Fuel Economy

[Ziv]

Originally Posted by Idjiit

No, typically people inflate the front tires between 3-5psi higher.

Really? glad I asked. Then how should I match the tire pressure? if the tire said it's 32 let's say, and should I get the front up to 35ish?

[Idjiit]

Originally Posted by Ziv

Really? glad I asked. Then how should I match the tire pressure? if the tire said it's 32 let's say, and should I get the front up to 35ish?

If you want to follow the "max pressure" guidelines of the tire and the max is 35psi, then set the front to 35psi, and the rears to 32psi or so.

[punch]

umm how do i do the math, I got 598Km on my first tank, it took 38l to fill it, whats the formula?? 598/ 38= 15.74km/l I then took 100km/15.74 and got 6.35

so if this is correct I got/used 6.35l per 100km, which is close to sticker epa ratings..

[Idjiit]

Heh, I think mine are set ridiculously high right now because I didn't let air out after the rallycross I cranked them up for. :O

[Tankota]

Yes you might get some better milage by increasing your tire pressure above the factory recomended settings - but remember you will also increase uneven wear (the centers will wear out before the edges) your braking will be reduced and your corner grip will be reduced - plus the harshness of the ride will be increased... all cause by overinflating the tires.

The numbers on the door are a result of lots of testing with that size tire on that excact style of car - it's the pressure that gives you the best milage along with the best contact patch of rubber on the ground that size tire for that car. Reduce that, and you get less milage, more wear on the edges, and slop and roll on curves. Increase it, yes you might get some milage, but less rubber and control on the ground, harsh ride, and wears the middle. So keep that in mind.. Oh yeah, drive a car with tires inflated to the max in rain? That's just asking for loss of traction in either braking or corning, and even hydroplaning. Those numbers are not just random that they post on the door.

As for the max tire pressure listed on the tire? It's just that, it's the max the tire should ever be inflated under any condtions, it's what it's tested to at the rated speed. Go over that or the speed rating and the tire could fail is what they are saying. Just because your engine is rated for 6500 RPM max before redline does not mean you should drive it there all the time. The most I'd go over the door sticker is 5psi, that might gain you some milage but still have a good contact patch. You can also increase it if you have a heavy load in the car. And it usualy is correct, the front will be higher than the rear due to the engine weight, but if so the door sticker will list a higher number for the front than the rears. Toyota has already paid engineers the money to figure out the correct tire pressure for the car, why go around guessing on your own?

There is some tests you can do to find the right pressure for a modified vehical, I do this all the time with modfied trucks with oversized tires for street use, but the point is on a factory Yaris with the factory sized tires it's all been done for you by experts, listen to it.

[Ziv]

Originally Posted by Tankota

Yes you might get some better milage by increasing your tire pressure above the factory recomended settings - but remember you will also increase uneven wear (the centers will wear out before the edges) your braking will be reduced and your corner grip will be reduced - plus the harshness of the ride will be increased... all cause by overinflating the tires.

The numbers on the door are a result of lots of testing with that size tire on that excact style of car - it's the pressure that gives you the best milage along with the best contact patch of rubber on the ground that size tire for that car. Reduce that, and you get less milage, more wear on the edges, and slop and roll on curves. Increase it, yes you might get some milage, but less rubber and control on the ground, harsh ride, and wears the middle. So keep that in mind.. Oh yeah, drive a car with tires inflated to the max in rain? That's just asking for loss of traction in either braking or corning, and even hydroplaning. Those numbers are not just random that they post on the door.

As for the max tire pressure listed on the tire? It's just that, it's the max the tire should ever be inflated under any condtions, it's what it's tested to at the rated speed. Go over that or the speed rating and the tire could fail is what they are saying. Just because your engine is rated for 6500 RPM max before redline does not mean you should drive it there all the time. The most I'd go over the door sticker is 5psi, that might gain you some milage but still have a good contact patch. You can also increase it if you have a heavy load in the car. And it usualy is correct, the front will be higher than the rear due to the engine weight, but if so the door sticker will list a higher number for the front than the rears. Toyota has already paid engineers the money to figure out the correct tire pressure for the car, why go around guessing on your own?

There is some tests you can do to find the right pressure for a modified vehical, I do this all the time with modfied trucks with oversized tires for street use, but the point is on a factory Yaris with the factory sized tires it's all been done for you by experts, listen to it.

Thank you very much for the detailed info. It's not like I am guessing what would be best for tire pressure to ensure best milage. I just think it would be nice for those of us who share the same car with their own opinion of what they think would be better. Afterall, this is the first car I truly brought myself. I would go anything close to factory made anyways, i think, unless I know more about it, I wouldn't go crazy and pump 10psi over. hehe

[why?]

Originally Posted by Tankota

Yes you might get some better milage by increasing your tire pressure above the factory recomended settings - but remember you will also increase uneven wear (the centers will wear out before the edges) your braking will be reduced and your corner grip will be reduced - plus the harshness of the ride will be increased... all cause by overinflating the tires.

The numbers on the door are a result of lots of testing with that size tire on that excact style of car - it's the pressure that gives you the best milage along with the best contact patch of rubber on the ground that size tire for that car. Reduce that, and you get less milage, more wear on the edges, and slop and roll on curves. Increase it, yes you might get some milage, but less rubber and control on the ground, harsh ride, and wears the middle. So keep that in mind.. Oh yeah, drive a car with tires inflated to the max in rain? That's just asking for loss of traction in either braking or corning, and even hydroplaning. Those numbers are not just random that they post on the door.

As for the max tire pressure listed on the tire? It's just that, it's the max the tire should ever be inflated under any condtions, it's what it's tested to at the rated speed. Go over that or the speed rating and the tire could fail is what they are saying. Just because your engine is rated for 6500 RPM max before redline does not mean you should drive it there all the time. The most I'd go over the door sticker is 5psi, that might gain you some milage but still have a good contact patch. You can also increase it if you have a heavy load in the car. And it usualy is correct, the front will be higher than the rear due to the engine weight, but if so the door sticker will list a higher number for the front than the rears. Toyota has already paid engineers the money to figure out the correct tire pressure for the car, why go around guessing on your own?

There is some tests you can do to find the right pressure for a modified vehical, I do this all the time with modfied trucks with oversized tires for street use, but the point is on a factory Yaris with the factory sized tires it's all been done for you by experts, listen to it.

Toyota engineers are recommending settings for 1 thing only - safety. They have to assume everyone that drives the car shouldn't really have a license, so they have to make all settings super-conservative so that the morons don't kill themselves and Toyota doesn't get sued.

No one ever recommended over-inflating tires.

Tire manufacturers know more about their tires than Toyota does. They know what is safe, and what the tires will handle.

Using the maximum pressure of a tire will not cause uneven tire wear as the manufacturers have created the tires to run at that setting.

It is always best to trust the manufacturers of a component over the manufacturer of the entire car.

[Idjiit]

Originally Posted by why?

Using the maximum pressure of a tire will not cause uneven tire wear as the manufacturers have created the tires to run at that setting.

It is always best to trust the manufacturers of a component over the manufacturer of the entire car.

This really isn't true. Tires don't exist purely outside the context of the car they're attached to. The performance characteristics of the same tire attached to a 2,000lb car vs. a 4,000 lb car are going to be different. You cannot simply say "the max tire pressure is 44lbs, so that's what I'm going to use". It just doesn't work like that.

[foober]

another thing to take into account. Is the gas stations you fill at. I just filled half my tank and found I am now only getting 36 miles to the gallon. My last three half fillups came out to 40 miles to the gallon at another gas station. Then I went to this other gas station and wound up after the calculations of getting the 36 miles to the gallon. Could it be that gas station meters out gas differently.

[Idjiit]

Originally Posted by foober

another thing to take into account. Is the gas stations you fill at. I just filled half my tank and found I am now only getting 36 miles to the gallon. My last three half fillups came out to 40 miles to the gallon at another gas station. Then I went to this other gas station and wound up after the calculations of getting the 36 miles to the gallon. Could it be that gas station meters out gas differently.

Yes, this is the fundamental flaw in the self-calculation method. Depending on the pump, how far you have it stuck in, etc. the amount of gas dispensed on a fill up can vary.

[nwdixieboy]

I got 42.5 MPG in pure highway mileage. I live in Seattle with lots of hills and get anywhere from 25 to 32 in mostly city driving.

[stuffy]

the best i have acheived is 40 mpg on average, and that is driving very easy 50/50 highway/city, tire pressure is checked every 2 weeks

i don't understand how some can get better mileage in the city, driving hard,

are some of us not doing the math properly or can there be that much variation with the same car?

[spellcheck]

Thought I'd add this report:
Yaris sedan - automatic
For a 166 mile stretch of highway (I86 through New York State, so quite hilly), I used 3.76 gallons, which is about:

44.1 mpg
(or 5.32L per 100km).

Most of it was at 70mph except for a 20 mile stretch of construction at 50mph. I had the air conditioner on for only a couple of minutes. The trunk was full.

I'm pretty impressed by this little car (assuming I calculated everything correctly, and the trip meter and gas pumps were all functioning properly). I'll have to measure it again on my next trip and see if it compares.

[punch]

Originally Posted by spellcheck

Thought I'd add this report:
Yaris sedan - automatic
For a 166 mile stretch of highway (I86 through New York State, so quite hilly), I used 3.76 gallons, which is about:

44.1 mpg
(or 5.32L per 100km).

Most of it was at 70mph except for a 20 mile stretch of construction at 50mph. I had the air conditioner on for only a couple of minutes. The trunk was full.

I'm pretty impressed by this little car (assuming I calculated everything correctly, and the trip meter and gas pumps were all functioning properly). I'll have to measure it again on my next trip and see if it compares.

wow thats almost better then the listed epa ratings...

[stuffy]

nicknicknick, are you sure you are calculating properly? i can't see this car getting anywhere near 54 mpg, that is what many report the prius hybrid as getting

[Ziv]

You guys got some ridiculus numbers. When is it going to be MY TURN!

[punch]

Originally Posted by Ziv

You guys got some ridiculus numbers. When is it going to be MY TURN!

well in my case it was the first tank, I drove slow, never going above 130km/hr

on my current/secound tank, i'm just driving normal without looking at the gas uasage, and i can see its burning it faster, but i also have driven at 140 too...

will post the results of my secound tank when it runs empty..

[NickNickNick]

My last highway trip I drove 710kms on 38-39 litres.

My last city fill was 31L on 478kms.

I will say that I live in Saskatchewan, and there are virtually NO hills at all, though the highways are crappy enough that there is a lot of slowing and accelerating on the highway.