Well considering your tire size jumped by almost 14% and I'm guessing you didn't fix the speedo, your mileage is more like 16.

I'm going to agree with the 02 sensor, since it was such a sudden drop. It may need a tune up too. You should still be able to get almost 20 out of that truck though. Regearing would help too.

90 pickup, 22RE, stiff-ass Ranchos, 2.25 catback, 4:1 header, conical intake, 15x7 ICW alloys, 32x11.50 Dunlop Mud Rovers, 4.56s w/v6 rear

-Farm truck until school is done...then plans

2000 Honda CRV EX 5 speed

-Driver