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Fuel Mileage Drop - Is this amount normal?

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PMad Enthusiast

PMad

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So not too long ago, i got my 2017 Silverado 1500 Double Cab leveled with a 2 inch tough country leveling kit. I then added a tonneau cover and switched from Auto to 2 wheel drive mode and was averaging 18.5 to 18.8 mpg. Before the leveling kit, tonneau cover, and 2wheel drive, I averaged 16.4 to 16.7 on 20 inch stock wheels, tires measured at 31 inches.

 

After about a month I upgraded to 33X12.5X20 toyo open country R/T's and now my MPG has dropped to 14.9 to 15.2mpg. 

 

I'm feeling like this drop is a bit larger than what it should have been? I expected a drop but i thought i'd probably get closer to my original 16.4-16.7 stock average.

 

The tires are at 37psi, but in the mornings they are at 34 which is when half my usual driving is done, then during the day its up at 37. Sometimes i'll see a tire or two go up to 38-39.  I'm wondering if this is the issue? Do i need to up my PSI? 

IMG_20180623_210803.jpg

Sierra706 Senior Enthusiast

Sierra706

Posted
Posted
So not too long ago, i got my 2017 Silverado 1500 Double Cab leveled with a 2 inch tough country leveling kit. I then added a tonneau cover and switched from Auto to 2 wheel drive mode and was averaging 18.5 to 18.8 mpg. Before the leveling kit, tonneau cover, and 2wheel drive, I averaged 16.4 to 16.7 on 20 inch stock wheels, tires measured at 31 inches.
 
After about a month I upgraded to 33X12.5X20 toyo open country R/T's and now my MPG has dropped to 14.9 to 15.2mpg. 
 
I'm feeling like this drop is a bit larger than what it should have been? I expected a drop but i thought i'd probably get closer to my original 16.4-16.7 stock average.
 
The tires are at 37psi, but in the mornings they are at 34 which is when half my usual driving is done, then during the day its up at 37. Sometimes i'll see a tire or two go up to 38-39.  I'm wondering if this is the issue? Do i need to up my PSI? 
IMG_20180623_210803.thumb.jpg.95edbe8abe498dbb09e2aec451e723ed.jpg


Larger tire changes the ratio and effects your speedometer and odometer. Aggressive tread pattern and tire weight are also to blame


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PMad Enthusiast

PMad

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2 minutes ago, Bushleaguechew said:

 


Larger tire changes the ratio and effects your speedometer and odometer. Aggressive tread pattern and tire weight are also to blame


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I totally get that, and i expected a drop, but this is nearly 4mpg. I've seen trucks starting off with even smaller tires then i have go up to 33's and only lose 2 to 2.5mpg, i lost almost 4 and i went from 31's to 33's. It seems too steep, and i can only think of the tire psi possibly being the blame with half my driving being done in the mornings with the PSI at 34 when they should be 37.

wforrest08 Senior Enthusiast

wforrest08

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Are hand calculating your MPGs or just relying on the computer to be right? 

 

Did you recalibrate the speedo?

 

The weight of the wheel/tire combo, amount of plies, and tread design all play a part in MPGs (rolling mass). 

TXGREEK Senior Enthusiast

TXGREEK

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I totally get that, and i expected a drop, but this is nearly 4mpg. I've seen trucks starting off with even smaller tires then i have go up to 33's and only lose 2 to 2.5mpg, i lost almost 4 and i went from 31's to 33's. It seems too steep, and i can only think of the tire psi possibly being the blame with half my driving being done in the mornings with the PSI at 34 when they should be 37.


Level kits raise the front allowing more air to confront your front end creating resistance as well as bigger meatier tires. Realize you have a level in front but is your rear end lifted at all??


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Sierra706 Senior Enthusiast

Sierra706

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Posted
I totally get that, and i expected a drop, but this is nearly 4mpg. I've seen trucks starting off with even smaller tires then i have go up to 33's and only lose 2 to 2.5mpg, i lost almost 4 and i went from 31's to 33's. It seems too steep, and i can only think of the tire psi possibly being the blame with half my driving being done in the mornings with the PSI at 34 when they should be 37.


You lost 2-2.5 and also your uncalibrated speedo, odometer and trip computer are showing a further 1.5-2 loss that isn’t real and will go away once your properly calibrated.


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PMad Enthusiast

PMad

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Oh! I forgot about speedometer!

 

I havent had it recalibrated. 

 

The back end was never touched, only the front went up 2 inches so i still have an 0.5 inch rake that is damn near unnoticeable. I measure my mpg by the tank, when i fill up, i reset the trip meter. In the last 1/2 tank, the average is pretty much set, it may go up or down 0.2 before 1/4 tank when i fill it back up, but thats typically when i take my reading for that tank of gas.

 

Thanks for the replies!

TXGREEK Senior Enthusiast

TXGREEK

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Oh! I forgot about speedometer!

 

I havent had it recalibrated. 

 

The back end was never touched, only the front went up 2 inches so i still have an 0.5 inch rake that is damn near unnoticeable. I measure my mpg by the tank, when i fill up, i reset the trip meter. In the last 1/2 tank, the average is pretty much set, it may go up or down 0.2 before 1/4 tank when i fill it back up, but thats typically when i take my reading for that tank of gas.

 

Thanks for the replies!

 

When you’re on the highway your truck doesn’t sit level, it’s raising in front from wind while dropping in the back, add 1” in rear may help. I’ve got 18 CC 6.2 Z71 2” front and added 1” rear, 20X9 33” KO2’s with Fuel wheels. Highway average 22-23 city average 15-16. I’ve got the RollNLock bed cover too.

 

 

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PMad Enthusiast

PMad

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17 minutes ago, TXGREEK said:

 

When you’re on the highway your truck doesn’t sit level, it’s raising in front from wind while dropping in the back, add 1” in rear may help. I’ve got 18 CC 6.2 Z71 2” front and added 1” rear, 20X9 33” KO2’s with Fuel wheels. Highway average 22-23 city average 15-16. I’ve got the RollNLock bed cover too.

 

 

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Thanks for that! That info helps too. I'm using Fuel Assault 20x9's with 33" Toyo Open Country R/T's. I dont have the rollnlock but i'd love one haha, i have a cheaper tri-fold, but it works very well for what i need. I'm not sure of my city vs hwy averages, but my overall averages are what i listed. Maybe i should measure those averages too? That might help with some info. 

 

Did you get your speedometer calibrated? You mentioned adding 1" in the rear, how noticable is your rake with that? My goal was to get rid of my rake.

TXGREEK Senior Enthusiast

TXGREEK

Posted
Posted
Thanks for that! That info helps too. I'm using Fuel Assault 20x9's with 33" Toyo Open Country R/T's. I dont have the rollnlock but i'd love one haha, i have a cheaper tri-fold, but it works very well for what i need. I'm not sure of my city vs hwy averages, but my overall averages are what i listed. Maybe i should measure those averages too? That might help with some info. 
 
Did you get your speedometer calibrated? You mentioned adding 1" in the rear, how noticable is your rake with that? My goal was to get rid of my rake.

No I did not, no need, I just add a few extra on lol.


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TXGREEK Senior Enthusiast

TXGREEK

Posted
Posted
Thanks for that! That info helps too. I'm using Fuel Assault 20x9's with 33" Toyo Open Country R/T's. I dont have the rollnlock but i'd love one haha, i have a cheaper tri-fold, but it works very well for what i need. I'm not sure of my city vs hwy averages, but my overall averages are what i listed. Maybe i should measure those averages too? That might help with some info. 
 
Did you get your speedometer calibrated? You mentioned adding 1" in the rear, how noticable is your rake with that? My goal was to get rid of my rake.


Just having a hard bed cover helps


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