Fuel Efficiency and the Yaris

[KrazyDawg]

Originally Posted by BailOut

You're off to a great start, Rikster! You should be able to stomp on us folks in the U.S. that can only get the 1.5L.



Hi, KrazyDawg. Using the SGII many of us have verified that 35-45 MPH is the sweet spot for efficiency on relatively flat roads. The 10 MPH difference is a broad range that depends on many factors such as tire pressure, road quality, wind resistance, ambient temperature, etc., but the common sweet spot within that range seems to be between 37-39 MPH.

Thanks Bailout. There's been a few occasions where someone drives at 40 MPH on the 50 MPH strech and I usually go around because I thought the sweet spot was around 50-55.

[Rikster]

Originally Posted by BailOut

You're off to a great start, Rikster! You should be able to stomp on us folks in the U.S. that can only get the 1.5L.



Hi, KrazyDawg. Using the SGII many of us have verified that 35-45 MPH is the sweet spot for efficiency on relatively flat roads. The 10 MPH difference is a broad range that depends on many factors such as tire pressure, road quality, wind resistance, ambient temperature, etc., but the common sweet spot within that range seems to be between 37-39 MPH.

Well it's not really fair, holland's landscape is all flat :D which come's in handy when it come's to fuel efficiency!

[Falconia]

Originally Posted by BailOut

You're off to a great start, Rikster! You should be able to stomp on us folks in the U.S. that can only get the 1.5L.



Hi, KrazyDawg. Using the SGII many of us have verified that 35-45 MPH is the sweet spot for efficiency on relatively flat roads. The 10 MPH difference is a broad range that depends on many factors such as tire pressure, road quality, wind resistance, ambient temperature, etc., but the common sweet spot within that range seems to be between 37-39 MPH.

You mean the real speed or the speed that speedometer shows. I just checked with navigation system that speedometer shows 4,4mph above real speed

[KrazyDawg]

What's the optimum speed for driving on say a flat road? Would it be 55 MPH? Less? If anyone has a scangauge, I would be interested in the numbers. I have a 6-7 mile section in my commute where the speed limit is 50 MPH but there are stop lights.

[Yaris Hilton]

Originally Posted by KrazyDawg

What's the optimum speed for driving on say a flat road? Would it be 55 MPH? Less? If anyone has a scangauge, I would be interested in the numbers. I have a 6-7 mile section in my commute where the speed limit is 50 MPH but there are stop lights.

For most cars under steady state, level ground conditions, maximum mileage is found in the vicinity of 35 MPH.

[Kal-El]

Originally Posted by KrazyDawg

What's the optimum speed for driving on say a flat road? Would it be 55 MPH? Less? If anyone has a scangauge, I would be interested in the numbers. I have a 6-7 mile section in my commute where the speed limit is 50 MPH but there are stop lights.

And that's unfortunately where we waste most of our gas - every time we have to stop. Getting back up to speed is the killer.

I'd estimate that the Yaris achieves between 45-55 mpg if it is kept very steadily at 40 mph on a level road with no head wind.

[sickpuppy1]

Well I cant gripe! Just got my 2010 Yaris sedan last Saturday, filled up by the dealer, so not sure how well it was done. Anyways, I have a tendancy to "top it off" , but I filled it slowly and checked at the 1st click. 10.2 gallons,lol pretty low. 40.9 mpg for 418 miles .When topped off at 10.8 gallons its 38.7 mpg. Not bad for the first tank. That 418 miles is total on the car, so were a couple of thousand away from broke in. And to be honest, not being used to the car and not using the cruise much, I've found myself between 75 and 80mph at times. Anyways, lovin it so far!! I'm gonna bump the tire pressure a bit and see how I like it. I'm not gonna go the hyper miler route, but will adjust driving to a certain extent to help. I owned a 2001 Civic before this and routinely got 36-38 with it.

[talnlnky]

Originally Posted by sickpuppy1

I'm not gonna go the hyper miler route, but will adjust driving to a certain extent to help. I owned a 2001 Civic before this and routinely got 36-38 with it.

hahaha hahahaha.... yes you will, just wait 3-6 months, after what... 2 weeks you are already tracking fuel efficiency and posting about it... HYPERMILER HERE YOU COME!

[Ranger SVO]

So far I'm very happy with my Yaris. Last week I drove 218 miles and put in 5.52 gallons of gas. Thats about 39.5 miles per gallon. In my opinion, thats really good.

About 80% of my driving is highway, the rest city. Awesome little car

[Hypermiler]

I am using a ScanGauge II to help me get the most out of a gallon of gas. Since I got it, I have been monitoring the ScanGauge II and have been able to manage a new best of 47.5mpg. That was the fuel economy average for a ride home from work, a 34 mile drive. It is flat, speed limit if 50mph, and only a few stops... Ideal for generating great mileage numbers.

But 47.5mpg is in Prius and the econobox diesel range - AWESOME for a $15k car!!!

[BailOut]

^^ Well done!

[pawsplus]

Got 40 mpg on my second tank!! I drive mostly on state roads/back roads. Not too many stop signs but lots of hills and turns and slowing down and speeding up. Some in the city. Wasn't on the interstate at ALL during this tank!

[Boost Addicted]

''2) Accelerate and brake slowly and steadily, avoiding jackrabbit starts and stops. No one ever got a trophy for getting to the next red light first or getting up to highway speed in the first 200m of an on-ramp, and you can't beat the timing of a stop sign. In the Yaris I try to never let my RPM get above 2,000 unless I need to merge quickly, in which case I allow for 2,200. The only time I get higher than that is on the climbing side of my mountain commute, as once you get into 6% and 7% grades it simply requires more fuel to keep moving.''

Shifting and accelerating at such low RPM's is actually very hard on the transmission and engine.... We've had multiple cars in the shop with tranny problems because people are afraid of RPM's.

It is fact that MPG, at a X miles per hour, is un-affected by RPM's. You could be at 2K or 5K, at X speed, you're getting the same fuel mileage. The difference is engine and transmission load.

And trying to accelerate from lower RPM's puts a huge load on the engine, and actually uses much more fuel than if you accelerate from 3000 RPM's. Think of it like riding a mountain bike. Does it take more energy to get to 10mph in the highest gear, peddling slowly (due to the force it takes), or in the lowest gear at a faster rate, with great ease?

Trust me on this one lol, do NOT be afraid of RPM's, it doesn't affect fuel mileage in the terms stated above. Do your engine and tranny a favor by shifting at 3K or even a bit higher. I'm rarely cruising below 2 grand... And I get great fuel mileage.

Not tryin' to stir up arguments here, just letting you guys know what I've learned throughout the years of going to school for this as well as field work.

=)

[Boost Addicted]

'10) and never idle it to warm it up. The Yaris offers a low coolant indicator light in the dash panel that let's you know when it is running in its least fuel efficient state. As for idling to warm it up, remember that you're getting exactly ZERO MPG while idling.''


I also have to disagree with this lol. As you DO get zero mpg while warming up, you're getting worse fuel mileage driving it cold, especially in the winter... In the summer, not so much.

But in the winter, metal shrinks even more with the colder weather, and your tolerances are loose (eg. piston rings, oil pump gears, valvetrain) making operation sloppy, inefficient, and less resistance to wear. In addition, the coolant temp sensor will dump a bunch of extra fuel until the engine is at its operating temperature... So even though you're running rich at idle to warm it up, you're still using more fuel when driving it cold...

Ofcourse, when you measure lost MPG's when letting it warm up at idle, vs driving it right off the bat, numbers will be lower... But if you calculate volume of fuel used to warm the vehicle at idle vs. volume of fuel used to warm it driving when its cold, idle will get better mileage every time.

In summer weather its really not necessary.. But regardless of ambient temperature, you shouldn't put the car in gear untill 10 seconds after ignition to allow for oil to properly lubricate all parts of your engine

Just my .02 :)

[sbergman27]

Originally Posted by Boost Addicted

I also have to disagree with this lol. As you DO get zero mpg while warming up, you're getting worse fuel mileage driving it cold, especially in the winter... In the summer, not so much.

This very interesting topic is one which calls for a great deal of quantitative testing. It can't be discussed in coarse terms like "driving vs not driving" or "winter vs summer". Obviously, putting it in drive and letting the idle speed pull you toward the edge of the parking lot is going to get you better FE than just sitting there idling. On the other hand, turning the key and tooling out onto the 70 MPH Interstate is going to be worse than just sitting there at idle for a while. The truth lies in the minute details of the specific situation.

Intuitively, I would say that if it is practicable to drive very slowly and leisurely until the "Cool" light goes off (which happens at about 128F coolant temperature, BTW) then that is probably the best thing to do. I you must push the engine hard from your cold start position, then it may be best to warm it up a bit. This is not a question with a simple answer. And I'm not Aristotle. So I won't claim to have an answer based upon pure logic and reason.

We need some experimental data to sort this one out.

-Steve

[Boost Addicted]

Honestly I don't feel the truth lies in minute details of the situation... But none the less, the huge factor of increased engine wear is at play. And mileage doesn't matter too much when you have worn piston rings at 150K.

And this isn't based on ''pure logic and reason'', its based on fuel mileage calculation.

[sbergman27]

Originally Posted by Boost Addicted

Honestly I don't feel the truth lies in minute details of the situation... But none the less, the huge factor of increased engine wear is at play.

That is a different, but valid, vector, which I was not addressing. But I would say that it actually *increases* the complexity of the question. I would agree that including that metric would shift things a bit toward delaying, or slowing down the allowed driving speed.

Consider that you are going to get more miles out of the engine if you start it and let it idle in drive, at whatever speed that gets you, and if conditions allow, than if you just sit there getting 0 miles per revolution out of it.

Actual data *is* needed to map this landscape.

-Steve

[Boost Addicted]

Meh ::shrugs::, I'll drive how I drive and you guys can drive how you drive lol, I was just throwing in my .02

All I'm saying is, with the way I drive as specified above (this is for the Jetta, my girlfriend has the Yaris) I get 34mpg combined city highway... And I have about 275wtq. I'm not bragging about numbers, I think the Yaris is a very solid built car, everything feels tight, its comfortable, and its practical... I'm just saying that if its possible for a larger displacement engine with much more power to get as much fuel mileage as it does, you Yaris owners could benefit from the same techniques and practices I use to get the full potential out of your car.