2000 Mazda Truck Sudden change in fuel mileage

BIZNESSISMYGAME1

MEMBER
2000 MAZDA TRUCK
4 CYL
2WD
MANUAL
160,000 MILES

Hi I have a 2000 Mazda b2500 with 160000 miles on it but the motor was rebuilt at 109000miles. Within a time span of about 2 tanks of gas (2 weeks) my gas mileage in the city has dropped on average 5 miles to the gallon but it still seems to get its normal gas milleage on the highway. The motor has not had a tune up since it was rebuilt, could that be a problem? The truck has not seemed to have lost any power or perfomance so I dont know what to do to try and fix my gas mileage.

3 Replies

RACEFAN966

MECHANIC
5,029 POSTS

Ok first how old is the fuel filter? How does the air filter look? It could also be an O2 sensor. Is the engine light on?

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Tuesday, September 22nd, 2009 AT 10:35 AM

BIZNESSISMYGAME1

MEMBER
2 POSTS

I am not sure of the age of the fuel filter. I would not surprize me if it is the original fuel filter that came with the truck. The air filter is new, I just replaced it. There are no lengine lights on.

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Tuesday, September 22nd, 2009 AT 4:42 PM

RACEFAN966

MECHANIC
5,029 POSTS

Ok I would get a fuel filter first and change it and see what it does. If needed could you get a scanner to do some live tests so the O2 sensors can be checked. I almost forgot I would like you to check the coolant temp sensor. All you need to do is unplug it and ohm it. If you do this when it is cold like in the morning then get be the ohms reading and the air temp at the time, I will look it up and see if it is in spec. Here is a pic so you know what to look for.