Terrible 22 MPG, all highway

[carrie21]

I have a 2006 Corolla CE Automatic. Since I moved FROM Pittsburgh, where I drove all city miles, up north, where I drive all highway miles on Rt. 28 to get to work, my mileage has become terrible. This was in August. I didn't pay much attention to what it was before I moved, but it was in the low 30s.


Now that I am driving all highway, it has lowered to the very low 20s.

This past tank I got 260 miles, filling up when the fuel light came on, and on a tank that holds 13.2 gallons, this is approximately 21 MPG assuming there was still a gallon in the tank.


So:
-I currently have 9190 miles on the car.

-The majority of miles I drive are highway miles on Route 28.
-I fill up at many different gas stations and use Regular 87 gas.
-My tires are properly inflated, I regularly change my oil, and I have just cleaned my air filter.
-I am easy on the gas, and never “gun it” while driving, and I go about 70 on the highway.
-It's just me in the car, it's not weighted down!!!


I emailed my dealer about it, but from what other people have said, they aren't going to do anything about it.


It just really ticks me off that it says that I should be getting 39 MPG and I get almost half.

[GoPitt68]

Hi Carrie - another Pittsburgher here - Ironically I drive Rt. 28 as well every day to work (From the airport all the way out to New Kensington).

I have a 2006 Corolla S (have had it for a year)...I get about 40 mpg. Usually around 400-430 miles from fill up to time to fill up again at the Get Go.

Not sure what you're doing wrong. One big thing is the 70 mph...Try doing 60 and you will see a big difference. Your mpg exponentially goes down the faster you drive. And Pittsburgh is hilly, so doing 70 up a hill can sometimes mean that you are "gunning it" even though it doesn't feel like it.

Make sure your tire pressure is good 30-32 psi.

Not sure what else to tell you.

[tnmk]

Speed won't effect it that much. I have a 93 with a 3 speed auto (no overdrive) and still get 34 HWY doing 70 plus.

I hope someone here can tell you something. With miles that low your mileage should only be getting better, although maybe not noticeable, as it breaks in.

Some bad gas maybe? How many tanks have you noticed this for?

[GoPitt68]

Yeah it sounds like something is definitely wrong...I drive 40 miles to work and 40 miles back, 5 days a week, so that is 400 miles...and I get that, and then some, on a single tank...and that's mostly highway and also includes major traffic through downtown during rush hour through the Ft. Pitt Tunnel. I would get it checked out.

[Flashmn]

if the emissions check out ok, then theres nothing mechanically wrong about it.
A good tattletale sign is emissions readings are out of spec.

[falnfenix]

sounds like bad gas. pick one gas station(or one brand of gas) and watch your fuel economy for awhile. don't go for the cheapest, either...some gas stations water their gas down.

[carrie21]

I have noticed this for months...I fill up at many different stations...BP, Getgo, Sunoco, Shell...whatever is cheapest. I don't stick with one gas. That's what I thought it was at first....


Thanks for the suggestions. I didn't get an email back from my dealer today, so I will call them tomorrow.

[darcsyde]

change all your filters (air/fuel), change oil & plugs, run a Fuel System Cleaner through your system, check tire pressure, and stick to one gas (me personally always premuim, but others use regular). Every once in awhile through an Oct Boost in the tank. You should see your gas miles go way up

[ghost_ryder35]

could be more than just one gallon left in the tank, usually the light will come on with around 2.5 - 3 gallons left. that would change your mileage to 25.5mpg which still is horrible considering all highway. what you should do next time you fill up is fill up when the light comes on and then divide the number of miles you drove by the number of gallons you pumped in the car. that will give you a more accurate reading of what your mpg is.

[Flashmn]

Every once in awhile through an Oct Boost in the tank.

Octane boosters dont actually raise the octane that much. More of a placebo effect.

Also calculating economy by using the tanks meter/driving as a measuring device will give rubbish as an outcome, if it was a laboratory experiment with controlled conditions it would give a just answer, but normal driving you have so much variables that drop the mileage and cause errors in measuring that its just silly.

[falnfenix]

Originally Posted by carrie21

I have noticed this for months...I fill up at many different stations...BP, Getgo, Sunoco, Shell...whatever is cheapest. I don't stick with one gas. That's what I thought it was at first....

yep. i'd get the fuel filter changed, and pick one brand of gas - stick with that for a couple of months. when you fill up the tank, are you watching the amount you're putting in? it COULD just be a faulty gauge, as well.

so here's my suggestions:
change fuel filter
pick one brand of gas and stick with it - do NOT go for the cheapest gas around, as some of the cheap ones will water their gas down
watch the amount you're putting in the tank. does it match up with how much is shown lacking on the gauge?

it COULD also be the added ethanol, on top of all the aforementioned factors.

[tnmk]

I agree with changing the fuel filter, but anything else, with less than 10,000 miles on the car shouldn't make much diff. And really the fuel filter "shouldn't" need it either. But maybe you sucked something up.

Ethanol shouldn't make more than 1 mpg (2 at the most) diff either. Otherwise I agree, stick to one brand of gas and set your trip odometer each time and do the math that way.
Check all of your spark plug wires for a good connection too. I've seen that happen b4.

[Flashmn]

"sucking something up" doesnt show as a decrease in mileage, it shows in a non working engine. A filter is pleated and it will take a substancial amount of dirt before it will show any signs of losing fuel pressure. When fuel pressure goes down, emissions wont go up, but your engine wont operate that well.

Sparkplug wires with bad connection will be noticed during acceleration. Like I said before, take the car to a shop with an exhaust gas analyzer and have them plug it in. If the readings are within spec, theres NOTHING MECHANICALLY WRONG that would decrease the mileage. Exhaust gas analyzer is a good tool to see what condition your engine is.

I'm willing to be, its just your method of calculating it thats causing you to think that the mileage is gone down, when the truth is something else.

[Limnos]

How far are you driving now? I notice a big difference in fuel consumption between winter and summer driving because in winter it takes the car much longer to warm up. If I only drive a short distance in the winter then my car may never warm up fully at all and may be running rich during my whole trip. You said you moved in August so you're comparing winter driving with summer driving. My car only gets about 22-24 mpg in winter for short-distance driving vs. upper 20s for highway in winter.

In the for what it's worth department, I have a webpage on fuel consumption for my cars at:
www.umn.edu/~haskell/Corolla/index.html (I just noticed this page isn't working at the moment so check again in a few days if the URL doesn't work). One of the definite cycles I notice is the change in mpg with the seasons.

As another person pointed out, calculating mpg using the gas gauge and tank size isn't very accurate. Instead, fill your car up until the auto shut-off on the pump turns off. Drive the car, until you're down about 3/4 of a tank and then fill up again until the auto shut off (you're basically trying to fill the tank up to the same point each time). Note the miles driven between fill-ups and use that to calulate your mpg. Do about 3/4 of a tank rather than just a gallon or so of driving because you'll never fill it up to exactly the same point twice, and this will reduce the error. Do this a couple of times and you can get a reasonable average estimate.

On the 39 mpg manufacturer's rating, I believe those are always under optimal conditions and unrealistic. For example, I recall reading once they drive the car in a lab on rollers where you don't have any air friction since the car isn't actually moving. If you check some websites on gas consumption vs. speed you will see cars in fact do use quite a bit more going 70 mph. vs. 60, though we're not talking the 10-15 mpg difference you're talking about.

Another consideration is gas formulation. I know in this region they add ethanol to the gas in the winter. Ethanol doesn't have the same energy rating as gasoline, so you don't go as far with a gallon of "oxygenated" gas. Again I'm not solid on the numbers, but I think if you're used to 30 mpg then you only get 28 or 29 mpg.

Anyway, adding together a bunch of the bits and pieces could reduce your anticipated mpg a bit and account for some of the difference.

[tnmk]

I agree with Flash for the most part, I only mentioned the spark plugs because I like to check everything when I know something is wrong. And come to think of it, I would assume he is right about the fuel filter, if it were plugged up uou would probably notice a difference in performance as well.

Good luck and get the exhaust gas tested.