Thread: Help! Gas Mileage Dropping

Howdy. My Super 3.8L motor blew at 84K even tho I drove it gently. Go figure. I replaced it with a 46K engine (same type)...started it up, all computers came on line and checked out. We replaced EVERYTHING replaceable when we did the swap - plugs, wires, pumps, filters, etc. Smooth as silk from the day of the install. The motor seems to run fine, no codes, smooth, etc. My gas mileage had dropped from close to 21 all around with the old motor, to 17 with this one. Embarrassed to say that I don't know if this happened recently or since the motor was replaced 20K ago.
ANYONE help me out? What are your thoughts about the diff in mileage? - oh, and replaced the plugs, wires, and fuel pump again just for good measure.

Thanks a ton!
Brent

What type of spark plugs did you use? Using 91+ octane I hope? Cat clogging up?

A faulty, or out of range ECT sensor (engine coolant temerature) will hurt your fuel milage. You state in your post you changed everything, but did not state anything about the sensors. It would be a good idea to check and make sure it is working properly, even thou you your not getting a DTC for it.