My Mileage Is Going Down. Please Help
 

I'm trying to figure out why my mileage has gone down. I'm driving the same way, and through the same routes. I was getting between 39-40 consistently driving at 75 mph. Now I'm getting 37-38. I know this is not a huge difference, but it's significant to me. I'm hoping it doesn't go down any further. I've noticed this in the past 5 tanks. Has anyone else had this problem? What can be causing this loss of mileage? Please help:confused:

might be because of the quality of fuel. doesnt it get worse in the winter or something like that? im not to sure about it.

Me too...what goes!
 

Hey ephnit,

I've been wondering the same thing. My mpg has also dropped this past month or so. It must be the gas.

I had been averaging 32-33.5 mpg for the past 59,000 miles, now all of a sudden, I've been getting 29-31 mpg! I've been driving the same, but I have since lost as much as 25-40 miles per tank.

Having said that, I am presently experiencing normal mileage again on my most recent tank of fuel. Hopefully, the refineries are formulating the fuel with more energy again. Funny how I was getting the worst mpg when the prices were at their highest. Now since the prices have softened, I am getting better mpg once again.

-macbuddy-

I have an AT sport, and have been using Chevron gas. I've heard that it is one of the better ones to use.

Perhaps it is the weather. So far the coldest its been while driving is 50 degrees. Do you guys think that it is cold enough to make a difference? I also went like a block on a street that is being worked on. It was really rough. Maybe somethings loose now. I have also noticed that the air in my front tires is going down faster compared to the ones in the back. I'm just trying to think of anything that may have caused the lower mileage.

If the weather is cooling off and you are running your engine any length of time to warm up the car, you're going to get lower fuel economy. Don't forget this.

Check with your fuel provider's website and see what ethanol content there is in your fuel. If the ethanol content is increasing, that will reduce your fuel efficiency because ethanol has less energy in it than gasoline does.

Also:

Add the fact that cooler, denser air is less fuel efficient than warm air. In order to get the same air/fuel ratio, the computer adds more fuel to the incoming charge in order to prevent a lean condition. You make more power with cooler air, but you also lose fuel efficiency. That's another reason that nitrous works to create more power. Not only does it add oxygen, but it also cools the incoming air/fuel mixture.

Its not unusual, especially with the gas supply limitations. The refiners change the recipe for gasoline (gas has dozens of chemical components with 'typical' similar to octane, C8H18 , but a lot of other organics besides the additives) to get the most out of every barrel of crude. The result is changes in the energy content of the gas. It may vary from 110.000 to 118,000 btu per lb of combustion.
Naturally the lower the energy content the lower gas mileage. It does occur more often in winter.
And its also why ethanol laced gasoline yields poorer mpg as well. Ethanol has only 80,000 btu/lb as I remember.
Check to see if ethanol is in your gasoline; in SC most all gas stations pump 8 - 10% ethanol but as temperatures drop they can add a little more.
And cold starts: the colder the more gas used, the more cold starts the worse mpg. In Canada that could be 3 to 4 mpg, or more.
A drop of 1 to 2 mpg at 30 mpg would be entirely normal in NM if you only do a couple of cold stars per day..

Tires
 

Can having tires that are not filled with the same amount of air drastically effect mileage?

What he said... :p

If even one of your front tires had a 5 psi drop from normal the increased rolling resistance could affect your mpg.

How does making more power equate to less fuel efficiency?
That should mean less throttle to get same rpm.

heres a good article:
9 reasons why your winter fuel economy bites! - MetroMPG.com


cold air is more dense = more drag = less mpg
winter fuel = more ethanol = less mpg
lower tire pressures
more rolling resistance
etc


I'm with Mahout on the cold air intake.
I have read that colder air may reduce fuel atomization though... :popc:

exactly, therefore, increasing fuel input/fuel sprayed = less mpg:(

I'm starting to feel better about the lower fuel economy. I have inflated my tires again this week because they were off. When should I go for a tune up? Also, how often should I change my air filter? I haven't done either so far. I have 9500 miles on my Fit.

You can remove the filter and lightly tap out loose dirt but there isn't anything else you can economically justify. If you haven't changed oil you should be close enough on the meter to do so if not past... and use the proper weight oil, 0W-20 not 5w -30. And change the filter with evry oil change. The little filters now used don't have enough filtered contaminants capacity to go longer and the filter goes on bypass.

Check your alignment.

Mine has dropped quite a lot as well, I figured it was because my car still has less than a 1000 miles on it and it is getting quite cold out, my first two tanks were 33.4 and 34.1 respectively...now currently on this tank I'm somewhere are 28.9 huge drop, I haven't changed any driving patterns or routes...strange...

Again, note refiners are changing gasoline recipes to get more gallons per barrel of crude. those recipes have less energy per gallon hence less mpg. And naturally, lower ambient temperstures mean more gas consumed during start-up. The more cold startups or the colder the weather, the lower the mpg.

transmission fluid
 

Can having less than needed transmission fluid cause mileage to drop?

If its just a tad low mpg theoretically will increase due to less drag on the gears; if, however, the oil is too low the gears will suffer more wear and subsequent failure begining with loud gear roar.