86 325e poor mpg

[RyanD]

I just picked up this car. Changed the oil and the thermostat and put nrw belts on it. From what i can tell it runs fine bit im getting about 16mpg. 90%of my work commute is freeway.

Whats going on? The only thing i can think of next is a valve adj and a new o2

[indecline]

Spark plugs and oil change.

[101]

Agree with replacing the O2 sensor and plugs if you have no history on them. Check the resistance readings for the coolant temperature sensor for the ECU to make sure that sensor is within spec. Is the air filter clean? Does is smell as if its running rich?

Could the rear diff have been changed at some point? Eta should have a 2.79 or 2.93 ratio for the manual transmissions.

Check for sticking calipers or e-brake. Even a small drag can be significant.

Something is up for sure. My manual eta with a 200K mile motor gets > 30mpg on the highway.

[RyanD]

I will do that thanks.

[MR 325]

Agreed on plugs and o2. I also recommend the valve adjustment and a new cap/rotor.

Otherwise checking the ECU temp sender as well as TPS adjustment is a great idea.

If the intake boot or vacuum lines are cracked replace those as well.