I have a 1999 Nissan Altima SE-L (automatic) with 107,500 miles on it.I've had it for about 2 years and I've noticed that the gas mileage has dropped. I'm getting about 14 MPG when I drive hard (accelerate fast, etc.), and about 17-18 MPG when I keep it in drive and don't push it too hard.

I need to fix this, so I ordered a new fuel filter, Vision Motorworks performance spark plug wires, and OBX Racing performance spark plugs.

After I install those 3 parts myself, I am going to take my Altima into a mechanic to see what they can do about the gas mileage...

I need your reccomendations of what I can do, or have a mechanic do to improve the mileage. For one, I am going to have them profesionally clean the fuel system.What else do you think could fix this problem?

Please help me out, I know that the people on this forum are very knowledgable.

Thank you very much!

I would have gone with NGK plugs, the same kind that it came from the factory with. Do the normal stuff; air filter, fuel filter (as you mentioned), check air pressure in tires, and other regular tuneup stuff.

-Jerome

just like what JeromeS13 said just keep up with the regular maintenance , clean or replace filters, run additives to help clean fuel system . i was having the same situation and did all those things but i found out it was the gas. regular unleaded was giving me the worst mpg ever so i had to go back on premium gas, i went off it cause of the price 3.16 a gallon now its more but before i was getting about 20mpg and now i closer to 30mpg and i also started on synthetic oil. its a huge differnce. good luck!

i would have gone w/ ngk iridium IX's. recently before i got them changed, my 240sx was getting like 17mpg-18mpg. now just after the plugs alone, my mileage went upto 21mpg. that or maybe your case might be due to old o2 sensor. speaking of which i gotta get mine changed...