WTH is going on with my mileage??? - UPDATED with more stumpage!!!

[Zenmervolt]

Tires definitely are not it. My mother uses the same tires on her '98 Maxima and saw no mileage reduction from the OE Toyo Proxes.

Double-check the inflation pressures.

Also, Minnesota gets a helluva lot colder than WA, and gasoline is formulated differently there in the winter (more anti-freeze elements). See what your summer mileage is. I would routinely drop 5 mpg in the winter when I was living in Ohio, and Ohio's not as bad as Minnesota.

ZV

 

[imported_Hi]

have you changed your motor oil to see if it helps

 

[iamwiz82]

Originally posted by: njmodi

Originally posted by: iamwiz82

Originally posted by: njmodi

Originally posted by: iamwiz82

Originally posted by: njmodi

Originally posted by: iamwiz82
Spark plugs are due, if they haven't been done yet.

The plugs might be at faulty, but they are definitely not "due" as a maintenance item - his car has platinum plugs, with 100k replacement intervals.

Sorry, that is a silly thing to believe, IMHO. I can get spark plugs for $2/plug, $12 seems like a small price to pay.

Show me some NGK platinums for $2 each.

Why must every import driver swear by these? It is almost as dumb as quadruple fires, +84s, or, even plutonium plated. It's amazing how much money companies can make on stuff like that.

Maybe its because time and time again Maxima owners have seen driveability issues and performance drop-offs using any other plugs.

Do you have a Maxima?

I thought they never have problems? That's all I have ever heard from here.

So it costs you guys $72 to replace your plugs? My Champions are a $1.79 a piece. I think I'/ll stick with mine. :laugh:

 

[StageLeft]

Thanks Skoorb! BTW - how do I get my car on your Nissan Page .

send me a pic and/or info to PM. I have a queue of people I need to add, but I've been increasingly distressed by my procrastination lately, and I anticipate getting to them this month!

 

[lobadobadingdong]

n/m

 

[StageLeft]

I thought they never have problems? That's all I have ever heard from here.

Most of the people at maxima.org do recommend OEM plugs or, if you're cheap, $2-3 NGK coppers and change them out every 30k, but even those are not quite as good. I've only tried OEM, so I can't say whether other plugs are good or crap in our cars.

 

[njmodi]

Originally posted by: iamwiz82

I thought they never have problems? That's all I have ever heard from here.

So it costs you guys $72 to replace your plugs? My Champions are a $1.79 a piece. I think I'/ll stick with mine. :laugh:

They don't - as long as you use NGK platinum plugs...

:beer:

 

[njmodi]

Originally posted by: Skoorb

I thought they never have problems? That's all I have ever heard from here.

Most of the people at maxima.org do recommend OEM plugs or, if you're cheap, $2-3 NGK coppers and change them out every 30k, but even those are not quite as good. I've only tried OEM, so I can't say whether other plugs are good or crap in our cars.

Not to go completely off topic, but the NGK coppers work ok - but they do show wear before 30k. I just use the platinums - I figure, every 60k means I'll probably have to replace them 2 times while I own the car.

 

[BatmanNate]

Are your tires under inflated?

 

[J0hnny]

Originally posted by: Hi
have you changed your motor oil to see if it helps

Same problem in my Civic (but i drive a lot of city), here is what i did to fix:

0) Fuel injection cleaner (chevron techron)
1) New fuel filter
2) New spark plugs
3) Changed oil and oil filter
4) Cleaned air filter
5) New plug wires
6) Cleaned throttle body w/ throttle body cleaner
7) Reset ECU

Milage improved by an extra 50 miles to the tank after that (city driving). I still think I can do better, so I'm going to

possible 8) Clean IAC
possible 9) change ground wire

 

[TwoBills]

I'm with the OP. This is a stumper. I don't think the tires would cause that much of a drop, maybe a little. And he's raised the psi w/o any change. My original thought was the air filter, but he covered that. Maybe a 1/2 mpg drop can be attributed to the oxygenated gas. If it's starting ok when the weather's a little moist the the plugs are probably ok.

I'm running a supercharged Frontier w/75k and original plugs. My mileage dropped about 1 1/2 mpg when winter started, as normal. Gotta get to some major maintenance. Come on Spring!

Only thing I can think of is carbon buildup in the combustion chambers. I don't know if Maxima's have this problem. Might try some of that stuff that Pat Goss pushes on his radio show. BG 44K or something like that. Couple of tanks of Chevron high test wouldn't hurt either.

Keep us posted on this one. PS: How's your alignment?

 

[Mill]

Originally posted by: njmodi

Originally posted by: iamwiz82

Originally posted by: njmodi

Originally posted by: iamwiz82
Spark plugs are due, if they haven't been done yet.

The plugs might be at faulty, but they are definitely not "due" as a maintenance item - his car has platinum plugs, with 100k replacement intervals.

Sorry, that is a silly thing to believe, IMHO. I can get spark plugs for $2/plug, $12 seems like a small price to pay.

Show me some NGK platinums for $2 each.

I can get NGK plats for 2.50 a piece. I know a distributor.

 

[njmodi]

Originally posted by: Mill
I can get NGK plats for 2.50 a piece. I know a distributor.

Hello friend. Long time no see... let me buy you a :beer: Are you going to hook us up or what?

 

[Biggerhammer]

I had been thinking low tire pressure, but you checked that.

Your MPG started dropping before you moved, so the gasoline most likely didn't change back then.

I could certainly see a drop whe you moved from your rainy clime to the Icy North (different gasoline with more alcohol, lower effective tire pressures due to temperature, different road conditions, more warmup time, et al) but again, change started in Washington.

At this point, I'm guessing. Have you had your brakes looked at? One dragging pad could do this. Water in the tank you would notice. 50K with good preventative maintenance is too soon for a Nissan to get valvetrain wear or the like.

I'm stumped too.

 

[flot]

Originally posted by: iamwiz82

So it costs you guys $72 to replace your plugs? My Champions are a $1.79 a piece. I think I'/ll stick with mine. :laugh:

I just think it's funny you're talking about changing spark plugs, period. I don't remember the last time I changed a set of spark plugs at earlier than 50-60k intervals, which equates to, what, once every 5 years? Who cares? The "labor" (either mine or someone else's) can far outweigh the cost of the plugs, depending on the engine. But regardless - this isn't 1972 - changing plugs has been one of those things you do once or twice while you own a car for at least the last 5-10 years.

 

[iamwiz82]

Originally posted by: flot

Originally posted by: iamwiz82

So it costs you guys $72 to replace your plugs? My Champions are a $1.79 a piece. I think I'/ll stick with mine. :laugh:

I just think it's funny you're talking about changing spark plugs, period. I don't remember the last time I changed a set of spark plugs at earlier than 50-60k intervals, which equates to, what, once every 5 years? Who cares? The "labor" (either mine or someone else's) can far outweigh the cost of the plugs, depending on the engine. But regardless - this isn't 1972 - changing plugs has been one of those things you do once or twice while you own a car for at least the last 5-10 years.

His car is at 47,800 miles. I'd say that is fairly close to your interval, correct?

 

[KK]

I've have the same trouble on my windstar, I usaully get 22-23 MPG in the winter time, no A/C and about 18 MPG in the summer using A/C. But this year for some reason I've been getting horrible mileage, around 17 MPG. I did get new tires back in december, but I believe it started just prior to that. I just reset the MPG computer in the dash today so I'll see what it averages out to, maybe I'm getting better mileage now.

 

[KingPhil]

During warm months with my 03' Hyundai Sonata 4 banger, I was pulling in about 28MPG, or about 400 miles / tank.

Now, in the middle of winter, I'm only getting about 290 miles / tank.

That SUCKS. Then again, I'm driving more city now too.

Still, I can go 2 weeks on 1 tank, so I'm ok I hate winter.........

 

[kranky]

As long as we're grasping at straws, are you sure your gas cap is sealing properly?

 

[sao123]

Washington -> Minnesota = More hilly terrain?
Elevation can change your gas mileage because of the difference in air density... maybe need to have your carb/injectors recalibrated for different mixture.

Other suggestions
Check -> Filters, Plugs, Wires, Coil, Timing, Turbo Charger (if any), try plus instead of premium... (u can have too much octane), switch to full synthetic oil, check transmission fluid level & change trannny filter, full grease and lube job, tire pressure, wheel alignment, gas cap pressure.

 

[iamwiz82]

If we are really going out there it could be a malfunctioning ECU or injector, too.

 

[psteng19]

Originally posted by: J0hnny

Originally posted by: Hi
have you changed your motor oil to see if it helps

Same problem in my Civic (but i drive a lot of city), here is what i did to fix:

0) Fuel injection cleaner (chevron techron)
1) New fuel filter
2) New spark plugs
3) Changed oil and oil filter
4) Cleaned air filter
5) New plug wires
6) Cleaned throttle body w/ throttle body cleaner
7) Reset ECU

Milage improved by an extra 50 miles to the tank after that (city driving). I still think I can do better, so I'm going to

possible 8) Clean IAC
possible 9) change ground wire

Good advice.
For the OP, I'd start with some FI cleaner, throttle body cleaner and then sparks.
Also, the fuel filter suggestion is good - the change interval on those is 30-40k.

My gas mileage dropped from 45 mpg to 35 mpg because of winter

 

[AMDZen]

Originally posted by: iamwiz82
Winter gas
Extra weight in the tires
Poor alignment
Spark plugs are due, if they haven't been done yet.

All these are good tips and also get a new Air Filter. I suggest replacing it with a K&N or similar.

 

[Don Vito Corleone]

Just to reiterate, because I keep seeing some things that are covered in my initial post:

- plugs are fine
- winter gas is not the primary explanation (the mileage dropoff happened in temperate weather in Washington)
- I have replaced the air filter, but I had been using a new Amsoil filter (similar to a K&N, but arguably better)
- tire pressure is fine
- the tires I replaced were also all-season, although they were "Sport" tires
-Minnesota is FLAT, much more so than Washington, and has no altitude of any significance

Is it possible my alignment is off, even if the car tracks straight and true? It has no tendency to pull to either side. That is the only suggestion that seems like a potential explanation to me, so far.

Thanks again for all the suggestions!

 

[StageLeft]

I bet it's not alignment....