Poor fuel mileage after new tires, a flowmaster 40 series exhaust, and a k&n air fliter?

[Nels]

My experience with my 5.7 hemi was: larger, heavier, more aggressive tires lost 2-3 mpg. Rplaced stock muffler with Flowmaster Flow FX gained back about 1 mpg. Averaging around 17 mpg, although declining recently I believe from switching to winter blend fuels. I have not recalibrated the speedo, but I calculate mpg myself, with an adjuster for tire size.

 

[dog___fighter]

I have a 2021 ram 1500 with the 3.6 pentastar V6 E-Torque. I put new tires on which originals were 275-65-R18
I put on 285-65-R18, a new flowmaster 40 series, and a k&n air filter( not cold air intake and cone) and my mileage is like 17.6 now from around 25. Can anyone give me some pointers on If this is causing it or what else I should maybe look into. No warranty anymore so trying to figure it out before paying dealer prices for diagnostics and such.

I have a 3.5” lift with 20x12 in 35x12.50 with a muffler delete and AFE intake and get around 14 mpg

 

[ferraiolo1]

Why aren’t you talking about the actual tire you put on or the pressures you’re running?


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Op where did you go?


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[Rick3478]

Looking at a slightly different angle, lower restriction intake and exhaust make it possible to burn fuel at a higher rate. At its most basic, that's how you make power, right?

Also, you may have lowered the temperature of both incoming air and outgoing exhaust, and the ECU will trim fuel to compensate.