Gas Mileage is dropping.

[vic7c]

I have 2008 that I have owned since Oct 1 2012. Approaching 105,000 miles. Notice mileage has dropped from 30-35 to about 25 miles per gallon this winter. I've been told this is normal but I don't remember it lowering in previous winters. I have not gotten a tuneup...I have gotten regular oil changes in 16 pt. look ins with the deal I made..Just got new brakes and tires a few months ago. Could the new tires have caused a problem if not aligned right or should I just get a tune up (maybe check fuel injection)...should I go to a Toyota dealer or stick with the place I get free oil changes, which is a large dealer but doesn't regularly work on Toyotas?

[enviri]

mileage does drop over winter but dropping to that extent is a bit much. I would assume with the 16pt inspection they checked air filters and the such, but yeah i might suspect fuel injection.

[tmontague]

to put it in perspective I usually go from 5.5L/100km to 6.7L/100km from summer to winter. I'd personally wait until spring time and see if it goes back, if not then likely something going on which could be a bunch of things

[Bluevitz-rs]

If it doesn't recover there a good chance the AFR sensor is loosing resolution with that much mileage. But tires can also effect mileage too.

[why?]

New tires will absolutely drop gas mileage. So will winter gas. Have you had the transmission fluid changed? That will also drop gas mileage when it gets really dirty. Check the tire pressures, too low will cause worse gas mileage. I'd pump it up as high as you are comfortable with, I personally go the highest my tires say they can be inflated.

[Kaotic Lazagna]

Could be the brakes??? The pistons may not have been reset and are touching the rotors too much. The same with the rear if you replaced the shoes, may have been over adjusted and the shoes are riding the drums.

If you got extremely sticky tires, that'll cause a drop in mpg.

Spark plugs may be fouled by now (I think they're supposed to be changed at 120k). I know I changed them in my previous Yaris at 61k.

MAF sensor may be dirty, as the TB may be as well.

Winter gas blend drops the mpg some, and even more so if it's a bad batch of gas. I remember getting a couple bad batches of gas in my previous Yaris, and my mpg went down about 8 mpg. How quickly were the pumps flowing the last few times you filled up?

[malibuguy]

What everyone said.

Tires are a major player, tune up, dirty maf (i clean mine every 15k) your brakes and winter fuel

Maybe they have your rear brakes adjusted up too much

[vic7c]

Thank you everyone. I called Munro which did my brakes and tires and they were mystified. They don't have email.(really) and said I could print this out and bring it in.

[edmscan]

I wouldn't worry about it .. my Yaris I am getting about 20 MPG US now in the winter compared to about 39 MPG US in the summer.

So a decrease about 50% in my gas mileage during the winter.

[malibuguy]

I wouldn't worry about it .. my Yaris I am getting about 20 MPG US now in the winter compared to about 39 MPG US in the summer.

So a decrease about 50% in my gas mileage during the winter.

My car usually drops 3-4mpg for winter. Then i put my grille blocks in and I nearly get all of it back

[NYC-SE]

I wouldn't worry about it .. my Yaris I am getting about 20 MPG US now in the winter compared to about 39 MPG US in the summer.

So a decrease about 50% in my gas mileage during the winter.

50% is way too big a drop. Maybe something else is going on with your car.

[MadMax]

Agreed, a couple of MPG for winter gas is normal; but not 30-35 MPG down to 25 MPG.

You've got another issue.

[Motzking1]

You definitely have something going on here. That's just too drastic of a change not to be. With no check engine being illuminated that kind of Narrows what the problem could be. I will run down a quick list of possibilities from most likely to least likely.
1 the mass airflow sensor located on top of the air filter assembly has become contaminated.
2 the air fuel ratio sensors are oxygen sensors as some call them in the exhaust system before the Cadillac converter have become contaminated and are working extremely slowly. They work on being heated by internal heaters and exhaust temperature so this problem possibly could get worse with extreme cold weather.
3 your fuel injectors have been contaminated and are plugged and the spray pattern is very poor leading to poor fuel atomization.
4. There is something wrong with your battery or electrical generation system. I have seen ones with internal plate shorts in the battery that cause the battery to have a very low ohm rating. This cause the alternator to work at 100% duty cycle all the time and dragging down the performance of the engine and the overall gas mileage. Also all modern cars require a very steady good supply of electrical current and a poor battery can cause all kinds of wacky stuff

Sent from my SAMSUNG-SM-N900A using Tapatalk

[tarkus]

Put in new plugs and clean or change the MAF sensor. Also change the air filter, unless it's already been changed recently. Those are the basic things you need to do. Then check the mileage again.

Sent from my LG-D801 using Tapatalk

[Motzking1]

Put in new plugs and clean or change the MAF sensor. Also change the air filter, unless it's already been changed recently. Those are the basic things you need to do. Then check the mileage again.

Sent from my LG-D801 using Tapatalk
Why would you replace spark plugs. There is no engine misfire. That is not the problem here. And engine misfire would illuminate the malfunction indicator lamp or a check engine light. Replacing the spark plugs at this point for anything other than maintenance will not help the problem.

Sent from my SAMSUNG-SM-N900A using Tapatalk

[tarkus]

Nothing to do with misfiring. Heavily used spark plugs degrade engine performance.

Sent from my LG-D801 using Tapatalk

[Motzking1]

Nothing to do with misfiring. Heavily used spark plugs degrade engine performance.

Sent from my LG-D801 using Tapatalk
Heavily used? They haven't even reach the factory maintenance interval of a hundred twenty thousand miles? And I would like for you to explain the mechanism of action of how a used spark plug in any fashion that is working perfectly normal is going to have any adverse reaction at all on the engine. There is a federally mandated very sophisticated monitoring system to make sure if there's any issue whatsoever with the spark plugs that would cause any incomplete burn or anything all that would cause an incomplete burn in the cylinder that would eliminate a malfunction indicator lamp mil. The systems are extremely sophisticated and extremely effective. Hundreds of millions of dollars of research shared among all manufacturers has gone into designing these systems to be extremely effective. So you want me to disregard all of that and believe that you know better when to replace the spark plug?

Sent from my SAMSUNG-SM-N900A using Tapatalk

[alias06]

Heavily used? They haven't even reach the factory maintenance interval of a hundred twenty thousand miles? And I would like for you to explain the mechanism of action of how a used spark plug in any fashion that is working perfectly normal is going to have any adverse reaction at all on the engine. There is a federally mandated very sophisticated monitoring system to make sure if there's any issue whatsoever with the spark plugs that would cause any incomplete burn or anything all that would cause an incomplete burn in the cylinder that would eliminate a malfunction indicator lamp mil. The systems are extremely sophisticated and extremely effective. Hundreds of millions of dollars of research shared among all manufacturers has gone into designing these systems to be extremely effective. So you want me to disregard all of that and believe that you know better when to replace the spark plug?

Sent from my SAMSUNG-SM-N900A using Tapatalk

If I am reading your post correctly you are referring to the O2 sensors giving a MIL when something goes wrong. As sophisticated as they are, they do not always tell the whole truth to the problem. There are many steps involved in the system before it will actually trigger the light. One example of this would be for an issue to happen more than once within a certain drive cycle such as if a single misfire was to happen within 500 miles of driving the light will not come on but it doesn't tell you that you had a misfire. But let's say that you have a misfire every mile you drive, that'll more likely trip the light. Just because you don't get a MIL doesn't necessarily mean everything is operating at full potential. Also OP stated that the mileage is at 105K miles, I wouldn't say that is too far off from the 120k you stated. Some mechanical items fail earlier and some lasts longer, its all subjective to abuse and maintenance.

[tarkus]

Motzking, we're talking about real life here, and the fact is that changing the plugs at around 100k miles is often beneficial. Members of this forum have proven it time and time again. Now let's get back to helping out the OP with his actual issue.

Sent from my LG-D801 using Tapatalk

[SirDigby]

it doesn't make sense to loose ANY fuel millage in the winter time, if anything I would think it would go up. colder, denser air burns more hot and would bump compression causing less throttle action. winter fuel usually contains less corn, so it also burns hotter and easer, also increasing compression. colder air over radiator and block should reduce temperatures, increasing thermal efficiency of block to dissipate heat. I have lost about 1.5 mpg only because I go looking for parking lots and ice patches to play on...

[Bluevitz-rs]

That colder air requires more fuel because it's more dencerer than hoterer airs. Also, cold starts use a lot more fuel while the engine gets up to operating temp. But yes the engine will make more power with less throttle input with colder air. On a long drive there's probably be a negligible difference.

[scratchpaddy]

Cold air is essentially like having a bigger engine. You get more air (denser), with more oxygen, allowing it to use more fuel and make more power. You can then use less throttle, but engines are less efficient (less power produced per unit of fuel) at smaller throttle openings due to pumping losses.

Elevation has an even greater effect. Air gets much less dense at higher elevations. I always get much worse fuel economy at sea level than I do way up in the mountains.

[tmontague]

I can attest that as soon as winter fuel comes to my neck of the woods fuel mileage drops about 75-100km per tank regardless of temp changes. Some years it is already cold, other years its still warm.

There is a very noticeable difference and this is not due to changes in driving as my driving week to week stays about the same.

Where I live this is due to emissions standards being less stringent for fuel in the winter months, they also have an anti freeze additive. These factors lead to lower quality fuels that costs less for the companies to produce but the trade off is poorer fuel efficiency and a more dirty burn.

The prices used to drop about 8 cents per liter as soon as winter fuel went on line, however the last year or two the prices haven't dropped and they've decided to just keep them the same. Then when summer fuel comes back on the prices go up 10 cents. As long as we keep bending over...

[WeeYari]

The prices used to drop about 8 cents per liter as soon as winter fuel went on line, however the last year or two the prices haven't dropped and they've decided to just keep them the same. Then when summer fuel comes back on the prices go up 10 cents. As long as we keep bending over...


Not true. I have every fuel purchase logged going back to Feb 2007 and there is no pattern decrease and subsequent increase in price associated with changes in gasoline formula.


Sent from my iPhone using Tapatalk

[tmontague]

That's been my experience except for the last 2 years. It is also been talked about within the gasoline industry that winter gas is cheaper to manufacture due to the lower emmisions requirements in the winter months

[why?]

My gas mileage can vary widely in the cold. I just managed 37 mpg and was thinking that was way too low, but checked and last winter I was getting the same. Compare that to easily hitting 45 and topping out at 49 mpg in the summer.

As was mentioned, there are a bunch of reasons why there could be nothing wrong with your car and the gas mileage can just drop because it is colder.

[ncp13]

Is it automatic or manual transmission?

[matti]

FWIW, I typically get about 42mpg or so during the summer, and about 32-35mpg during the winter (5MT).