Low MPG 92 325i E36 BMW
Q My 92 325i is consuming a lot of gas. I’m getting only 14 miles per gallon instead of the usual 20-24 miles per gallon. Tire pressure is ok, air filter and brakes are new. What else can be the cause?
A Your drop in gas mileage could be related to several areas. The first thing is the colder weather: you may simply be letting the car idle longer to warm up. It could also be time for a tune-up, which would include spark plugs, connector boots, fuel filter, etc. If your oxygen sensor has more than 60,000 miles on it, it may need replacing: a worn out oxygen sensor would certainly cause your mileage to suffer. You might also have a vacuum leak in the intake system. There are various areas that are susceptible to vacuum leaks; a very common spot is the plastic fitting at the front of the valve cover on the driver’s side. Also check the hose coming from it and running under the intake manifold to the back of the throttle body. Finally, you may benefit from a good fuel system cleaner and a carbon deposit remover such as Lubro-Moly Jectron and Lubro Moly Valve Cleaner . Unlike those typical, off-the-shelf products from the local car parts chain store, these actually work, and work quite well. We recommend using them in alternating months as an effective cleaning and preventive maintenance routine.