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Looking for better MPG

jorswift
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jorswift Enthusiast

jorswift

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Have a 2015 sierra 1500 5.3. Bought truck several years ago with 70k miles. Now with having to return back to office, I am over 100k. Truck is mainly stock, but have some 33" tires and leveling kit. With having to drive a ton more now and filling up more often, I am looking to do somethings to get better MPG. Truck seemed to get good mileage when I first bought it around the 70k mark.Any advice? Thanks.

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Silverado4x4 Senior Enthusiast

Silverado4x4

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37 minutes ago, jorswift said:

Have a 2015 sierra 1500 5.3. Bought truck several years ago with 70k miles. Now with having to return back to office, I am over 100k. Truck is mainly stock, but have some 33" tires and leveling kit. With having to drive a ton more now and filling up more often, I am looking to do somethings to get better MPG. Truck seemed to get good mileage when I first bought it around the 70k mark.Any advice? Thanks.

Get rid of the 33s and go back to stock size and remove the leveling kit. The leveling kit raises the front and creates more wind drag and the 33s are heavier than the stock tires which take more power to keep them rolling, rolling resistance. 

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scrapen Enthusiast

scrapen

Posted
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With stock tire size expect around maybe 18 mpg.  So if you average 16-17 I’d say it’s normal.  If you haven’t done plugs there’s a good chance they’ve never been done.

 

personally if you’re putting on a lot of miles a beater car can pay itself off.  My diesel vw is averaging 49 mpg (.08 per mile last 8 years vs .19 per mile on my truck (tuned for 91)). I’ve kept over 50k miles off the truck which now sits at 42k.

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jorswift Enthusiast

jorswift

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Yeah, not looking to see "great" results. Just something a little better I guess. I know the level and tires would kill it, but at that time I was not driving that much. Thinking of a tuner to calibrate tires and get the 87 tune.

mikeyk101 Senior Enthusiast

mikeyk101

Posted
Posted

Another thing that may be affecting your gas mileage is regarding the 33" tires. Just curious if you corrected your speedometer? I'm not 100% sure but believe the speedometer is probably linked with the odometer. With larger sized tires, if speedo not corrected, it will show you are going slower than you are. So that would translate into showing you are covering less ground than you are. So if you are covering less ground but still using the same amount of fuel, it will obviously look like you are getting less mpg than you really are. 

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newdude Senior Enthusiast

newdude

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Are they 33" aggressive tires?  Or 33" highway tread?  Are they flotation size so like 33x12.5x20?  

 

Going up in diameter, sure you'll see MPG change but the weight and tread design and if its a tire size like I mentioned has much more effect here than them being 33" diameter.  

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diyer2 Senior Enthusiast

diyer2

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Stock size tires, remove lift. Best mileage you'll get.

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Z45 Senior Enthusiast

Z45

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Posted (edited)
On 8/14/2025 at 10:25 AM, jorswift said:

 Thinking of a tuner to calibrate tires and get the 87 tune.

More $ wasted chasing a dream.   You are still pushing 2.5 tons of steel down the road.  Put the truck back to 100% stock if you really want to keep it, but spending money to get better mileage is a pipe dream.  Spend 100's to save pennies.  

Edited by Z45
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Grumpy Bear Senior Enthusiast

Grumpy Bear

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Posted
On 8/14/2025 at 6:31 AM, jorswift said:

Have a 2015 sierra 1500 5.3. Bought truck several years ago with 70k miles. Now with having to return back to office, I am over 100k. Truck is mainly stock, but have some 33" tires and leveling kit. With having to drive a ton more now and filling up more often, I am looking to do somethings to get better MPG. Truck seemed to get good mileage when I first bought it around the 70k mark.Any advice? Thanks.

 

1.) Lower and stock size H/T tires. Already said. Goes to frontal area and rolling resistance. Oh and run those tires hard. Adding 3 psi over nameplate will not kill the tire nor the wear if the alignment is correct. 

2.) Alignment. Tires standing up near zero camber but negative, -.2 to 0 and even. Toe positive, even and minimum, .02-.04. Shoot for zero steer-ahead and zero thrust angle. And take some caster out of it but stay in spec. 

3.) Tune up and not a tune. Standard stuff. Plugs, wires air filter. PVC system. 

4.) Minimum weight. That stuff in the bed/cab you don't use, ditch it.

5.) Soft tonneau cover and keep the gate up. 

6.) You'll love this one...Slow down. Drive like you haven't any brakes. It's an art. Anticipate lights and traffic. Yea, it takes a few more minutes so start earlier. I'm not talking snails pace but even 10 mph make a HUGE impact. At least the speed limit. Get used to being passed but not a a$$. 

7.) Scan Gauge III. You'll be surprised how much instant real time feed back corrects bad habits. Hones point #6. 

8.) Stay out of the drive through. 

9.) Pan heater in the winter. Cold oil is the big end of the winter fuel economy loss. On trips as long as yours 0W* oil gives you next to nothing over 5W* and use a 'slick oil' Lubricity is huge. And not all 0W or 5W oils are created equal. The cold weather properties of the specs are MAXIUMS not minimums and those that use PAO's instead of Group III at the bulk base will always have lower CCS numbers. I'll let you fret the brand. 

 

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JimCost2014 Senior Enthusiast

JimCost2014

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Posted

Not to be a complete smart-ass, but park it in the garage and get a small commuter car. A V-8 truck is only going to get a certain MPG, no matter what you do. If you believe the stories of 30++ mpg members are getting, you are going to be disappointed with your results.

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Grumpy Bear Senior Enthusiast

Grumpy Bear

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12 hours ago, JimCost2014 said:

Not to be a complete smart-ass, but park it in the garage and get a small commuter car. A V-8 truck is only going to get a certain MPG, no matter what you do. If you believe the stories of 30++ mpg members are getting, you are going to be disappointed with your results.

 

One has little to do with the other. That said and in a more liberal meaning; it is wise to compare only to yourself. Perhaps that was the intent.

 

If you think you can't get a 15-20% improvement, you'd be mistaken. Go all in and 30% is not off the table. Pepper is not a "Story", the results were the results hand calculated and graphed. Everyone got to follow along in 2019 were for the year it tapped 30+ mpg. The items on the list I put up were the ones I used to get that result. In print in my build thread. 

 

Can I do that with a four door V8? 30 mpg? No. But I can get one to respond to the physics involved as can anyone else that honestly tries and applies the science.

 

As for the other suggestion. Yes. And if you won't believe 30+ with a pickup you will never get your head around 52+ mpg in a Mitsubishi Mirage for it's first year.

 

30,173 miles in year one using 578.75 gallons of fuel = 52.13 mpg RESULT. 718 engine hours = 42 MPH RESULT

13 mpg over the EPA combine value. 33% improvement! 6 mph faster than that national average. Rinse and repeat or Pepper using exactly the same methods to get exactly the same results. Quite a story. 

 

EPA numbers: The Mitsubishi Mirage has an EPA fuel economy rating of up to 36 miles per gallon in the city and 43 miles per gallon on the highway, averaging around 39 miles per gallon combined. 

 

 

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asilverblazer Senior Enthusiast

asilverblazer

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I was never able to get a commuter car to pencil out. 

 

Starting at a modest 5000.00 for the car price, plus its own maintenance, registration, insurance and gas. Never even comes close to saving me money. 

 

Going up on the 5000.00 so that I'm not spending my commute in an absolute $hitbox only makes it worse. 

 

MY math, assuming I ONLY drive the commuter and don't drive my truck AT ALL, with some simple rounding... 

18000 mile per year in the truck averaging 17 mpg = 1050 gallons of diesel at $3.10 per gallon = $3300.00 per year.

In a car that gets 30 mpg = 600 gallons of gas at $2.75 = $1650.00 per year. 

I would be saving about $1650.00 in fuel costs.

From that savings I have to buy the car and pay the above continual expenses. $150.00 in oil changes, $100.00 in registration, $600.00 in insurance, assume no other repairs are needed (unlikely given we're trying to save money on the car) leaves $800.00 per year in savings. If I buy the car at the above $5000.00 price it would take over 6 years to realize any savings, at which point, the car will need tires and other maintenance costs that would likely push the savings point out to over 7 years. 

 

Raising the purchase price to lower the maintenance cost or lowering the purchase price would raise the maintenance amount... never going to work for me. 

 

OP's 30k miles in "several years" doesn't sound like an amount of miles that would push this equation to a point that make sense for him either. 

 

In broader terms this is why truck owners DO CARE about mpg, so many say "you bought a truck it won't get good gas mileage... you should have bought a car..." don't understand that some people drive to a job Monday through Friday and have other responsibilities or activities that require a truck on the weekend. Having two separate vehicles for this doesn't make sense based on the dollars above. 

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swathdiver Senior Enthusiast

swathdiver

Posted
Posted
On 8/14/2025 at 7:31 AM, jorswift said:

Have a 2015 sierra 1500 5.3. Bought truck several years ago with 70k miles. Now with having to return back to office, I am over 100k. Truck is mainly stock, but have some 33" tires and leveling kit. With having to drive a ton more now and filling up more often, I am looking to do somethings to get better MPG. Truck seemed to get good mileage when I first bought it around the 70k mark.Any advice? Thanks.

 

Keep up with the maintenance and slow down.  That's all you can really do without spending money.  

 

Big truck = safety

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