I own a volvo 850 wagon and i replaced the engine on the car and have been driving it for about a month since i replaced the engine, and i noticed that it has poor gas mileage. the mpg on the dash says 15.6 and i think it is worse than that. what could be done to improve the gas mileage?

 

start with a regular tune up
spark plugs, air filter/ or intake.. stuff like that.

 

what kind of driving do you do with the car? Is it all city? If you disconnected the battery, which obviously you did when swapped motors, the ecu starts all over computing average mpg. and if all your doing is city stop and go driving, then your mpg will not be very high.

 

i did the regular tune up, and yes i drive mostly stop and go. but i have another volvo 850 wagon, same year and it got better mpg and i am not quite sure why

 

I would try to do some highway driving and see if your gas mileage goes up any.

 

i'm begining to believe mines bad aswell

i'm doing atleast 50 k on the highway a day and it seems pretty bad, i'm wondering if changing both 02 sensors would do alot or not?

 

Yes, I believe new O2 sensors will make a difference. Chadman, that may be a good place to start. Do you know when either of your O2 sensors were replaced?

 

how will you know which O2 sensor to replace? There's a couple of them right? And since there's no CEL, how will you know which to change?

 

You could try unscrewing them and see if they looked aged and if there's a tone of build up on them.

 

Change the front O2 sensor. All the back one does is monitor how well the catalytic converter is working- it has no effect on performance or economy.

 

so by changing/looking at the front o2 sensor there could be a possibly of better fuel economy?