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i had my 2016 Ram 1500 3.6 litre pentastar leveled and replaced the tires with 285/70/17 and have a k&n cold air kit on the truck. Since I replaced the tires my gas mileage has gone from 23 mpg to 12 mpg. Any ideaas what is causing this decrease in mileage?
 

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11 MPG from a level?? Something's not right
 

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Too much oil sprayed on the K&N filter ???
 

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try putting stock filter back in, instead. then only change is the level and tires. might see 2mpg from the level. another 10-2mpg from teh tires bu that should be max.
 

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Are the tires the same size as your old ones? My truck had 35/12/20s on it when I bought it and my mileage was 10-11 mpg I had the computer programmed for my tires and it improved now I get 14-15 around town and 19-22 hwy depending on how I drive. Also I increased my tire pressure I was running 45 psi now I’m at 55 tires go up to 80psi for heavy loads. I running nitto exo awt tires and I love them!
 

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I would suggest that you fill the tank with gas & hand calculate the mileage with the current K&N
Then fill the tank again & hand calculate MPG while running a new dry filter

don't make any other changes while the above MPG check is being done
 

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I noticed that my mpg was off with the bigger tires but also the shift points we off too. Everything is running off the computer so with the wrong tire size the computer thinks the truck is going slower or faster and shifts according
 

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As mentioned do a hand calculation for the MPG, My question about your tires did you go from a 4 ply to a 10 ply tire ? The weight of a 10 Ply will kill mpg about 2 to 5 mpg, Just a thought
 

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If your tires are bigger than the ones you took off, your mileage will go down even if hand calculated! The odometer will be off. You can go to a known e-retailer like tire rack and get the runout of each tire. Divide the old tire's runout length by the new tires runout length and multiply that ratio to your odometer reading to get mileage. Then you can calculate miles per gallon.
 
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