Sudden Drop in Gas Mileage

[Revchuck38]

I've got a 2020 1500 Classic with the V6 with about 74k miles on it. It usually gets ~22-23 mpg on the highway and 18-20 mpg around and to and from town. On my last road trip, it only got 18 mpg. Prior to that trip, I replaced the air filter with the appropriate Fram filter, it replaced the same model Fram that was in it.

I know that plug replacement is called for at 100k miles and that lots of folks have gone well past that with no reduction in mileage. Do the plugs sometimes need to be replaced sooner?

If it might be something else, what should I check?

Most of the miles are highway with the cruise set for 70-75 mph, and I'm fairly gentle with it around town.

Thanks!

 

[crash68]

Has the ambient temperature been colder than usual? Any change if the fuel? Wonder if it's possible you filled up with a tank of winter blended fuel.
I'd run a few tanks worth before going off of MPG to determine if there's a problem with the truck. Too many variables can swing the fuel economy to use MPG as a diagnostic number from just one tank.

 

[Dean2]

Crash is spot in, fuel, temp, minor headwind and a ton of other things can swing mileage that much easily.

 

[SitKneelBend]

I've got a 2020 1500 Classic with the V6 with about 74k miles on it. It usually gets ~22-23 mpg on the highway and 18-20 mpg around and to and from town. On my last road trip, it only got 18 mpg. Prior to that trip, I replaced the air filter with the appropriate Fram filter, it replaced the same model Fram that was in it.

I know that plug replacement is called for at 100k miles and that lots of folks have gone well past that with no reduction in mileage. Do the plugs sometimes need to be replaced sooner?

If it might be something else, what should I check?

Most of the miles are highway with the cruise set for 70-75 mph, and I'm fairly gentle with it around town.

Thanks!

I'll pile on and say besides winter fuel, check to see if your parking brake cable is sagging. If it is, it is dragging on the rear wheels.

 

[Revchuck38]

Thanks, guys! I recently did another trip and averaged 23 mpg. The trip that started me thinking was pretty windy, so that was probably the culprit.