I would think that a faulty/failed coolant temp sensor would trigger a CEL, and a stalling vehicle when at operating temperature. At least that is what happens on the GM vehicles I owned.
The PCV valve is generally common culprit for excessive oil consumption, but I am not sure about gasoline.
Crafty neighbor/co-worker: possibly?
Hole in the fuel line: Would definitly smell it
Definitely check the tire pressure.
Oil companies have over 90 different blends of gasoline that they have to shuffle depending on the seasons of the year and the region of the country (in the U.S., at least for EPA reasons.)I have noticed 2-3 MPG changes because of the blends for the different seasons.
The car could be stuck in the "OPEN LOOP" mode, which would make it run rich all the time. This would NOT necessarily trigger a CEL, either.
Timing: possibly, but that requires a computer reprogram to reset (no distributor anymore.)
The oil viscosity is based on the "pour point" of the base stock and the amount of polymer chains used to increase the viscosity when warmed up. The viscosity index (VI) is such that for a given multiweight oil (i.e. 5w30), the oil will increase its viscosity by literally "uncoiling" the polymer chains at a set temperature. This temperature is a fixed value and is controlled/determined by the API.
Improperly gapped spark plugs can cause mileage degredation.
Anyway, just some food for thought. Please feel free to refute at will.
David
