Averaged 12mpg on road trip, expected better

FirstAscent · January 3, 2020

Recently finished up a mountain bike road trip from Oregon to California and back, I always track my mileage and was hoping to see an increase with all hwy miles. Pretty much every tank I averaged 11-12mpg. Wasn’t towing anything either.

I know it’s not a Prius, yes I realize I have it lifted with 35’s, but still was expecting more than 12.

I have the 5.3, makes me reconsider if I made the right choice. No I’m not gonna sell it, I really love the truck! Just wish I could get better omg on a lifted truck, is that too much to ask for hahaha

I hear “stories” of people towing and getting better mpg, granted they are typically diesel

spizike9 · January 3, 2020

Lifted on 35s with the 5.3 and you thought you’d get better mileage than that.

Londart2020 · January 3, 2020

23 minutes ago, FirstAscent said:

Recently finished up a mountain bike road trip from Oregon to California and back, I always track my mileage and was hoping to see an increase with all hwy miles. Pretty much every tank I averaged 11-12mpg. Wasn’t towing anything either.

I know it’s not a Prius, yes I realize I have it lifted with 35’s, but still was expecting more than 12.

I have the 5.3, makes me reconsider if I made the right choice. No I’m not gonna sell it, I really love the truck! Just wish I could get better omg on a lifted truck, is that too much to ask for hahaha

I hear “stories” of people towing and getting better mpg, granted they are typically diesel

I have the 6.2l no lift factory tires, but mostly city around town driving and I get 15.8. So either with the bigger tires you speedo is off and that's not accurate or you are into the throttle way too much..

CamGTP · January 3, 2020

How fast were you going though?

Even a lifted truck with 35's should get 15-17 on a open road doing 65-70mph.

FirstAscent · January 3, 2020

How fast were you going though?

Even a lifted truck with 35's should get 15-17 on a open road doing 65-70mph.

Probably 70 and on cruise control the majority of the time too. Yeah if it were 15, I’d expect at least that. I think the best I got was about 12.3.

Thomcat · January 3, 2020

Was the speedometer recalibrated for the larger circumference tires and tires appropriate for the stock rear axle ratio? Changes in drive line angle may also have a small effect increasing drivetrain resistance.

The RST comes stock with 18" tires and a 3:42 rear. When you order the larger the dealer installed 22"s as an option the RST comes with a 3:23 rear and steel transport wheels. Dealer installation includes mounting and balancing the 22"s and recalibrating the speedometer for the larger tires to maintain speedometer/odometer/tranny shift point (and obviously cruise control) accuracy. To verify I have checked odometer accuracy against highway mile markers and speedometer against radar speed warning displays located on certain roads - both were dead on.

From what I was told by the dealer they can/will only recalibrate for tire sizes and rear end gear ratios that are factory for the truck.

Z45 · January 3, 2020

At 70 mph your mpg will take a hit especially with the truck lifted. I notices the MPG on my truck drops about 1mpg from 60 to 70.

Quote

I hear “stories” of people towing and getting better mpg, granted they are typically diesel

That's just it, Stories! Take that with a grain of salt. Some talk about their mileage like fishermen talk about their catch. IMO you are lucky to get what you are getting with the truck modified. If you want better mileage, get rid of all the things you done to make it worse. PS-Been driving a 4wd truck for 40 yrs.

blckblt · January 3, 2020

Did you get the speedometer recalibrated?

6" inch lift with 35" inch tires on 22" inch rim. You added a lot of wind resistance/aerodynamic loss etc. I would guess that you added some weight to the truck with the lift and tires (those tires weigh 77 pounds each). Those tires are not going to be rolling friendly being an off road/mud type tire.

How old is the truck? Is it broken in?

Did you ever measure MPG before the lift and tires?

Flat highway or hills?

smrr1 · January 3, 2020

A few things in my opinion

1-yes you killed all chances of decent fuel mileage lifting a 5.3 and putting heavy wheels/tires but 12 on a road trip is a little low depending on speed and terrain. Some people, including myself on previous trucks, have seen a loss of 1-2 mpg with just a tire change and no lift.

2-speedometer/odometer calibrated correctly?

3-Did you check mileage by hand or the computer? If by computer did you reset it before the trip? If not your results will be avg’d with all your previous driving.

4-last one if you are still running a 323 gear you will gain power and mileage by changing them to something more aggressive.

Good luck with it!

Donstar · January 3, 2020

8 hours ago, FirstAscent said:

Probably 70 and on cruise control the majority of the time too. Yeah if it were 15, I’d expect at least that. I think the best I got was about 12.3.

Set your cruise to 60 and see the difference. I know you won't want to stay at 60 but you will be surprised as to the difference in mpg's. When pulling my travel trailer, slowing down makes a significant difference at the pump. However, a senior pulling a Winnebago doesn't look unusual going slow. A guy in a lifted truck doing the same would look suspicious

aseibel · January 3, 2020

54 minutes ago, Donstar said:

Set your cruise to 60 and see the difference.

It is a surprising difference. economy is so much better at 60 mph.

Its funny to me how they call the EPA tests "city" and "highway". People expect to see the "highway" numbers on the interstate, but that is far from realistic. They should do a 3rd test loop at a constant 75 mph and list that as "freeway" mileage.

The EPA's highway test is more like a leisurely Sunday drive through the countryside to grandma's house.

Cpl_Punishment · January 3, 2020

Or consider not using cruise control, especially if you're driving in a hilly area. It's much more efficient to maintain a consistent accelerator position, rather than maintaining a set speed.

Osteoman · January 3, 2020

I have an At4 6.2 2019 with the factory 2" lift and get 17-18 on the highway at 70. I got 11-12 when I was hauling my 3600 lb airstream.

I bet, like others have said above, that is not accurate.

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FirstAscent · January 4, 2020

No my speedo hasn't been calibrated to account for the 35's. GPS at that speed had me about 5mph faster. So that would net me slighter better mpg but maybe .3 extra?

I always thought cruise control helped with mpg? so good to know. However, when my girlfriend was driving during the portion of the trip she never uses cruise control and it honestly didn't change much. Looking at my fuel logs during the trip it was anywhere from 11-12.7mpg

All logs were checked manually using pump numbers and odometer miles. There's always potential for errors but after 10+ fill ups and getting the same results, I think it's pretty accurate.

@blckblt It's a new 2019 Silverado so there "shouldn't" be any maintenance issues affecting the mpg. It now has 8k miles so plenty broken in by now.

Next time I get a stretch of open road I'll have to keep it at 60mph and do a mpg test then, now I'm curious to see how much it affects it.

smrr1 · January 4, 2020

Try it with a gps tracking your miles since your speedo/odo is wrong. Then you will have an accurate mpg number. If you hand calculated 12.7 with the wrong miles maybe that is actually 14-14.5. If you were driving 70+ i’d say that is pretty reasonable considering the lift and tires. Also i don't recall if you said any wind on the trip. That will hurt you too. I have had trips that changed 1-2 mpg with my speed and winds. Also winter gas right now could be a factor.

Basically there is a whole slew of reasons why your mpg sucked but first check it with the accurate miles then start analyzing everything else. Just my approach.