tor_el

I'm surprised no one has mentioned the O2 sensor. Yeah, it's more of a last ditch thing, but if the O2 sensor has gone bad, it can cause your car to run rich. Rich=more fuel=bad fuel economy.

bbarbulo

iTrader: (2)

an O2 sensor (I ran a test on my saturn) caused me to lose a mere 2 miles per gallon. that's less than 20 miles on a full tank. I ran my car for an entire tank with the o2 sensor unplugged and recorded my mileage. then i put a brand new O2 in there, and performed the same driving, same everything... I did the test 4 times in a row, driving for a week unplugged, and a week plugged in.

anyways, I would think it's obvious you need to locate and fix your vacuum leak, then check your coolant level and your FITV to fix your erratic idle... then come back and report your mileage.

wintertime usually results in a loss of 100-130 kms per tank compared to summertime, primarily cuz I let my car idle to warm up for 5 minutes every time I go somewhere, plus the cold air requires a richer mixture to ignite (fuel atomization is affected by the temp).