[Caper11]

If you want to track fuel economy, it might be useful to use one of the trip meters and reset it each time you fill the tank. (it rests both the trip distance and the trip fuel economy)
And if a long term log is desired, record the trip meter numbers and fuel added at each fill.

(I set the 2nd trip meter so it doesn't display so it doesn't accidently get reset. It then keeps track of 'life of vehicle' fuel economy)

I often have one (the 31mile / 50km one) of little best/average/instantaneous pages up to get an idea how mileage changes with driving conditions. ('inch' unit trucks have a 25 mile one)
The 'average' and 'instantaneous' give an idea how current usage compares with the usual tank averages.

imho, the 'best' numbers are of passing interest as they are typically obtained under conditions that may not be often repeated.

Yep I use the trip meter to track the distance driven.
I find GM’s fuel economy system is a joke actually, it’s worse than Ford. Hand calculating is the only true way of getting your trip fuel mileage.


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[redwngr]

Yep I use the trip meter to track the distance driven.
I find GM’s fuel economy system is a joke actually, it’s worse than Ford. Hand calculating is the only true way of getting your trip fuel mileage.


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I don't find them to be a joke.

Had an LML (they did in those would give the fuel used since last reset)
It was always with in a tiny amount (sometimes over sometimes under) of the reading from the pump.

My L5P was an '18. DIC in it would indicate about 0.5 - 0.6 mpg better than hand calc. It was consistent enough that it could still be used to compare economy at different speeds, weather, trailers etc.

My LM2 hand calcs show it is getting better mileage that the tripmeter indicates.
I check it against the hand calc every fill and record both numbers.

 

[McSpeed]

My 2021 with 9,000 miles delivers:

around town 11-13 pulling 4k lbs enclosed trailer
Hwy steady 70 mph unloaded 19-20
Hwy steady 80 mph unloaded 16-17

Stock with fiberglass cap

Around town it’s about the same as my 2014 5.0 F150. On the hwy, the Duramax delivers about 30% better fuel economy…….at higher speeds it approached 40%.

For the power, comfort and capabilities, my expectations have been exceeded.

It operates in all conditions with much less effort than the F150 (which is a good truck).


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[dscarter27]

New 2021 Duramax AT4 6.6L L5P with 1200 total miles. I am new to the forum but I have read many of your discussions. My truck is currently getting an average of 11-12 MPG. Most of the drives are short in-town trips but there are some highway driving, but when I look at instant MPG it only shows 15-16 MPG when at cruise. I am sure there is a break-in period but have you guys seen a dramatic increase in MPG after break-in and how many miles does it usually take for that to happen? The truck runs great with no problems other than the MPG's. I am just looking for some advice.

Thanks in advance

Jeff

I experienced absolutely the same issue.

I sold my 2015 which would easily get 15 around town and 20 MPH on the highway.

Picked up a 2021 with 70 miles on the odometer. No matter what I couldn't get more than 12 MPG on the highway. I spoke to a diesel tech and he said you need to get at least 3-5 K on the engine before he mileage comes up. Once I hit 3500 K it started to increase and then once I hit 5K I was able to get near 20 MPG on the highway.

One thing I've come to realize is this truck has a very light pedal (very sensitive to driving style). So it's really easy to burn extra fuel when you don't need it. I've found it helpful to to display the instant fuel economy which helps me keep my foot of the floor.

 

[Rguerra]

I have a 2020 Z71 3500 Single rear wheel, stock completely.
I just changed the oil today with 7100 miles and the average over those miles was 19.7mpg.
Towing my trailer last week into the mountains for hunting Average was 13.5mpg
Driving to Corvallis OR from Beaverton OR on I5 I average 23mpg. 70-75mph
Most of the miles on my truck are Highway miles and very little city driving. 19000 miles so far.
Usually get 20-23 on the highway and 17-18 in town.

 

[Elchilero53]

I have a 2022 Silverado 2500HD with 1719 miles. I'm averaging between 17 and 18 mpg with combination freeway and city stop-and-go driving. This based on calculations from weekly fill ups and mileage records. I use a light foot. That truck will take off on you if you don't pay attention; the next thing you know you ! This is about what I was getting with my old 2017 Silverado 1500 LTZ 6.2L on Premium gas under the same circumstances. The best I have gotten is just under 20 mpg freeway driving. Engine is still settling in.

 

[GAM21]

Purchased my truck with 19k and the Trip 2 had never been reset and it it was on 18mpg. I now have 30k and trip 2 is down to 15.8. I don’t think the first owner ever pulled with it. Of my 11k miles owning it I have drove all
Over AK camping and then from AK to AZ pulling the sample camper. Our trip from AK to AS my avg was 10.8.

My best hand calculated was 20.5.

I too have found the the gauge in the truck is far from accurate. I track all fill-ups using Fuelly and I find the gauge is 1.5-2.5 mpg better than hand calculated.

 

[BabyD21]

So just for fun I did a little road trip comparison. 429 miles one way from southern New Jersey to grand island New York. I ran an average speed of 73mph. Up hills down hills, ran cruise control as much as possible. My truck is a 2021 crew cab standard bed, z71 with 15000 miles on it. Only thing I changed on the truck was I blocked off the intake resonator, wrapped the intercooler pips with head wrap and I poured two 8ounce bottles of opti lube XPD fuel additive. Going by their recommendations of 8 ounces to 20 gallons, I know it’s not a 40 gallon tank but I figured that little extra won’t hurt. A ton of people say that it will harm the truck and it will make the truck run more regen cycles. When I drive 1 mile down the road to fill up on fuel and DEF fluid. I will report back the mileage and how much DEF it burned. On my ride home I won’t put any fuel additive in and will compare the results. I run only the Valvoline DEF fluid for less variables in the test. I left NJ at 1pm today and got to grand island NY at 740. I will be leaving the hotel at the same time to help keep the temperature and traffic the same. Hopefully 🙏🏻

 

[Descartian]

I figured I’d chime in. Bought my truck, 2022, Silverado 2500hd high country z71 completely stock, with 18,500 miles on it. I’ve put about 2k miles in the last 3 weeks.

2 weeks ago I did a round trip from Houston to San Antonio unloaded. Mostly flat terrain and I had my cruise control set to 85mph for at least 80% of the trip. Over 400 miles and just under 18mpg.

 

[Melonhead1102]

I figured I’d chime in. Bought my truck, 2022, Silverado 2500hd high country z71 completely stock, with 18,500 miles on it. I’ve put about 2k miles in the last 3 weeks.

2 weeks ago I did a round trip from Houston to San Antonio unloaded. Mostly flat terrain and I had my cruise control set to 85mph for at least 80% of the trip. Over 400 miles and just under 18mpg.

View attachment 1096748

Did you happen to do a hand calculation alongside this? The guys with newer trucks are saying the DIC calculated fuel economy is finally getting closer to the hand calculated. I'm curious what your observations are.

My 2017 is off around 1mpg consistently. The lower my actual economy is, the closer the DIC and hand calc are, which is interesting to me.

 

[Ron Nielson]

I've ask this question many times, no rational answer. Why would hand calculating mileage make a difference? There are only 2 variables to consider: Miles and gallons. Which one, or both, are incorrect in the truck's calculation?

 

[Hoser]

I've ask this question many times, no rational answer. Why would hand calculating mileage make a difference? There are only 2 variables to consider: Miles and gallons. Which one, or both, are incorrect in the truck's calculation?

What are you asking? Are you asking why people want to know the hand calculated MPG vs DIC MPG? If that’s the case, it’s because the DIC is wildly inaccurate, contrary to what @Melonhead1102 says above. My truck is always optimistic, sometimes up to 1.5 mpg, so yes, hand calc vs DIC there is a big difference. That’s why guys ask what the hand calc mpg is. As far as which on is incorrect in the truck, the gallons is incorrect.

 

[Hoser]

My lifetime MPG is 10.7, and yes, hand calculated.

 

[smeezy]

If you use a calculator is it still considered hand calculated?

 

[Hoser]

If you use a calculator is it still considered hand calculated?

You push the buttons with your fingers right?? 😂

 

[Melonhead1102]

I've ask this question many times, no rational answer. Why would hand calculating mileage make a difference? There are only 2 variables to consider: Miles and gallons. Which one, or both, are incorrect in the truck's calculation?

If there are only 2 variables, as you have said, then why on earth would there be a difference between miles driven divided by gallons pumped and the economy reported on the DIC?

The DIC vs Hand Calculated is not the same.

 

[Melonhead1102]

...it’s because the DIC is wildly inaccurate, contrary to what @Melonhead1102 says above.

I'm just looking to see how inaccurate the newer trucks are compared to my 2008 LMM and now my 2017 L5P. My LMM was off by usually 2mpg, and my L5P is almost exactly 1 mpg off.

So if that's you're definition of "wildly inaccurate", then so be it. I just reported what I have recorded with my trucks and didn't put a personal opinion on whether I consider that accurate enough or not. The numbers are what they are.

 

[BoiseRob]

One thing that you may need to take into account is larger than stock tires. The distance traveled will be measured differently by the truck. Proof is to verify this with the Speedometer Test on the interstate. A larger tire will roll 1 mile on the odometer beyond/past the verified mile on the Interstate...

 

[Hoser]

I'm just looking to see how inaccurate the newer trucks are compared to my 2008 LMM and now my 2017 L5P. My LMM was off by usually 2mpg, and my L5P is almost exactly 1 mpg off.

So if that's you're definition of "wildly inaccurate", then so be it. I just reported what I have recorded with my trucks and didn't put a personal opinion on whether I consider that accurate enough or not. The numbers are what they are.

Dude, I’m not attacking you or implying you are wrong or dumb. I’m just stating facts based on actual real life personal data and experience. Isn’t that what a forum is for???? Correcting something doesn’t imply a threat or any or any other negative connotations. You heard something, and I’m just clearing things up with facts. My truck is more inaccurate than any previous trucks. Is there a problem with putting a personal opinion on how I feel about the accuracy? For me, 1.5 mpg off is close to 20% off, and sometimes up to 25%. That to me is significant, or, as stated previously, wildly inaccurate.

 

[Hoser]

One thing that you may need to take into account is larger than stock tires. The distance traveled will be measured differently by the truck. Proof is to verify this with the Speedometer Test on the interstate. A larger tire will roll 1 mile on the odometer beyond/past the verified mile on the Interstate...

This is very true. And it’s a percentage. Many guys will say their speedo is off 5 mph, or 3 or 10. But thats not a constant, the percentage is. So using the test as mentioned or a GPS you can figure out the percentage that your Speedo is off if you have larger diameter tires. Then divide miles driven by gallons used then multiply by the percentage the Speedo is off and That will give you accurate MPG.