Abrupt fuel mileage drop

[Ditchplains1]

Here's a puzzle that I figured out.....
Recently mounted new **** Cepek Fun Country tires 315's with rubber bead balancing, and had my alignment done CORRECTLY!!!!, as well as changed my brake pads.
Suddenly my mileage plummeted; averaging close to 16 mpg, it dropped to 13.
Brakes NOT dragging. No pulling to either side. Coasts like hot ice skates on ice.
Not burning oil; last oil change 3,000 miles prior to onset of decreased mileage...Mobil 1 synthetic as always and new Bosch filter. Air filter looks clean. No emergency brake drag. No abnormal sounds at idle.
The only difference I can be certain of was a new hum with the new tires...

OK....What was it?
Yes I figured it out, and no it was nothing exotic....
Answer tomorrow......

Eddie

 

[Ditchplains1]

No one curious?

 

[EricM]

Tire pressure.

 

[Ditchplains1]

EricM,
Good thought...should have mentioned it in earlier post. All four tires at 50# after installation. I dropped them to 42# and kept them there. Same pressure as previous BFG's.
But no not the answer....

Eddie

 

[brc misfit]

went with a larger tire, decreasing mileage. or the neighbor kid is siphoning off gas while your sleeping.

 

[Truckzor]

I was going to guess that the tires were directional and installed backwards but I don't think the fun country is directional. Hmm...

 

[badm0t0rfinger]

Weight bro. I went from BFGs to X3s on beadlocks and went from right around 14.2 to just about 12.5. My commute also changed, but I think that less of a role

 

[Ruger]

Stay tuned for the next preposterously delayed episode of Mystery Automotive Theater!

 

[Hockster]

3 mpg loss is quite high for just a same size tire swap but it could be. I installed BFG KM2's and only lost 1.5mpg's. Switched to the new BFG and went back to where it was.

 

[crash457]

I'll guess a loose plug wire.