Low gas mileage can come from any number of places. Let's start with the basics. Keep in mind the following for optimal gas mileage: use 91+ octane fuel, try to keep RPMs below 4k (normal), your car must be in overall good working order (good oil, good coolant etc) and other factors. If you're doing a bunch of 5 minute trips, or its 0 degrees outside, don't expect gas mileage to be so hot. Also keep in mind that different types of gas can have an effect on the mileage. Shop around to find the best gas you can. But if none of these describes your preidcament, read on. Below are some common causes and cures for bad gas mileage.

1) Air filter. The stock filter on the car is a drop in panel filter. If you bought your car used there is a chance that the filter may have never be changed. This would be the time to do it and you have several options: drop in K&N filter, cone filter or CAI. A search on any of these terms will resolve any questions you may have. If you have a cone filter, the filter may be dirty. K&N makes a recharge kit that is available at Pepboys to clean the filter.

2) Fuel filter. The fuel filter is small gray cylinder on the back of the firewall that is to be changed on a 60k service interval. It is often to blame for bad gas mileage, but can be a pain in the butt to change, but it can be done. The filter is relatively cheap from Nissan. Some members reccomend buying a fuel filter for a Nissan 300ZX. Its the same size hoses, but twice the size, so it lasts 2x longer and is doubly effective. The choice is up to you. The writeup to change the filter can be found here: http://forums.maxima.org/4th-generat...ximadriver.com

3) Spark plugs. If you're running anything other than NGK plugs in your engine, or you bought your car used, go get some NGK spark plugs for the dealer. Spark plugs are to be repalced every 60k miles, but rarely are. They will cost about $10 a pop.

4) Dirty throttle body. The throttle body is the first piece of metal behind the intake system. It accumulates a certain amount of dirt and grime. Those who clean it out after long neglect find their car is smoother and that fuel economy does increase. Writeup can be found here: http://forums.maxima.org/4th-generat...w.motorvate.ca

5) Tire Pressure. Stock tire pressure is 29psi. I found recently that mine were at 25 and filled them up and found a substantial increase in fuel economy. If your tires are low, go ahead and fill them up (I filled to about 31, but everyone has a preference).

6) Oxygen sensors. If an oxygen sensor is messed up, it will trigger a Check Engine Light. There are three sensors in total. 2 rest in the respective branches of the Y Pipe (these are the Front Heated 02 Sensors) and one rests in the catalytic converter (95-96) or in the B Pipe right behind the cat (97-99). If any of these sensors fail, gas mileage will decrease substantially. Many sites exist that sell oxygen sensors (dealers will charge a lot). http://forums.maxima.org/4th-generat...gensensors.com gets good reviews on this site frequently, and they have good prices. For a writeup, go to http://forums.maxima.org/4th-generat...w.motorvate.ca, or search around the .org

7) Knock Sensor. This is the bad boy, the code everyone fears. The sensor is actually just a piece of metal that rests under your intake manifold. They cost approximately $110 from various sources (http://forums.maxima.org/4th-generat...hepartsbin.com is usually cited as one of the best). The sensor is not terribly difficult to change, but as my friend Harold described it, "Nissan must weld razor blades under the manifold." Due to tight fitting, the sensor often results in a bloody hand. The writeup for the sensor can be found at http://forums.maxima.org/4th-generat...w.motorvate.ca

8) Dirty fuel system. As a car grows older, carbon deposits in the fuel path, clogging areas such as the injectors. Many modern gasolines are designed to combat this (such as Chevron with Techron) and there are many additives that can be added to gas to clean out these systems. Many mechanics offer a full fuel system clean out for about $50-$75. Many .orgers believe this to be BS, some think the process is valid. The choice is yours.

This is the ticket to good gas mileage! Any other questions can be resolved using the search function, as this subject is discussed quite often. Enjoy!

I have a '96 Maxima with a manual transmission. There is a thin metal plate with teeth attached to the outside of the flywheel that the crankshaft position sensor reads. Does anyone know if this is actually part of the flywheel or if it is a seperate item just bolted to it? If it's seperate, does anyone know what it is called? The one on my car is damaged. I've checked with the parts department of the closest dealer (50 miles away) and they say they can't find anything on it in their system so they want to sell me a flywheel at $300. I'm going to pull the transmission this weekend to find out for sure but thought maybe one of you guys had run into this before.