I have a 00' I30t and I seem to be getting about 250 mile to the tank, it seems that the mileage is terrible now.

What should I check/replace myself before taking it to the dealer?

About 15,000 miles ago I replaces the air filter and fuel filter.

I am thinking maybe spark plugs?

I have had not SES lights at all.

 

you are using premium, right?

 

spark plugs, O2 sensors, and check your ecu for the KS code... you might have to replace that too.

Even if you drove all city, you should be getting near 300 miles per tank.

 

i just changed my spark plugs and i do notice a difference, more gas milage now.

 

Yep, 02 sensor would be a main cause, but you should see a check engine light I would assume if that was the case.

 

O2 sensors can go bad with out tripping the CEL.

 

I would have never guessed that, but then again, I just bought my I30 on Friday...

Most cars would throw a code...

 

Its not just the I30... most cars can have that happen.

 

Very well could be an oxygen sensor. Sounds like a bad Knock Sensor to me.

If you decide to replace the KS here's my write-up: http://forums.maxima.org/showthread.php?t=500569 Get an oem sensor either from a dealership or ebay.

 

I noticed your write up was for 95-97. Would this be the same for an 01'? I know in those years, not much has changed. I just want to clarify.

-Cheers.

 

When i bought my car it had 116k on it. Luckly the guy that had the car before me took care of it except he didn't do the 100k service. So I changed the spark plugs (NGK Platinum), Fuel Filter, Air Filter and I use octane booster with every tank. I got about a 2-3 mile increase in Gas mileage. I get around 250-275 miles down to 1/8 of a tank. When I bought the car from the Infiniti Dealership they also had replaced the Knock Sensor and all the O2 Sensors. Hope this helps.

 

It is the same.

 

I have a 99 i30 and it gives me about 375 for a tank of gas, which includes 80% highway and 20% city driving. I always use premium fuel.

 

I have 90K, original plugs, beat the crap out of it, all stop n go city driving, always premium. I get about 22 mpg. Yeah, I gotta get around to changing the plugs; as soon as finals are over.

 

So one should replace all o2 sensors or one specific one?

 

Replace all of them.

 

we got 4 of them right?

 

I'm the retard of this community, but I can only remember 3. Two on the y-pipe. 1 on the front down-pipe.

And why does it seem I get better gas mileage than most everyone here? I use cumberland farm's premium, and I consistently get 24.5-26.8 MPG. My record was doing just under 70MPH on the interstate. Filled up 3/4 of a tank and calculated 29.1MPG.

 

From what I understand, it depends on whether your I has Cali (NLEV) or Federal spec emissions. The Cali (NLEV) has 4 total O2 sensors. Two before precat & another two after the precat. The Fed spec exhausts have only 3.

 

I get 375 to 400 miles on a tank just as the low fuel light comes on. If I really try and take it easy, I'll see 400 steadily.

I wonder if you would also benefit from checking tire pressures, unloading any extra weight and an alignment?

On a less significant results level, are you using synthetic oil?

After all you've done (plugs too) and the abovce, if you're not at at least 350 per tank, there's something going on that's beyond easy & simple.

(I also just turned 147K miles.)

 

bother checking tire pressure?

 

I only get about 300 miles on 15 gallons driving all city. That is 20 mpg which is about right.

 

Hey Guys, I didn't want to start a new thread for this silly question, so I hope no one minds a slight hi-jacking.

I don't think I'm getting very good mileage either, but I've never kept track. I've never quite understood how you can accurately track the mileage. Reason being, how do you know for sure that you're putting the exact same amount of gas in the tank each time? How do you guys record this?

 

On our cars, it is particularly easy.

Wait till the low fuel light comes on before you fill it up with gas next time. Fill it immediately when the light comes on.

Reset your tripometer and fill it up with (say...10 gallons just to make the math easy).

Next, drive it like you stole it or normally, your choice.

At the very moment you next see the low fuel indicator come on, record the triopometer mileage.

Divide the recorded mileage by 10 and you have your MPG. So if you got 200 miles on 10 gallons, you got 20MPG.

Now, fill the tank up again with 10 more gallons and record your data again with the tripometer reset. Do this fill/record method several times and you'll have enugh data to be fairly accurate.

Later, you can go back to filling it up all the way if you want and really focus on recording mileage (and refilling) the instant the light comes on to get more data. With several readings, you'll reduce the chances of the light coming on being affected by hills and such (do you have many in Omaha?) as gas sloshes around.

You'll also be able to manage the "reserve" fuel in the tank ...so you'll know that when your light comes on, you got about XX miles to go until you walk.

(Not hard stuff to figure out.)

PS. I got 368 miles on the last tank and with 16 gallons from the last fill up, that's 23 mpg and I've been letting it idle a lot to get warm recently....

 

Right on, Double E. That sounds easy enough. We do have some hills in Omaha, but nothing too drastic.

 

Anyone know how many gallons are left after the light coems on? I imagine it is the the manual... but I dont really feel like getting it right now. 2 gallons or so?

I've also been having some weird issues with one of my O2's. Light comes on, no signal from O2. Thought I may have snagged some wires on the previous snow. A day or so later the light goes away. Next time it snows, sure enough, the light is back. Same code. A couple days later the light goes away again.

Maybe Im getting some unprotected wires wet.? Guess Ill check it out when the ground is dry again. Good news is, my mileage does not seem to have suffered.

 

A simpler way:

1. Fill her up (don't top off)
2. Reset trip meter
3. Drive until half of the tank is gone, or until fuel light comes on
4. Fill her up again (don't top off), remember how many gallons you fueled
5. Take the trip meter's mileage and divide it by how many gallons you fueled

Basically, how many gallons you fueled equeals how many gallons you used. Do it a few times to get an average.

 

I believe it is 2 gallons.

 

Some suggestions

1. Change your fuel filter.
2. Change or clean your air filter.
3. Get a fuel injector cleaning...preferably with a fuel rail flush, too.
4. Get a tranny flush, and use synthetic ATF this time
5. Get an oil change and use s synthetic like Mobil 1 or Valvoline.
6. Clean out your MAF
7. Clean out your throttle body
8. Keep your tank filled. Don't run it with less than 1/8 tank.
9. Have your alignment checked. Also check your brakes.
10. Add an additional 2 to 3 PSI beyond the recommended inflation numbers.


What's your weather been like? Daily temperature?

 

Even though it is not throwing any codes, I recommend resetting your ECU.
Unfortunately Nissan is not exactly known to produce fuel efficient cars especially since around the time of conception and production of your car, gas prices was not anyone’s concern.

http://www.fueleconomy.gov/feg/findacar.htm
I believe your car is 'rate' City 20MPG - Highway 28MPG and avg user 23.5MPG so if you tune up a little, you are at/near mark. My '98 gets around ~21MPG mostly HW but I have a heavy foot.