what is the reson for low mailage?

All of the above. In addition, if you make only short trips, the engine never has time to warm up to the operating temp and the engine will run rich until the motor warms. This will reduce your miles per gallon.

Apart from the technical reasons mentioned by others, tailgating is also a reason for low mileage. When you follow the next car too closely, without maintaining adequate distance, you end up having to apply brakes frequently. This causes a drop in mileage.

Bad Gas, dirty injectors, worn plugs, cap, and rotor. Dirty filters. Faulty, worn, overgapped spark plug wires.

Always, always, start with the least expensive, common sense approach.

Good luck.

Heavy Traffic

Poor driving habits

Low tire pressure

Poor Maintenance

Driving in a lowest gear.

Tuning may be wrong.

bad driving skills

condition of tyres

age of engine

bad fuel

heavy traffic

condition of roads

bad timing

tyre pressure

bad suspension

worn out plugs

Dirty air filter

Poor driving habits

Bad O2 sensor

Low tire pressure

Bad plugs

Misfire

lack of maintanence

try to drive as reasonable as possible

block in the exhaust

overload

Tune up

Tire pressure

Air filter

Oil change

One or all the above.

Tune up...air filter....tire pressure.....dirty carb.....

Or you just don't drive to the Post office enough....

not enough letters being mailed