I've been measuring my car's fuel consumption in city driving more than a few times and with 80% city driving i usually get ~20MPG, .... if i drive really gentle (like a normal person) i get 21 MPG. I rarely use the AC.

On Sunday night, i clocked the car at mostly highway driving. I did 250 miles, 97% highway, and since i was driving after 2am in the morning, i was doing 95-105mph at least 30% of the time .... The rest was 70mph+.
When i put gas at the pump.... it looked like i got 22MPG!!!

-- My car is 2003 SE, with AT and 70k miles on it.
I never used the AC. Tires were at normal pressure. All filters are new. No intake. Spark plugs are the original. ~70 degrees outside. 91 Shell gas. 2 people in the car.

Is 22MPG on the highway...given my driving....normal??? Should i worry about it and take the car to the dealer for a check? (i have extended warranty)
Is my city driving 20MPG acceptable?

I know the car was rated at 20 city / 27hw .... but only 22MPG on the highway - made me think a little.

Thanks for any input!

 

Check your tire pressure. The car probably also needs an engine flush and fuel system flush. Use Seafoam once. Get a tune-up.

You do all that and it'll be back to normal.

 

That sounds a little low to me. I get about 27 MPG highway going 70-80 MPH the whole time. Maybe it has something to do with you going 100+ MPH for part of the time?

 

There are your problems.

 

Some info from Edumnds.com

On the highway, the DOE says that every 5 mph you drive over 65 mph represents a 7-percent decrease in fuel economy.

http://www.edmunds.com/reviews/list/...4/article.html

 

and you deffinately get less MPG going anywhere above the 60-70 mph area. i'd say that also had something to do with it.

 

Cruising at 100 mph would do that to your pocket, I mean gas milage...

 

I hadn't noticed the 95-105 part.

Didn't ever occur to you that maybe when you pressed the excellerator down to the floor that you burn more gas?

 

When you say "get a tune up"... what do you mean? The only thing that i have not replaced on my car is the spark plugs. I try to keep it in good shape.
I did a fuel system clean with BG44K fuel cleaner 10k miles ago.
I replace oil (mobil1) and filter + air filter regularly.
Cooling system and AT was flushed at 60k miles.
I am not sure what else i could be missing....other than the sparks

Tell me a little bit more about the Sea Foam? Pros/cons? etc..

Thanks!

 

It did not press down to the floor. I was driving fast but i was accelerating slowly. I was not racing.

 

Also, given your highway driving was only 250 miles, the variation in fill up levels would have an effect on your MPG unless the gas was virtually spilling out of the tank on both fill ups.

When was the last time the fuel filter and air filter were changed? Slow down and you'll get better fuel economy.

Your city mileage isn't all that bad.

 

What part of the effect of engine rpm on fuel economy do you not understand? Quit your crying, stop driving your car like you stole it, and the fuel economy will improve.

 

It still needs to be revved higher (RPM)

 

I am starting to see where the "problem" is.

Air filter was replaced 8k miles ago.
Fuel filter - never replaced! Should i worry about the Fuel filter at 70k miles?

 

There is NO "crying" here. I'm not complaining. I came to ask a question and i got answers. Yes - i know how rpm affects engine gas consumption !!! .... yet i hear that there are people on this forum who drive fast and get better MPG than me.

No need to act all pissed off.....if you are unhappy with my post - ignore me.

 

The fuel filter supposedly never has to be replaced. You might have carbon build-up in your intake manifold. Seafoam will get rid of it. Do a search on Seafoam and you'll find a write-up or two. Very easy to do.

 

Changing the 5th gen FF is a bit different than changing that of a 4th gen, and I also do not think it has as much of an effect as your speed does.

EPA standard fuel mileage estimates are 60mph @~2000 RPM, hardly what any of us drive, even if it is on the "highway".

I have never seen higher than 26, and even that was only once, this I attribute to the simple fact that when I do get 23-24, I'm traveling on average 77-82mph.

Fact is the 4AT Maxima just does not have an ideal gear set to get that great of mileage, especially at speeds most of us drive.

 

Try driving a 5 spd that "cruises" in 5th gear at ~3500 rpm/75 mph.

 

Try doing that with .5 more liters.

Or 1000 less RPMs and .5 more L.

 

You might want to consider using AutoRX to clean out your engine internals, crankcase and ring packs. See www.auto-rx.com and www.bobistheoilguy.com (BITOG).

I would only use Seafoam (haven't yet) through the brake booster hose to clean the intake manifold, which AutoRX will not do.

Given that you have used the BG44K not that long ago, you likely don't need a fuel system additive.

I wouldn't use Seafoam in the crankcase. I would use AutoRX first, then LubeControl LC20 on a maintenance basis and Lubecontrol FP60 later in the gas tank as a fuel additive. See www.lubecontrol.com and BITOG.

 

More info on Seafoam here: http://forums.maxima.org/forumdisplay.php?f=70

You can also find threads discussing Seafoam by using the search function.

Do a search on "gas mileage" to find all the threads where people have discussed their different MPGs based on different driving styles and you will find that your car is behaving pretty normally.

I believe the most "efficient" rpm range is something between 2000-2400 rpms, but someone please correct me if I'm wrong. Assuming that is correct, your driving at 70 and then 95-105 with the 4AT has gotta be more like 3000 rpms and over. I don't have an AT, but based on the fact that my 6th gear cruising rpms is about 2200 rpms at 70 mph, yours has to be more.

FYI, I get about 19 mpg city driving "normal" and 22 mpg city driving conservatively; shifting below 2500 rpms. The best I've gotten highway is 25 because I don't have the patience to keep it at 2200 rpms on an open interstate.

 

Thank you - ALL!!

Looks like there is no need to visit the dealer.

I'll look at the sea foam and the other solutions proposed. I'll rpelace the spark plugs as well. Most importantly - next time, i'll slow down if i want better fuel economy.

 

I would sure like to have a 6-speed in my 4th Gen, Puppetmaster. At 70 mph in 5th gear, I'm about bang on 3,000 rpms or just a touch below, compared to your 2200 rpms.

I can't get 22 mpg city driving, more like 19 and change, but on the highway on a road trip I consistently get 29 or better, but I'm not going over 75 mph and am using CC and no AC.

 

my fuel filter was caked with sediment @ 50k miles. i definetely would replace it at 70k. nissan lists it as a lifetime part but it is a fuel filter like any other that will get buildup. everyone that has replaced it has said they would do it on a more consistent basis. i am shooting for 85k on my next one.

 

according to this article warming up affects your mileage? because everyday i warm up my car two or three times.

 

replacing the fuel filter - i take it this isnt your average DIY job. do you actually have to diassemble the tank? If you changed it your gas mileage isnt realistically going to get that much better, 1mpg if youre lucky?

 

If you drive at the top speed as the Max can ever reach w/ the gas pedal down to floor all the time, I bet you would get <10 mpg.

 

A little extreme example isn't it?

 

Fuel filter replacement thread:
http://forums.maxima.org/showthread.php?t=314172

 

i think that number is just right i get the greatest mileage when i go like 60-70mph

 

Your city mileage looks the same as mine. Your highway mileage (at those speeds) reeks of a math error...

 

thats exactly what i was thinking! i drive mostly city, i mean, sometime i get out on the highway, maybe 95% city, 5% highway, i get a good 320-360 miles on a tank! usually i fill about 15.5 gal