BMW E36- Drop in fuel economy?
Unless you have an check engine light, changing the O2 sensors will be a waste of time. The engine may have a deeper internal problem with compression considering the mileage on it. Your dumping in more fuel to get the same power as it did when it was new. To me, I'd consider a bigger issue. Compression.
BMW E36- Drop in fuel economy?
Try the water temp sensor.
It senses if your engine warmed up. While the computer thinks the engine is cold, it will run then engine RICH (poor fuel economy). I answer lots of questions here, and lately more and more people are reporting poor economy (and the weather is turning cold). Hmmmmm....
The thing about water temp sensor is that a failed sensor often does NOT turn on the check engine light. The only nice thing about failed check engine light is that it is fairly easy and cheap to replacel
Good Luck
