I need help on this problem I'm havin with a rebuilt motor. Runs great, idles smooth, timing is right, but I'm getting about 7.0 MPG now when it used to be around 12 with the old motor.
Could the speedometer cable going bad be responsible for the difference or is the odometer accurate even if the speedometer is flucuating wildly when I'm driving.
I'm going to change the O2 sensor, plugs and wires, but I can't afford to drive around at 7.0 MPG

 

your new engine is probably "tight"
requiring more horsepower to turn.

it should gradually get better on it's own

 

what engine anyways?

 

If the speedometer is wrong, the miles driven will be wrong too. You need an accurate measurement of how far you've driven in order to calculate MPG.

 

Like JLDickmon said.....Usually with new vehicles, the MPG gets better as the engine breaks in....so being your motor is "tight", it may get better as time passes.