afjeep2082 said:
hummm would the motor running pretty hot have anything to do with this then?
How hot is pretty hot? As mentioned around here a zilllion times, 210° is perfectly normal. You can do some serious damage up around 240° - 250°, like blowing head gaskets, warping the head casting, valve damage, on and on. This kind of damage could have a serious impact on gas mileage.
Assuming that's not the case, I'd still guess something to do with engine management.
Under normal running conditions, various sensors provide the computer with information to determine fuel and spark timing parameters. The oxygen sensor reads the results and lets the computer know if the engine is running too rich or too lean on fuel. Based on this info, the computer makes further adjustments, the oxygen sensors checks again and on and on it goes. This process of adjusting and checking repeats over and over iin a continuous loop, many times a second.
Like RichP said, when the engine is cold, the oxygen sensor input is ignored. The computer depends on stored maps to provide fuel and spark timing based on such things as RPM, throttle position, air temp, etc. The results are not checked by the oxygen sensor, so there is no feed-back loop. There are other conditions where the oxygen sensor is ignored, such as wide open throttle or closed throttle (coasting or decelerating).
Without the feedback from the oxygen sensor, the computer settings tend to be on the fuel-rich side which results in poor mileage. Your roof rack with spare tire, lift, larger tires, poor choice of gears and who knows what else will hurt your mileage, but that's the norm around here. Considering this, you might expect anywhere from 12 to 16 MPG. Your's if half that. Somethings not right in the engine compartment.
HTH
