940 Non-Turbo Year 1995
Fuel consumption: 15 miles to the gallon now. Previously was 22 mpg

Over the past months I've posted about high fuel consumption. I've changed the following parts but fuel consumption remains high. However after replacing the O2 sensor, fuel consumption improved but after several months fuel mileage dropped again and now back to where it was before the O2 sensor replacement. What else could possibly cause high fuel consumption?

Parts replaced:

O2 sensor - After replacement, mileage improved although not to the previous level. Now fuel consumption is high again.

Fuel Pressure Regulator - No visible change in fuel consumption after replacement

Back silencer and tail pipe - Changed these parts only two days ago. I thought that perhaps the previous tail pipe being larger in diameter, could be the cause. Now that I've changed it to the original size, I realize the tail pipe size does not matter, so far as fuel is concerned.

Spark plugs, engine oil, timing belt, accessory belts, transmission oil (flush), kickdown cable - all replaced very recently.

I notice that the gas meter indicator drops much much faster at lest than half tank. When the tank is full it seems the indicator does not drop that fast. After travelling close to 200 miles the indicator will be slighly at below the half tank line. Once the indicator cross this line, it drops very fast, roughly for about 90 miles for it to reach the red line and the yellow light to come on.(The yellow light at the gas meter)

What else could be wrong? Please give me some pointers to solve this perpetual problem. It is not only a pain to my pocket but also I don't feel secure once the gas meter indicator drops below the half tank line.

A friend told me to check the gas refil cap. There wasn't much of a smell when I open the lid and also I don't expect gas to evaporate that fast. Another thing, when I leave the car to idle and get out of the car, I could smell strong gas at the exhaust. There are no black soot around the tail pipe though.

Thanks in advance for your advice.

Laozong