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Discussion Starter · #1 ·
I drive a 2011 gmc 3500 SRW crew cab short bed with bed cover.

My father drives a 2013 2500 crew cab long bed with no bed cover.

My fathers truck according to DIC gets 15mpg average around town and approx 20+ on hwy and has a total range of 500-600 miles with a full tank according to the DIC.

With my 2011 the most the DIC has read was 13 mpg after resetting. With a full tank I get a range of 400-450 miles.

So my question is why is my dads LML getting much better fuel mileage then mine?

2011-72k miles
2013-195k miles
 

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I drive a 2011 gmc 3500 SRW crew cab short bed with bed cover.

My father drives a 2013 2500 crew cab long bed with no bed cover.

My fathers truck according to DIC gets 15mpg average around town and approx 20+ on hwy and has a total range of 500-600 miles with a full tank according to the DIC.

With my 2011 the most the DIC has read was 13 mpg after resetting. With a full tank I get a range of 400-450 miles.

So my question is why is my dads LML getting much better fuel mileage then mine?

2011-72k miles
2013-195k miles


the bed cover may actually be negatively impacting your mileage by increasing drag on the truck. normally there's a big high pressure pocket in the bed behind the cab that extends the boundary layer over the tailgate, adding the cover changes how that pocket forms and you get the boundary layer hitting the bed cover causing drag. It could be a lot of other things, but that all that stands out without more info on the differences between the trucks.

Other things to consider:

additives used
fuel source
tank size
his engine is more broken in than yours
state of the emissions systems
lack of emissions systems
tuning
tire size, type, geometry, width etc.
driving habits (lead foot like me)

you could go on and on trying to chase down a 2 mpg difference. If the bed cover is easy to pull off though... id take it off and run the truck through a tank and see if the mileage changes. I would bet that it improves to some degree without the cover.


You guys should switch trucks for a week, and then compare again.

thats a good idea too, will rule out the lead foot issue.
 

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Discussion Starter · #4 ·
Interesting, I was always told the bed cover is better for mileage but I will give that a shot. Im mostly concerned with why his full tank has much longer range then mine. Just yesterday we both had exactly 3/4 of a tank and his range was 430 and mine was 270? Like I said when I’m full I’m lucky to see over 400 miles range. He had 430 at 3/4 tank. I know my emissions system is older and I’ve have plenty of trips to the dealer about that but that’s a different story for another thread
 

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My bet it is it's the way they are driven. Stops/starts. Length of trips. Amount of time at steady speed vs accelerating/decelerating a lot. What type of traffic conditions. Are you both in traffic that it is possible to anticipate need to get of pedal and coast so as to not have to use brakes and come to a stop. Same fuel source? etc etc etc.

Don't put to much faith in fuel range estimate at a given level in fuel tank.

Might be better to compare range shown + miles so far on trip -- for total tank range.
@AlisoBob has the best idea.
Using same fuel?
Fill 'em up and drive for a week. Refill and record. Switch trucks for the next week. Refill, record, and compare data.
 

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the bed cover may actually be negatively impacting your mileage by increasing drag on the truck.
The trucks that I have seen that race at Bonneville have a 2/3's bed cover, with the 1/3 that's missing directly behind the cab.
 

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Interesting, I was always told the bed cover is better for mileage but I will give that a shot. Im mostly concerned with why his full tank has much longer range then mine. Just yesterday we both had exactly 3/4 of a tank and his range was 430 and mine was 270? Like I said when I’m full I’m lucky to see over 400 miles range. He had 430 at 3/4 tank. I know my emissions system is older and I’ve have plenty of trips to the dealer about that but that’s a different story for another thread
in some situations it might work out better, but for daily driving on the highway, no cover, tailgate installed and up is the best MPG. with the tailgate up and the bed open, the air stream coming over the roof of the truck will fall off behind the tailgate. If that air stream ends up interacting with the truck sooner than that, it will result in additional drag on the vehicle.
 

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Discussion Starter · #8 ·
Thanks for the tips. On my next road trip I will fold my bed cover up and see if that makes a difference. I do long trips to Canada from Long Island NY and get about 15-17 mpg doing 65-72mph empty. Towing 5-6k I get anywhere from 9-13 which seems very low for a light load
 

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Thanks for the tips. On my next road trip I will fold my bed cover up and see if that makes a difference. I do long trips to Canada from Long Island NY and get about 15-17 mpg doing 65-72mph empty. Towing 5-6k I get anywhere from 9-13 which seems very low for a light load

my 62 mile highway average is around 23 mpg at 70 mph based on the DIC. That is unloaded besides myself and some work equipment, but nothing heavy. This photo was taken mid way through a 300 mile drive through hills. Its really amazing what a little weight reduction from the front end of the truck does for MPG.
 

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You guys should switch trucks for a week, and then compare again.
^^THIS^^

And dont go by the DIC. Hand calculate.

And yes mileage can vary widely on these trucks. Just the nature of the beast. A lot of it has to do with emissions and how often the truck goes into regen.
 

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Especially when you reset the ave mpg you’ll either get a fantasy mpg on the highway or a disappointing mpg with in town driving.
So many get on a highway reset it, then think there’re actually getting that high of a mileage.
Full up, top it off, reset the ave mpg, miles driven, and drive 300-400 miles.
Then fuel up, topping it off, check your miles driven and gallons used on your DIC, then compare that to the gallons it took to fuel up with the DIC.
Hand calculate the true mpg and compare that to your fantasy DIC mpg.
More than likely you’ll be :| on the true results.
 

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Especially when you reset the ave mpg you’ll either get a fantasy mpg on the highway or a disappointing mpg with in town driving.
So many get on a highway reset it, then think there’re actually getting that high of a mileage.
Full up, top it off, reset the ave mpg, miles driven, and drive 300-400 miles.
Then fuel up, topping it off, check your miles driven and gallons used on your DIC, then compare that to the gallons it took to fuel up with the DIC.
Hand calculate the true mpg and compare that to your fantasy DIC mpg.
More than likely you’ll be :| on the true results.
i think in this case that there is a valid reason to consider all 3 numbers. While your hand calculated average gives you a good idea of what it costs to drive your truck on a day to day basis, the highway reset allows you to see your milage on the highway. So if you were to take a long trip, and you wanted to ball park your fuel costs. Using this number would be more accurate than using your hand calculated average since that would include city driving that you are not doing on this trip. The same can be said for city average. If your driving through LA in rush hour traffic, you probably dont want to base your fuel costs on your hand calculated or your highway averages. It just depends what your trying to use the numbers for. I do agree that the hand calculated is likely the more useful value day to day, but there are good reasons to also use the DIC numbers.
 

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Sure if your just looking for fantasy mpg number.
The dic mpg is just something to view on your dash, giving you a kinda sorta mpg, most of the time not even close.
How I calculate trip mileage is to fuel up and keep fueling up when needed, until you’ve reached your destination, then average.
No matter the amount of fuel you need, you’ll need it.
Mine if I only went by in town driving I’d be lucky to ave 8-9 mpg, it’s best to not know in town only.

This ave dic mpg has just caused more confusion for the ones that don’t know any better, fantasy and passing the fantasy on as actual mpg when they post.
The slightest grade up or down will affect the instant mileage, stop and go, idling will affect mileage when your constantly resetting it.
If you want fantasy then watch a Disney movie.
 

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No, Do NOT use “fuel used” from the DIC. Use the readout on the gas station pump.

“Fuel used” is typically where they are off giving inflated MPG numbers. Fuel used on my truck is consistently 5-7% less than what the pump reads each time I fill up.

Its been consistent the life of the truck. Some truck are pretty damn close to hand calc and some are not. Either way you need to compare a few tanks that are hand calculated to know where your truck sits. I no longer hand calculate because I know how much mine is off by and can do the adjustment in my head.
 

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I hate to disappoint J83, if your going to take a trip figuring the amount of fuel needed and going by the instant ave mpg re-setting on the highway, you'll come up way short with your fantasy figures.
If the person was naïve enough to plan on going with that figure out he'd come up short and run out of fuel if he didn't plan on extra expenses needing to buy more fuel.

At least if you go by the average mpg hand calculating tank to tank they should have enough fuel to make it with a little left over to drive to someplace special for eats, without being embarrassed running out of fuel and money by taking this riduclas fantasy mpg advice.

After installing my aux tank if I end up transferring fuel, I won't even bother hand calculating also I haven't even reset the dic mpg its been on 12.7 for about one year.
For kicks I might check and divide gallons into miles driven, mine has always been anywhere from 1 - 1 1/2 gallons less put in than what the dic shows. Which means my actual real live mileage is a little better than the dic.

But I have for fun done this resetting the mpg dic on a flat highway set the cruise @ 70 "BAM" I'm getting 21.7 mpg for a few minutes at least up until I'm going up a small incline, then it drops like I'm dragging a anker
 

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Doesn't the long bed have bigger tank than short bed?
 

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Doesn't the long bed have bigger tank than short bed?
No LML (2011) got the bigger 36 gal tank. BUT that is beside the point as tank size has nothing to do with what MPG your getting
 

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I don’t know many people that solo travel that doesn’t do any in town driving where ever they go.
Towing staying at a RV park more than likely you’ll unhook then head to “Billy Bobs TEXAS” for a few rounds and dance maybe even get drunk enough to ride one of those bulls.

Dry camping would be driving around in my Polaris Ranger, truck setting pretty much until we’re packed up and ready to leave camp.
 
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