What does gas consumption depend on? I always use premium fuel and was able to get at least 330-350 miles before the empty light came on; I’m not an aggressive driver, have AT, don’t use A/C anymore (Chicago weather) but lately have been using heat. My empty light went on at 270 miles last night That's less than 20 mpg.


What could have caused that???

 

a number of things

-your driving habits (do you high rev or do spirited driving?)
-temperature
-a/c and heater on? (they use a lot of gas)
-city vs. highway driving (stop and go driving eats up a lot of gas versus freeway cruising)

 

#1. driving habits.
#2. Tire pressure and air filter

Since it's colder, you can probably run higher tire pressure and you'll get better gas mileage. Make sure your air filter is not dirty. If your in stop and go traffic all the time than I wouldnt expect to get much better gas mileage.

Also, don't listen to TypeRS, the AC uses alot of gas, but the heater does not. The heater only opens a valve that allows coolant to enter your heater core. This does not use gas in any way.

Also, this has been discussed a billion times before. try searching before you post.

 

question a little off topic... on AT probably MT too, if you downshift to slow down and the car revs up does it consume more fuel? i remmeber this being talked about before but havent looked 4 it yet... maybe this could be a reason?

there might be some other problem if your getting 20 mpg, im getting 25 in this crappy city now, when i was getting closer to 28 29

oh yeah one more thing, idling, i used to leave my car on for 5 minutes or so with the heat on last year waiting to go into school. soon as i stopped doing so my gasmilege significantly went up

 

I always get worse mileage in the colder seasons. I started a thread on this a while back. I think the colder temps cause 2 things to happen 1/ - because the colder air is denser the computer compensates with more fuel, and 2/ the car takes longer to reach normal operating temperature and runs very rich in the meantime.

If all else is equal (driving habits, city vs highway, etc), my vote is for temperature.

 

no, you are actually using no fuel at all when engine braking.

 

i didnt think so cuz the throttle wouldnt be opened more than at idle, yet the revs are high, does the fuel injectors cut off or something?

 

 

I drive about 80/20 highway/city. It's a little unusual because I don't remember getting such low numbers last winter.


I'm due for an oil change soon so I'll ask the dealer to check my tire pressure and air filter.


Thanks all!

 

You can definitely change your own air filter. Also, the dealer may charge an arm, leg, and thigh for one. Try looking into K&N for about 40 dollars for a better quality filter. Doing this saves you a few bucks.

When you are driving on the highway, its been said that crusing about 55-60mph is optimal for mpg. Be sure not to slam on the gas and keep at a constant speed. Also, having your windows down will hurt mpg as well, since you are taking on resistance.

Check your tire pressure as stated, be sure your filter isn't clogged, and also clean the TB if necessary. This is a constant problem on my current car ('97 Nissan Maxima) and i clean the TB every so often.

How many miles is on your car?

 

I get 16MPG with spirited (4000~5000 shifting) driving in TL. Now that's far off from advertised 20MPG city.

I find 1.winter gas gives crappy mileage 2. airconditioner or any electronics 3. underinflation 4. idling in traffic

No matter how slow I go (shifting at 1500-2000), when I hit traffic I get 18MPG

 

Just hit 12,000 two days ago (2004).

 

Someone said the car runs rich when the engine's cold...yep, I would add extremely rich, almost to the point where the car loses noticable power until full warmup. Tires are a major factor....I'll go 36/34 front-rear.

This has been posted on other threads but....if you think your AC is off you may be mistaken. You will need to manually shut it off to ensure the compressor is off, even if using heat and you will not be able to shut it off at all when the defoger is on (full defog or floor/defog). To ensure its off make sure you push the AC button to get the signal and if you come back from using a defog feature again ensure you shut it off again.

 

I've lost about 1.5 mpg in the last month, but I am pretty sure it has to do with the termperature. The winter tires may also add a slight bit more friction.

 

You bring up a good point. But when I manually shut off the AC and only adjust the temperature, the interior quickly becomes a steam bath.

 

[QUOTE=fdl] I think the colder temps cause 2 things to happen 1/ - because the colder air is denser the computer compensates with more fuel, and 2/ the car takes longer to reach normal operating temperature and runs very rich in the meantime.

So if temp affects mpg wouldn't having a CAI make the engine run rich all the time? I just got an injen CAI and my first tank resulted in 24.5mpg instead of the usual 26.5 I get. I was wondering if it was becuase of the CAI, but in the past people have said that a CAI would result in better fuel economy if driven in the same manner. What's the deal?

 

That's only half of it, the warm up cycle is a lot longer. Ever notice that the engine likes to idle at about 1500 for the first minute or two when it's below freezing... It's also pushing thicker oil when it's cool.

 

Cold outside temp causes longer warm up time. The ECU is programmed to enrich fuel mixture until a certain temp is dectected by the Engine Coolant Temp sensor (ECT).

 

gotcha, so once the engine itself heats up, the fuel doesn't run so rich. So the CAI shouldn't affect my mpg. thanks

 

Yup, once the engine is warmed up, the ECU has another program to keep the air/fuel ratio to 14.7:1 during normal driving.

 

LOL, and I thought I didn't drive mine much and I'm at 14400 (2004).

do you fill up at the same gas station? maybe you got a batch of bad gas.

 

I hope it was only a batch of bad gas. I refueled today at a different station so we'll see if mpg improve.

 

Also, a lot of people are under the presumption that when you are first warming up the car at the beginning of the day, you should NOT let it warm up for more than a min. As crazy as it sounds, the best method would be:

1.) start car
2.) idle for no more than 30 secs-1 min
3.) drive very slowly (under 2k) until temp gauge slowly rises


Starting and warming up the car for for 5-10 mins kills a lot of gas. It's also not good for the car as well

 

Wow, I can't believe no one has posted the correct answer.

The reason gas mileage is worse in the winter is because there are different additives added to the gas (summer vs. winter blend) so that cars can start easier during cold weather.

 

Some of the things mentioned do affect gas mileage negatively but no where to the point where it would cause a noticeable decrease in gas mileage (low tire pressure, warm up time, etc.).
Or at least no where near the effect that winter blend gas has on gas mileage.

 

Well, its a good thing you got the "correct" answer then.

Her mileage went from around 25mpg to less than 20mpg and its all because of winter blend?

 

this is very interesting. are there any links or articles to back this up? i'm not challenging, just curious.

 

 

That alone doesn't explain the whole deal.

 

summer gas in CA is supposed to be worse than winter gas since it is supposed to be lower pollution (since so many people drive in the summer). i dont think we have additives for cold start since it snot that cold here.

my tsx has about 1000 miles on it, and in well in mixed driving , a lot of it being heavy traffic and lots of driving that is maybe just 4-10 miles i'm getting about 21mpg.

thats pretty sad for a tsx, but traffic and stopping and starting kills any car. so if you do any of that type of driving yeah it will kill your milage. we need a tsx with idle stop and hybrid start for the city.

 

Here you go. Government information on seasonal fuel:

http://www.epa.gov/orcdizux/rfgecon.htm

Average energy content for summer fuel is 114,500 btu per gallon while winter fuel is 112,500 btu per gallon. This is a 1.7% difference. That means that roughly 25mpg with summer fuel will equal about 24.575 with winter fuel.

As you can see, it is not that much difference.

If you don't think that driving with low tire pressure makes that much of a difference, I dare you to drive with 20 psi in your tires. Your MPG will drop so fast you'll think you have a hole in your gas tank.

 

I have noticed worse mileage in my car also. Usually, I get @ 28 mpg, last three fill ups, I am down to 25-26 mpg. If most people started to get worst mileage at about the same time, I'd guess it has to do with the temperature changes, but I do not remember this happening last year.

 

That is sooooo true. Just the difference between recommended 32 PSI and 38PSI is quite noticeable.

Another factor that would refute the seasonnal gas argument is that if this were the only factor, we would all experience a sudden drop of mileage at one point during the year. This is not the case. MPG patterns drop and increase at the same rate as weather does. At least such is the case for me.

BTW, I've been testing with acetone for a while, and though it's sort of difficult to get an accurate comparison since the weather is constantly deteriorating, I do find that my MPG numbers don't tend to drop as fast as should have normally.

So, when the weather becomes a little more stable and predictable again, I will get back to doing some serious comparison tests with acetone. I'll try and do it on a track for even more controlled conditions this time around.

 

A/C yes. Heater, not-so-much. Heat is a waste/bi-product of the engine. It has to get rid of the heat one way or annother, might as well blow some into the car. The only extra energy used for heat is the fan and that is minimal.

 

1. I never said low tire pressure did not make a difference.

2. If you're driving around with 20 psi in your tires, then you've got other issues aside from gas mileage.

A drop from 40 psi to 35 psi will not make a significantly noticeable difference.

 

Uhmm.. the "one point during the year" is late fall/early winter?

 

might want to watch this
Top Gear attempts to drive a V8 Diesel Audi A8 for 800 miles on ONE tank of gas...and they do explain how to maximize ur fuel economy

http://video.google.com/videoplay?do...949&q=top+gear

 

watch the video ^

 

Smartass. The MPG figures don't drop all of a sudden, they do so as progressively as temperatures do.

And BTW, a difference of 5PSI will definitely vary your MPG by a lot more than what winter/summer gas change would.

 

You want to get technical? Lets get technical.

1. I never said that you said that low tire pressure does NOT make a difference. If you read what you said, you said that it doesn't make a noticable difference in gas mileage. If you re-read what I wrote, you would notice that I never said that you said it does NOT make a difference, only that it DOES make a difference.

2. It's not uncommon for one tire to be low and not notice it. Whether it be 20 PSI or 25PSI, alot of people don't pay that much attention and it's not uncommon for people to drive on it. A tire with 25psi won't even look very low, so how would people notice?

3. A drop from 40psi to 35psi will not make a significant difference, but a drop from 30 to 25 will. Obviously the law of diminishing returns applies, as filling your tires up with 80psi will not give you better gas mileage than filling it up at 70 (assuming non trucks). Obviously you want to optimize your tire pressure to get the best gas mileage and the best traction.