I've been getting very low mpg's this past few months. I filled up 3 gallons exact when it was dead empty, and today it's empty again and i've only done about 44.5 miles

That means a little less than 15 mpg.. Is that possible?

I'm lead footed about 30% of the time, but only to the speed limit and most of the time i'm cruising at 35-45

Drive 6 miles one way and back each day.


Air filter is very old, but could that cause such bad mpg?

 

Lead foot...biggest reason...
Short trips...
Cold temps....
Dirty filter....
Yup....

 

P.S.
Running to very low fuel level is VERY hard on the fuel pump....
It is cooled by being submerged in fuel....
While it is very cold...still not a good habit....Other issues like sucking crapboff the bottom of the fuel tank can be issues...
Try topping off the tank...running till 1/4....then refilling to determine the mpg. Only doing a 3 gallon sample is a pretty poor sample size.

 

Yeah i know that, thx for the info

About 2 months ago i did this mpg test, filled up the whole tank and reset the mile counter, and when the tank was empty it read 230-245 miles which means almost 20mpg while using the same filter and the same driving habits

although this month, -20 Celcius temperatures mean very little traction with all seasons so that may be it..

I'm not sure if i should just replace the air filter or wait till spring and do a DIY CAI ?

Also a question for you if you have a R53
Does your car sound a lot meaner when its less than 0 F? or around that temp
Today it was -9 F and i floored my car when it warmed up and it sounded awesome.. Like Ferrari awesome! also a little louder

 

Colder air = more dense air ...so more fuel can be added = more power...
Same concept as a better intercooler....but free from mother nature.
But little things...like the car running at a higher idle till warm (all cars do this) and the fact the rubber on the tires are more stuff, making rolling resistance higher...lowing mpg...then if you are crunching snow or ice...will not roll as well. Then add to the fact winter fuels...they are formulated with more volitile chemicals to increase the vapor pressure.... Making it easier to start in the cold... Lots of factors....but all add up to lower mpg....
Some info I have read says on a modern computer controled car using o2 sensors, a bad airfiler can improve mpg AFTER the car is warmed up and in closed loop mode...the computer leans the fuel to match the airflow in....car would run too rich in open loop...like right after it is started before the car is warm or wot...full throttle uses stored maps, o2 sensors are too slow to respond for more than cruise acceleration or streaddy speed.
At about $10 for a cheap FRAM/Purolator....I would toss a new filter in....
The filter in the s in the stock box can get pretty gunky due to the intake tube by the radiator sucking in some moisture....

 

15 mpg inluding warm up and city driving in this weather? definently believeable esspecially if you have a lead foot, i really only have 3 good accel spots and i havea 7 mile commute, i get about 21-23 depending on how much i warm up my car, i have winter tires. but 6 miles are 50mph for me, thats where i make up for mine =)

the cold are definently makes a difference like zippy said, my magnaflow when im on it is much louder, no need for a stereo, i saw intake temps this morning of -1 - 3F where is was -4 F here this morning

paper filter is really cheap, replace it till its warm enough to make your own CAI, no need for a K&N filter to slap in there when your going to get rid of the box soon enough, and you should have a few more ponies after you clean =)

 

get a fuelly and keep actual track of the mpg..

 

The very cold temps mean that your car is in 'warm up mode' for longer, meaning that it is using more fuel than it does at normal operating temperatures. Lots of short trips means you are spending very little time up to temperature.

 

I'm getting mid 20's and I'm in Michigan as well. Most of my drive is back roads with a 30 min drive.

 

I'll add -

Colder Temps = Thicker lubricants = more parasitic drag on driveline parts = lower MPG.

As well as low tire pressures too = lower MPG.

And most winter blended fuels contain Ethanol which at 10% is going to also impact your MPG.

(whoops I see Zippy beat me to that last fact).

 

Thanks for the comments guys, i actually use Torque to monitor my mpg but in this week it won't connect to my phone for some reason..

So i guess i'll just wait a month or two and do a DIY CAI as it will sound way better...

Also, i've used Torque before to monitor my MPG's 2 months ago, and it read 23 avg with lead foot, 26 avg if driving like my dad..

I guess the cold temps are a real killer! I filled up with $10 again yesterday and it's all gone after 50 miles :(

Plus i forgot to include that i have a %15 pulley..

Again thanks for your time.

 

You can do an air filter change yourself or many auto parts stores will do it for you for free if you buy it from them. Basic maintenance, like spark-plugs, plug wires could also be the cause as well as very cold weather conditions and your very short drive to work. Winter is very hard on MPG. CHANGE the air filter first, it may never have been changed at all. QUOTE=Husam Hammadi;3870223]I've been getting very low mpg's this past few months. I filled up 3 gallons exact when it was dead empty, and today it's empty again and i've only done about 44.5 miles

That means a little less than 15 mpg.. Is that possible?

I'm lead footed about 30% of the time, but only to the speed limit and most of the time i'm cruising at 35-45

Drive 6 miles one way and back each day.


Air filter is very old, but could that cause such bad mpg?[/QUOTE]

 

I can obviously do it myself, but i'm waiting for it to get warm so i can do a DIY CAI..

Filled up the tank, and today it's very closed to empty and done about 19.5-20 MPG
Not bad but not good either, since my mums car which is a lot bigger gets the same mpg with same driving style..

Hopefully will do a DIY CAI next week since it's gunna be in the 40's..