abysmal mileage!

[enobmort42]

how much impact do larger rims/tires have on MPG??

a couple months ago, i was getting ~35+ mpg city/highway with an un-modded stock engine, stock 15" wheels, no DIY cruise. now, i have 17" rims with obv wider tires, and the diy cruise. the engine is still stock. now, with these last couple tanks of gas, i've noticed HORRIBLE mpgs.. just last night, i got 24 mpg, highway. no weight in my car, just myself and my roommate.

i'm at a loss. i've even had the rims on there since july or so.. i understand that i'll take a hit pushing the wider tires, but geez!

the only other thing i can think of is that i used a fuel cleaner solution a couple tanks ago that i got from the dealership. could that really have had that much of an impact on my fuel economy??

any input is great.. i'm borderline nervous that this is here to stay! =\

[yarswiss]

Larger tires will definitely affect your mileage. Since it is more weight and requires more energy per revolution, you will notice a hit on efficiency. If they are wider than the wheel well, they will affect the drag too.

I have used fuel cleaners before and never noticed any significant change in mpg whatsoever. They are probably good at doing just that, cleaning injectors and what not, but you probably can't tell in the numbers.

Not sure if your aftermarket cruise has anything to do with it. It may cause downshifts more often than necessary (in the auto) when under load. Try driving without it for a tank and see if that changes anything.

Basic concepts are: Less weight + slower speeds + good tires, alignment and maintenance = good fuel economy.

[Kal-El]

They shouldn't make that much of a difference. Many members here have 17's and even 18's and still get 35+ mpg.

:iono:

[Altitude]

They shouldn't make that much of a difference. Many members here have 17's and even 18's and still get 35+ mpg.

:iono:

+1 I run 18's and still get between 32 and 38 mpg.

A drop to 24mpg seems to indicate some sort of other problem (unless your new wheels are seriously heavy.)

[MadMax]

No joking here, are you sure no one is siphoning gas from your Yaris?

Also, it could be "winter gas" as well. I noticed I went from a average of 37 MPG to 34 MPG on this last tank. The additional of ethanol does not help either; but your decrease is significantly higher than what I've seen (8-9%)...

[Kal-El]

Doesn't matter how heavy your wheels are, your not going to see a major drop in mileage. People have repeatedly reported getting similarly high mileage with a full load of passengers (800++lbs) as they do with just a driver in the car. In comparison, wheel weight is insignificant.

[enobmort42]

Doesn't matter how heavy your wheels are, your not going to see a major drop in mileage. People have repeatedly reported getting similarly high mileage with a full load of passengers (800++lbs) as they do with just a driver in the car. In comparison, wheel weight is insignificant.

yeah, that's what's so strange about this.. i drove from new york to florida, with a car FULL of my stuff, i mean, there wasn't a single free space at all. i even had socks stuffed in every opening i could, just to fit everything in there. that said, i still got between 33-37 mpg.

No joking here, are you sure no one is siphoning gas from your Yaris?

Also, it could be "winter gas" as well. I noticed I went from a average of 37 MPG to 34 MPG on this last tank. The additional of ethanol does not help either; but your decrease is significantly higher than what I've seen (8-9%)...

i've considered that, and even turned the sensitivity up on my car alarm! when i lived in new york, i noticed the difference in mileage from winter driving, but i'm in florida now. i haven't really altered my driving habits much, except i'm now taking advantage of the DFCO as much as possible! lol

+1 I run 18's and still get between 32 and 38 mpg.

A drop to 24mpg seems to indicate some sort of other problem (unless your new wheels are seriously heavy.)

i know that the wheels aren't lightweight. i'll try to take one off and weigh it, but the most accurate i'll be able to get will be my bathroom scale lol. they were cheap off craigslist, so that leads me to believe they aren't.

could it be the fact that i'm now at 65k miles and just, for the first time, used said fuel cleaner? could there be some clotting... idk, i'm just thinking aloud now lol.


thanks, everyone for the input! i appreciate it. i just filled the tank a few minutes ago and reset the trip, so hopefully i'll notice some sort of improvement...

[127.0.0.1]

did the effective diameter of the wheels change...did you calibrate your odo to compensate ?

[MadMax]

Instead, I would advise checking your speedometer against a GPS. My wheels were put on at the dealership, so I don't know it the speedometer was recalibrated or not; but with my 17" rims my speedo is spot-on.

On my Jeep I found putting on 2" larger tires actually made my speedo more accurate. It was optimistic beforehand, as are most...

[why?]

Another thing to try is to just unhook your battery for a night. Strange things can happen, and who knows what the fuel cleanser might've made your ecu think it saw. But you've had those wheels on for a while, and while heavier wheels will hurt fuel economy, it would be constant.

Have you changed anything else in your car recently? The fuel cleaner might have done something, but I would hope not that. Maybe something else could be wrong. What
did you have to hook the cruise to? The accelerator, or something else?

Also I remember your car got soaked recently, was it bad enough to have gotten into anything electrical?

[enobmort42]

did the effective diameter of the wheels change...did you calibrate your odo to compensate ?

hmm. if i remember correctly, the stock 15's were 185/65/15 and my current ones are 215/45/17. i think the overall diameter changed. is that what you meant? and no, i haven't calibrated my odo... how do i do that? and how would that effect my calculations?

Instead, I would advise checking your speedometer against a GPS. My wheels were put on at the dealership, so I don't know it the speedometer was recalibrated or not; but with my 17" rims my speedo is spot-on.

On my Jeep I found putting on 2" larger tires actually made my speedo more accurate. It was optimistic beforehand, as are most...


the best GPS i have is my phone, and i don't trust that, at all. plus, i've never found it to be truly accurate. then again, i've always considered my speedo to be "the standard" for my speed. would the dealership be able to calibrate it for me? i'll give the gps thing a try, first, though.

Another thing to try is to just unhook your battery for a night. Strange things can happen, and who knows what the fuel cleanser might've made your ecu think it saw. But you've had those wheels on for a while, and while heavier wheels will hurt fuel economy, it would be constant.

Have you changed anything else in your car recently? The fuel cleaner might have done something, but I would hope not that. Maybe something else could be wrong. What
did you have to hook the cruise to? The accelerator, or something else?

Also I remember your car got soaked recently, was it bad enough to have gotten into anything electrical?


yes, my interior got soaked beyond belief lol, but the extent of the damage was to both front seats and the carpet on the far left of the driver's area. the only electrical components that may have been affected were insulated wires running under the driver's side door sill panel thing. they were covered and insulated properly. i'll give the taking off the battery thing a try...

i haven't tried anything other than the diy-cruise, which i had pre-mpg drop, the wheels, which was pre-mpg drop, and the fuel cleanser, post-mpg drop.

[docB]

Big wheels and tires are personal choice. If you like the look, let the mileage go. The heavier wheel and tire is not the only issue here. It is the larger distance from the center of rotation that is the big problem. It is easy to imagine a figure skater doing a spin. When arms and a leg are close to the body spin speed goes up. As the arms are put out away from the body, the skater slows. Same skater and weight, but slow spin when mass moves away from the spin axis. This is why a high wire walker carries a long pole. Performance can benefit from shorter side walls but only to a point. A larger overall diameter will make acceleration suffer. Less movement usually has the driver push on the gas more...less fuel economy. I'm looking to use 14" BBS wheels with a 185/70/14 tire for next summer. I 'll report milage at that time. Currently I have less than 4300 miles. I have averaged just over 40mpg with a one time high over 44 mpg.
I think the gps is way more accurate than an odometer. I just got a newer model and it recalculates much faster, aquires sats much faster and has better featuers than one I got for the wiffe two years ago.\
Madmax, an Altima I had '05 was off 2-3% on the odometer. I think it hurts the lease holder as the clock reads more miles than you drive.
doc

[r3b3l]

I used some engine treatment in a bottle once in my motorcycle, it clogged the injectors bad and the engine seized. It was like someone chewed a whole pack of hubba bubba and put it in my engine. Had to have it scraped out at a mechanic garage. The same would happen to a car engine if too much was added.

[nemelek]

Instead, I would advise checking your speedometer against a GPS. My wheels were put on at the dealership, so I don't know it the speedometer was recalibrated or not; but with my 17" rims my speedo is spot-on.

On my Jeep I found putting on 2" larger tires actually made my speedo more accurate. It was optimistic beforehand, as are most...

You car also check the odometer against the highway mile markers.

[Sidicas]

Instead, I would advise checking your speedometer against a GPS. I agree.. If you can hold your speed for more than a couple minutes (straightaway on flat level surface), GPSs can be VERY accurate at determining your speed.

My Yaris speedo is showing about 2.5 MPH too high on stock 15" wheels..

[supmet]

I realize this is an old thread, but going from heavy 215/45/17 from a 185/60/15, is an extra inch of diameter.

First, your speedo is off by about 3 miles at 65. Second, the extra inch of diameter pushes most of the tire weight out an extra inch, and the farther away from the center of a circle you are, the more rotational inertia it has, and the harder it is to turn the wheel. Not to mention the tires and rims are both heavier. Anyone telling you to expect over 30 mpg is lying or selling something.

[docB]

The greater displacement of mass only makes its ugly face known during acceleration. Starting and stopping as in city traffic will make a bigger difference at the pumps than racking miles on the interstate.

[junorico24]

Get your car serviced, change oil, air and oil filter. I recommend 32 psi front and 34 rear tyre pressure.If you take care of it you will probably see an improvement in mpg. Unless something wrong with your gauge.The Yaris needs to be freshened up to keep it happy.

[djct_watt]

Rotational Inertia = Mass x (Radius^2)

You're better off making your wheels wider than making them bigger in radius (diameter). Just wait till you kill your brakes too (increasing RI has negative effects on both acceleration AND deceleration)!

Everyone swears that big wheels are sporty. . . but they're not. Every purpose built sports car doesn't have big wheels just for the sake of having big wheels. They have big wheels because anything smaller will not fit over the gigantic brake discs. The rule of thumb is to get the SMALLEST wheel possible that will clear the brake caliper. Proper sport tires (with a high PSI and stiff sidewall) will not flex under heavy loads. Take a look at F1 or NASCAR. They BOTH take corners at 150+ MPH and none of those cars have rubber band tires. . .

Granted, it's harder to shop for a proper street tire for a smaller diameter wheel. But unless you have a BBK, anything larger than 15", IMO, is just for looks.

[MadMax]

Big deal, most of the mods on this car are for looks. Anyone thinking they'll get high performance out of a sub-compact is kidding themselves. The Yaris is a great-handling car, but it will never be a straight-line rocket unless you turbocharge it. I am impressed with how well it will go around corners, I usually leave sports-cars in my dust in the turns; but once the road straightens out they blast by. Doesn't matter, I've made my point...

[djct_watt]

^ agreed. . . but big heavy wheels turn this already slow car into an 15 sec 0-60, horrible gas mileage, terrible braking pig of a turd.

But to each their own. Some people are in no big hurry and could care less (or not notice) any of the above stuff. But it's usually the guys with the biggest wheels and most cosmetic mods that are trying to race from street light to street light, driving like morons, and endangering everyone's lives on the road.