l have 05 ford Taurus v6 3.0 12 valve and it has low millage too it is using too much gas 10 mile per gallon what do you think l should do? can you please help me?

Take it to a mechanic or the car dealer and have them look at it. It is possible it is just a simple fix.

get a tune up

oil change
air filter
spark plugs/wires
fuel filter

l would definitely take the car to a mechanic. You do not provide enough information to give any ideas as to other diagnosis.

Your car should be getting about 18 mpg in the city and 25 on the highway.

Take it in ASAP

If you smell gas in exhaust, big problems are to follow.

Could be an injector or a leaky fuel line. Too many possibilities to guess at.

replace the o2 sensor[s] 90% of poor mileage problems on older vehicles

10 mpg is really low - should be better - l had one and it only got 15 mpg. The worst part was the fact that it was such a dog. l could run faster. Best answer - sell it.

Where do you live, l seen lots of areas with extremely cold climates the last couple days. If you are in below -20 like alaska your car will get 10 mpg, l lived there all cars got about that in the winters. Cold air saps fuel mileage especially extreme cold.
If this is the case wait and see when it warms back up.
It was 20 degrees and l went from 21-22 to 15 mpg in my Lincoln Towncar. Thats only at 20 degrees. Think at 40 degrees below that.