My 04 used to average 23 mpg in a mix of hwy and city driving according to the computer. Lately its been more like 21-22. (I've got about 88k miles on my car). I pulled one of my spark plugs and it was fine. I was thinking of changing out O2 sensors until I priced them at Autozone. There's a total of 4 at ......get ready for this......$262 each!!!! I think I'll live with the slightly lower gas mileage for now. Anyone had to change these out?

 

They're under $30/ea here: http://www.overnightautoparts.com/st...t&make_code=NI

 

That's for the single wire universal sensor and no connector. According to the service manual, the Max has 4 wires. Hummm...

 

The 1 or 2 mpg difference is not much. Low tire pressure, dirty air filter, new gas formula with ethanol, dirty MAF, extra load on alternator (heated seats/defroster), oil switched from synthetic to dino, etc may explain the drop.

It could be a 'lazy' or slow responding O2 sensor but at $262 each I would explore other explanations/solutions. Did you replace the spark plugs at 60K?

 

Too bad you did not catch this problem before the drive train warranty ran out at 60 K miles.

The oxygen sensors may also be covered under the warranty on the emission system components. Suggest you call a dealer and find out if that is the case. I think the emission system components are covered for either 100 K or 120 K miles -- but these are only a guess on my part. Check and be certain. It would certainly be nice if Nissan paid for their replacement.

Like the post by mik said: "Low tire pressure, dirty air filter, new gas formula with ethanol, dirty MAF, extra load on alternator (heated seats/defroster), oil switched from synthetic to dino, etc may explain the drop." You don't say where you live, but the NE has recently gone to 10% ethanol blended in the gasoline and that along with winter could cause much of this drop.

 

They list a 1-2-3&4 wire sensor ....4 wire 43 bux

http://www.overnightautoparts.com/st...1&make_code=NI

 

my car is now averaging 14-15mpg. just plain ridiculous. this is after a synthetic oil change and the air filter replaced. the car is at 37k now. any ideas? i wouldn't think it'd be anything to do with the o2 sensor or spark plugs being at 37k. thanks.

 

Complain to the dealer. Use premium gas only

 

thanks..I always use premium.

Those dealerships never give a crap.

 

Check that air filter. It may have collapsed and is blocking the air flow. I doubt the emission system is at fault. It's so sensitive it would probably light up the SES light. If you think it a sensor, have the dealer check if a OBDII code is present. Some org members have said that emission components have a longer warranty.

 

Here's a readers digest version of the emission warranty coverage (if you have the California emission package, you're in luck!):

Non-California Emission Package Warranty
The longer term warranty under federal mandates only includes a few parts. For any and all Nissan vehicles with a model year of 2004, the federal warranty on emissions control systems is the standard 3/36 except for an extended 8yr/80k mile warranty on the following two parts:

Engine control module/onboard diagnostic device
Catalytic converter(s)

California Emission Package Warranty
Coverage on basically any emission component for 7yr/70k miles, including:

Engine control module/onboard diagnostic device, Catalytic converter(s), Exhaust Manifold, Intake Manifold, Distributor, Throttle Body, Fuel Tank, Transmission Control Module, Torque Converter, Flywheel Crank Sensors, EGI Wiring Harness, Mass Air Flow Sensor, Knock Sensor, Oxygen Sensor(s), Supercharger, ... etc, etc, etc...

Not to mention that with the Cali emissions package, if your car fails any inspection up to 50k miles for any reason, that part is covered. Plus, in my reading, I learned that if you had a Sentra w/1.8L engine or the Altima w/2.5 engine, that's under warranty for 15 YEARS or 150,000 MILES!...

I'm guessing that because you're from IL you're SOL.

 

I hope this is a stupid q but u never know
Did u reset your FUEL ECON button? Press for 3 sec.to reset. As u drive, it will change freuquently. When parked w/engine on, that # drops quickly. BUT- if you're already doing this and STILL getting low teens, then I'm sorry I can't help.

 

Hey, thats definately a very small difference and I am pretty sure that is due to the colder weather gasoline. When the season turns colder, gas stations sell a winter grade of gasoline which is adjusted to help burn better in the colder air and this in turn, reduces gas mileage. With my car, I use to get about 22 mpg and now I am getting about 16, a much bigger difference than you. I wish I was getting 21

 

All of this is true.

 

thanks. I'll check the air filter. I had the K&N Hi-Flow Flat Panel installed about 500miles ago.

 

Oh yeah of course. I reset it each time I have my tank filled up.