donut

Is the mpg supposed to drop in the winter?

I've had the car since september and check my mpg every time I get gas (miles traveled / gallons to full). For months, it was at a rock solid 20 mpg. Then, as it began to get a bit colder, it dropped to 19, 18, then 17 over the course of 3~4 tankfuls. It's been holding at 17 for the last 5 tankfuls or so.

I believe they change the gas formulation for winter here in Chicago and wondered if that could cause such an effect. It doesn't seem drastic enough for a mechanical problem, does it? There's been no discernable difference in the car's behavior.

It has 51K, and I always use premium. I switched brands from Citco to Mobil to see if that might help but zilch.

Eric L.

In Winter the combination of oxygenated fuels (3% lower fuel economy) and cold weather (takes engine longer to warm up, uses more gas) contributes to lower gas mileage. A drop from 20 to 17 is not unusual.

marcel

Gasoline doesn’t atomize as well when it's cold.

funkdaddysmack

Also, generally in winter you'll be running your accessories more, i.e. heater w/ fan speed and defroster and such things. I used to get no less than 30 mpg on my car (not a maxima), but now since it's winter, I've gotten around 26-27 mpg. Yea, yea I know I should be complaining, but almost all my driving now is highway driving, so I've seen a significant decrease.

nigelcmf

So this is my theory and it's not all that whacko really.

In winter, the air is colder and therefore denser. The air/fuel ratio will probably seem like it is out of whack (leaner than normal) The ECU will detect this from the O2 sensors and adjust the mixture to run a little richer....

The good news in all of this is that you should feel a little more power since higher amount of a/f mixture getting to each cylinder

This is just a theory, but it seems reasonable doesn't it? I'm basing this on Turbo/intercooling and cold air intake theories.

SuDZ

Makes sence to me.

SuDZ

matty

iTrader: (54)

And thats why you feel more power when you put on your CAI but not right away...your ECU has to adjust to the change of colder air entering the cylinders

95emeraldgxe

yeah - he's right.....heater, defroster, all that stuff uses gas

mzmtg

iTrader: (11)

The electrical load of the defroster is not so much that it would impact mileage.

nigelcmf

Hehe! glad you agree and don't think I'm smoking dope!

Hehe!

donut

Can't the two be unrelated?

njmaxseltd

iTrader: (19)

I can't believe you guys only get 20MPG I'm always up around 23-26 MPG and on a trip 28-29 MPG. And thats doing 75 MPH. I can get 400 miles on one tank on a trip.

RedMax95

good to hear bc im getting 17 myself and dont much like it

dwapenyi

iTrader: (3)

True, but then the gas atomizing happens in the quite hot combustion chamber. No?

DW

nigelcmf

I was, but I didn't want to be to obvious!

98MAXNY

im getting about 16-17mpg 98se auto with 76k

costcowholesale

iTrader: (12)

what abt listening to your stereo?

nigelcmf

Yeah 17 MPG is really bad! you guys must be leadfooting in first gear all the time. I get 23 MPH minimum. But I do a lot of highway driving too. My average is probably 26-28. I drive a '97 SE 5sp

JdawgX

Wow, 17??? I would be ****ed! I get 23-25 city driving with my 97 SE 5 spd. Not sure how you guys are getting mileage that crappy. Bummer

98MAXNY

i just figured it out. im getting about 18-19mpg and i rarely go over 3000rpm. half city half highway

Steve Marsh

I get about 475-500 miles per a tank full (strictly highway). I use Valvoline Syn power fuel injection cleaner once a week. The fuel system cleaner is used once a month. Otherwise the only other fuel injector/system cleaner i use is Chevron! Texaco systems-3 super unleaded and or Sunoco Ultra 94 always! 96se 161,260 miles Amsoil 0w-30,Amsoil SDF Oil filter, Redline "Water Wetter", Amsoil ATF. Amsoil foam Air filter. THROTTLE CLEANING every 2-3 weeks! Religious preventative maintenance I literally feather my gas pedal (super smooth acceleration)

RedMax95

i do full city driving, lots of traffic, hills, stops, mines a 95 obviously, i am cleaning the tb soon, so we will see how it helps

njblk97se

check your tire pressure. From what I understand, changes in weather affect the pressure, which affects your gas mileage...

nigelcmf

Weather does not affect the pressure in your tires much .... if at all! But if your tires are underinflated you'll lose fuel economy

matty

iTrader: (54)

Temperature can affect the tire pressure by 10psi..Learned that on the weather channel
no but its true

iwannabmw

iTrader: (3)

The change in tire pressure is about 1 psi per degree of ambient temperature, so 10 degrees= 10psi= a lot of wasted gas.

nigelcmf

It's 1 psi per 10 degrees! Over a 50 degree drop that's 5 psi. In CO if it was 1 psi per degree, a tire at 20 psi in winter would be at 100 psi in summer! I don't think so!

http://www.tiresafety.com/service/serv_nav1b.htm

iwannabmw

iTrader: (3)

Doh, my bad. Too many 1's and 0's

donut

First place I looked. I actually check it fairly regularly, and it wasn't off by more than 1 or 2 psi. I don't think that was it, although I promptly corrected it.

I want to know how you guys are getting so much better mileage. I changed the air and fuel filters a few months back and ran some fuel system cleaner through as well (chevron techron concentrate). What are you guys doing different? Is it a lot of highway driving? I do about 75% city.

Justin95SE

iTrader: (1)

my car was going 400 miles on a tank, i usually had about 3 gallons left when i filled up which is roughly 27 mpg. it dont do that no more though, weird huh. plus i was driving more city at that point because i took a new job.

dwapenyi

iTrader: (3)

That would kill your mileage right there. Plus you're an auto, it gets worse city mileage than the 5 speed.

DW

marcel

I believe the issue is the tempeature of the fuel (gasoline) when it is injected into the cylinder. If it's cold outside, the injected fuel is also cold.

donut

But the EPA mileage rating for an automatic is 21/28, so shouldn't I be getting something in between? Plus I thought about it and the "city" driving actually involves a lot of cruising rather than stop-and-go, so perhaps 60~65% city is a better measure...

dwapenyi

iTrader: (3)

I wouldn't take the epa figures as 'golden', so to speak. Jst a good ballpark figure. There are times that I have actually gotten 19 mpgs, and other times I've even gotten 30 mpg. OK, the 30 mpg happened only twice in the 2 years that I've owned mine
I achived that 30 by concentrating and using the cruise control alot. DOn't think I'll do it again. I just wanted to know how economic I can make may car. It did quite well.

I suggest you try driving your car gently for a whole tank of gas. See how that goes. If your mileage is still bad, then give it a tune up. Feul filter, air filter and maybe even spark plugs. Keep in mind that spark plugs are supposed to last 60K miles or so.


Oh, one more thing, do you drive for a very short time alot?? Like drive for 5 minutes then stop?? Then it could be also that for all the times you drive, you car does not reach operating tempaerature. The car does not drive economically till its fully wramed up. When it's cold, the idle is high, drinking more fuel, and the ECU, knowing that your car is cold, uses a fuel mapping that is very in-efficient. so in-efficient that you can smell gas when your car is cold. This is not for just our Maxima. Its the norm for every modern car on the road.

DW

donut

Now, this makes sense. Not sure how much of my driving is this short, but this is information you can sink your teeth into...

Btw, fuel & air filters were changed a few months ago. And thanks for the help.

2DMax

iTrader: (2)

Winter driving is bad for gas economy.
When I was commuting 2 miles to the train station and back, my winter milage was half that of summer driving.
On road trips, I would get a good 27-28 MPG, my dad gets about 30 MPG when he drives my car on trips, but he's doing 55 !

RedMax95

my newest news: got the prcai, i was getting 17, filled up today and got 18.3, and this even includes a 10 min idle, 6+ sound demos for friends which wastes gas quite well, and a tendency to hit it a little harder than usual to hear the sound, in other words i wasted more gas but still got better mileage

Nick97SE

iTrader: (14)

I was wondering why my fuel economy has gone down. I used to be able to get 400 miles on a tank, but now I'm down to 300, which stinks. Looking forward to Spring time for some new mods and better fuel economy!

Later,
-Nick