At full throttle one of the cars I drive uses about 5 gallons of gasoline per mile driven. :E

My 2014 Dully (in my signature below) has less than 5000 miles now. I've not even done the first oil change. But the mileage (diesel) has improved since I first got the truck. It started at 10 mpg and it's now averaging about 15. Open highway, (long distance driving, not interstate, and towing) it last averaged 16. I was shocked. I think the longer it runs the better it's getting too. Go figure, but I'm NOT complaining. My last Dully averaged 10 mpg when I sold it. I was so disappointed with the new one only got 10 also. But that started changing rather quickly. I *don't* get it, but I sure am enjoying it!

You might want to go on one of the big GM truck websites to see what other owners are reporting. I assume you're running a 3/4 or 1 ton truck since you're talking about the 6.0--not the 6.2. Those running 6.2's in 1/2 ton trucks brag about their power--and getting 1 mpg less than a 5.3 1/2 ton truck.The Ford F250's with the 6.2 gas motor commonly report 14 mpg in town and 17 mpg on the open road--without carrying loads.My son in law has a 6.0 3/4 ton pickup, and his fuel mileage has been dismal. What I don't understand is why he's just accepted it. I'd at least want to get the engine checked out on a high level scanner to make sure the truck's in perfect mechanical position.

How good will it get? | Good Sam Community

17 Replies

Tystevens
Explorer
Sep 29, 2014
mtofell1 wrote:
Don't forget about winter/summer fuel blend differences. I see around 1 mpg drop with the ethanol in the winter fuel. Not sure if this is done in every area or not.

I was gonna say the same thing -- the OP might expect to see a drop here in the next month or so when fuel changes over.
mtofell1
Explorer
Sep 26, 2014
Don't forget about winter/summer fuel blend differences. I see around 1 mpg drop with the ethanol in the winter fuel. Not sure if this is done in every area or not.
CptnBG
Explorer
Sep 26, 2014
I had the opposite experience. My best mpg was when my '03 6.0 was nearly new, 15mpg interstate driving. I contribute it to non ethanol gas. Now it is nearly non-existent where I travel. Now I'm lucky to get 14mpg.

Another big factor with my truck (4.10) rear end, is speed and rpm. traveling @ 55, I consistently get over 14mpg, 65-70 I get 12-13. Hauling the truck camper, I get 10-11 mpg.
edm3rd
Explorer
Sep 26, 2014
I had the same experience on worn tires. 245/75-16 lost a full 1" in diameter, and weren't down to the wear bars. Check your odometer (at least 50 miles) either by mile markers or GPS. I re-calibrate my ScanGauge about every 10,000 miles to maintain accuracy. With brand new Michelins my truck odometer was still off 2.2%
lbrjet
Explorer
Sep 22, 2014
Tires getting worn in. I got my best mileage ever last winter with 55K on my tires. Replaced them (with the exact same tire) and immediately MPG went down. Now at 72K and mileage is going back up again.
APT
Explorer
Sep 22, 2014
My 2011 GM 6.0L improved a bit over the first 20k miles too. I was getting about 12mpg commuting and now my wife hovers over 14mpg. We have had as high as 18mpg over whole tanks on long trips. Towing is 8-10mpg.
kw_00
Explorer
Sep 21, 2014
Wow getting off track and into a pi..sing match, don't need that. Anyway to the other poster about his son in laws 6.0 getting bad fuel milage. Yep I agree with u, he should get it checked out. I know that my truck is not really fuel efficient by any means but good for a HD gas truck. Pass him the numbers I stated that I'm getting hand calculated. He just may make a trip to the dealer afterwards. One thing I noticed though... Some gas in the winter months (if u call it that in Florida) getting slightly less in mpgs in my truck. Maybe his is similar.
TomG2
Explorer
Sep 21, 2014
Even Nascar engines putting out 800-850 horsepower get many times the mileage you mentioned, usually 3-5 mpg. Of course none of this extreme usage has any relevance to the vehicles we use to tow our trailers. Your example is meaningless. As is mine.

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Too many smart alecks, not enough wisdom.
Turtle_n_Peeps
Explorer
Sep 21, 2014
TomG2 wrote:
Turtle n Peeps wrote:
...snip........ At full throttle one of the cars I drive uses about 5 gallons of gasoline per mile driven. :E

Lots of fuel mileage comments on the forum, but I believe 0.2 mpg is the lowest reported. How fast are you going at the end of that mile, about 250 mph?

750 HP and 142 MPH at the end of a 1/4 mile. Needless to say it can use a lot of fuel.

My point is, even stock engines in tow trucks can use a lot of fuel these days if you use the horsepower they have. All major brands 1/2 tons are over 400HP now. Not many years back truck engines were less than 200HP and could only flow that much fuel.

A lot of things cause substantial better mileage but breaking in isn't one of them.
TomG2
Explorer
Sep 21, 2014
I have owned many many new pickups and this is the first to show much improvement after a few thousand miles. Wondering if perhaps I had a brake dragging or some other rough spot in the drivetrain that might have smoothed itself out? Not complaining, just wondering.