What can be making my gas mileage bad?

I have a 1992 Nissan Sentra. It's a small 4 cylinder car. It runs great but the gas mileage is horrible. What could be causing the problem?What can be making my gas mileage bad?
It may need a tune-up !!
have you had a tune up lately?

get regular oil changes?

checked tire pressure?

carrying anything heavy in the trunk?

do you drive fast, with lots of quick starts and stops?What can be making my gas mileage bad?
check air filter maybe needs tune up
Tons of things but lets start with simple. Driving slowly, slow acceleration will help. Make sure your tires are properly inflated, they will lose some air when it gets cold. Make sure you have changed spark plugs, air filter, plug wires. If none of that helps then take it to a shop and have them check the computer maybe you have a bad sensor that isn't setting off the check engine light.What can be making my gas mileage bad?
Take your foot off the gas pedal. You probably run that little 4 banger ragged, don't you? Its not a V-6 or a race car so stop trying to make it run like one.
Tire pressure, proper tune up and oil change or driving conditions/ habit are common. If you smell gas you may have a leak.
Low Tire Pressure can cause a drop in mileage...Check your Air Cleaner and make sure it is clean. Dirty Fuel Filter can rob you of some efficiency. And badly gapped or dirty Spark Plugs can cause a drop in mileage as well...
could be one of many problems or even a combination.

tire pressure

air filter

fuel filter

tune up including plugs and possibly wires.

oil change
tune-up,drive a little slower,tire pressure
its old. ever tune it? check tire pressure 5 pounds low can cut 2/4 mpg... throw can of injector cleaner in gas..
You could have a bad oxygen censor. If so that will be a cheap and easy fix, but you will likely need to carry the car to the dealership so they can test the censor to see if it is bad.
Low air pressure in the tires can cause bad gas mileage and its a safety problem too for braking and bends. Check the correct figure in your car handbook and inflate them to the right figure.



Your driving style can make a difference. Try to accelerate smoothly, as if there was a tank of goldfish in the back and you don't want the water to slop out. My driving instructor told me this.



If you have a manual gear-shift and a rev counter, look at how many RPM you are doing and pay attention to whether you are in the right gear for the speed you are doing. Ask on here what is the right figure for your type of car.
driving with the windows down (seriously), always using the radio / hi-fi / air con etc contributes loads to increased fuel consumption.



could just be that you do a lot of town driving though - freeway routes will usually use less gas as there's less mucking with changing speed and gears etc.
When was the last time you had a tune up? Dirty Oil filter,Dirty fuel filter, fuel injectors being dirty and low tire pressure are just a few things that could be contributing to you poor mileage. I would recommend you take your car to a reputable garage, not a dealer, they charge too much. I have had great sucess with NAPA affiliated garages, they are very honest and reasonable. Good Luck
One of the causes my be a clogged air filter. Go have a oil change and change your air filter and put some fuel injector cleaner in your Fuel take this should help . Also not having the proper tire pressure in your tires will kill gas mileage so check that too
Alot of thins. I once got really bad mileage, and had my tires checked and was shocked! They were supposed to be like 30 or 35 pounds of air in them, and I had 6, 10, 12 and 4! I don't even know how they got that way! Well, I guess by not ever checking them. But I learned my lesson on that one.
there is several possibilities. Could be oil needs changed, could be needs new wires and plugs, could need an air filter or fuel filter. could be a fuel regulator( if this one is it, it can blow your motor over time if not fixed). and there are also some sensors that can cause this too.
Most of these are good answers. I noted a problem not mentioned. And that is clogged muffler.
low tire pressure, incorrect timing bad plugs possible wheel bearings if you hear noise from the wheels-also I am not sure but I think in 1992 they cam out with a automatic fuel sensor for the plugs and/or injectors if you do not have a carburetor that could very well be it, but firts try some injector cleaner
cars recirculate hot gasses form the catalytic convertor back to the engone. This line has no sensors just physical parts so it wont show on a computer diagnostic. a hole rusted in the pipe will cause an issue. A mechanic or even you when it is cool can clamp a small pacth over it from the outside using hose clmaps and a suitable piece of "muffler patch" metal.
A bad oxygen sensor or an engine temp sensor. The engine temp sensor may be different than the one for your gauge. If it thinks your engine is cold, it will push more gas into the cylinders.