ive posted this before but ill post it again just a little differently. i was getting bad gas mileage, got 2 new o2 sensors, coolant temp sensor, knock sensor, and a full tune up. mileage was good again for about a week or 2 (got about 260-270 miles out of a tank, mostly all city driving as i drive around for my job) now im back to bad gas mileage (about 200ish to a tank, maybe 210. i threw in some fuel injector cleaner and i just got an oil change today. now i was told to clean the throttle body last time i posted this. so my question is, even if my tb is really dirty, could it really cause this bad of gas mileage? also my car hesitates sometimes when i hit the gas if im not at a complete stop, like it takes a second or 2 for it to start moving. i have no codes in the cel, got 0505. i want to clean the tb as soon as it gets a little warmer out, but is there anything else i should look at? any help would be appreciated....

 

damn... i get more then 400 out of one tank. get a new air filter if you havent done that yet. your car really needs

 

"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: www.maximadriver.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. Sprintmax has a great spark plug changing writeup that can be found here: http://www.sprintmax.com/tails/sparkplug.htm

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: www.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). www.buyoxygensensors.com gets good reviews on this site frequently, and they have good prices. For a writeup, go to www.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 (www.thepartsbin.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 www.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!"
credit to gepetto.

 

yo thanks for posting that, but let me just say this:
my air filter is brand new,my fuel filter is new,all my spark plugs were changed less then 1000 miles ago, i have 2 new o2 sensors, the 3rd is working properly, i have a new knock sensor, and i just put in a fuel additive to clean out the system. i guess i gotta go fill up my tires and see what happens, and i gotta clean my tb.

 

i get different gas milage based on who i buy gas from...if i get gas from exxon, i get 300 to the tank, with 80%+ city driving. if i get the cheaper russian fuel from US gas, i only get 200.

 

another question, the guy who was geting 400, is that mostly highway driving?

 

It looks that spreenyk88 did everything that he could to keep his gas mileage high...Not sure where to look for trouble...I see that the plugs were changed...I hope that they are not Bosch ...If the plug is not an NGK , I d reccomand replacement, eve if the new ones would be coppers...
About the 400 miles per tank: remember that our cars have a 17 gal tank...Lets think that we refill up when there are 2 gal left- that is little over 26 miles/gal. It could be better than that...
Spreenyk88...Its hard to say where your problem is. Maybe I d change the gas station first .You also said that your car hesitates sometimes...Is there a chance that you have an intermitent coil problem ?Not sure if that would trigger the CEL ...Other than that cannot think what should be done...But please keep us posted if you find where your problem

 

Question about tire pressure. I keep mine at 41psi and always considered that to be a standard for our cars, but here I see I can be totally wrong. SO people, at what pressure you have your tires?
(I have stock tires on at the moment)

P.S. I get about 330 miles per tand from highway/city driving but wanna push it up to 400, wonder if that's doable....

(ones going to DC from NYC I got above 460 miles to the tank on the highway)

Edit: I have done complete tune up 3 months ago / engine has 104K miles

 

I get 480 miles from a tank of gas on highway. I don't run NGKs but autolite platinums. Tire pressure is 35 psi cold. I get between 26 and 30 miles per gallon with mixed city highway 29 highway if constant. If mainly city at 45 mph with lights I get 25 to 26 miles per gallon. And I have 223,000 miles plus on my 95 maxima.

Bad mileage, check your tires, plugs, and type of gas your using, then go air filter, fuel filter, and fuel injectors.

If your having problems with your transmission check your fluid.

Very rare you would have bad problems with your maxima.

 

I get 400 plus mileage, however that is with about 50 - 50 city to highway driving and i have a manuel transmission.

 

the plugs i got were installed by my mechanic, which he got from the nissan dealer. i also had a tranny flush in the last 3 or 4 months. the thing with my gas is i get it for free from my job, and they have a deal with the shell station down the street, so thats where i always get my gas from. i always get 93 premium. now you might be reading this and say "he gets free gas why does he care about mileage?" well first if im burning a ton of gas my job wont pay for all of it, and number 2 its only a part time job which i dont think ill be having for much longer, probably only a few months. so i want my mileage to be good. my car is 8 years old with almost 120k, but it should be getting good mileage. if only i had some money i found a 97 gxe with only 32k miles for 8000. but alas i have no money....

 

yep

 

Thanks for info. I am gonna deflate tires now to 35 psi !

 

You might want to go a few pounds lower if your driving in snow and ice 33 would be safer.

 

Try using a gas from a different company. I always use Mobil (91 octane - thats the highest that I get in southern california) and get around 350 miles/tank with almost equal city/highway mix. Once I filled up at a shell station and my mileage went down to ~300 miles/tank.

 

i cleaned the throttle body, it was pretty dirty, but still no increase in mpg. im getting 14mpg right now, and its still hesitating sometimes. now what do i do?

 

Yeah, I have low gas milage as well. I'm going to have to check some stuff in srping time.

 

dido