Wondering why people complain that Yaris' cant get good mileage?!

[bkrownd]

Originally Posted by jhsouders

I actually find that i get better mpg on hilly terrain, granted its still highway. Going down the hills i just throw it in neutral getting around 4-5 hundred mpg while maintaining speed (DFCO would slow my car, and i would again have to use gas, so neutral is better in this case).

I've always suspected I get better MPG going up and down shallow mountain slopes than I would cruising at constant speed on flat ground. More energy is wasted turning the motor at cruising RPM than at idling RPM, so storing energy as elevation gain on the uphill climb and coasting or engine braking most of the way back down should yield higher MPG than cruising at high RPM on flat ground. Even despite the extra energy used to climb and the thinner air at higher elevations.

Just make absolutely sure that you're in a car that WILL NOT STALL while coasting. My stickshift Toyotas will idle happily until The End Of Time, but I've encountered some SUV type cars with automatic transmissions that will not idle reliably and are not safe to coast.

[sailbob]

Originally Posted by Zaphod

Stop and go can really hurt your mileage. When I'm doing city driving, I do a lot of compression braking (manual transmission), I time the lights and maintain constant speeds wherever possible. Engine braking with your foot off of the gas shuts off fuel completely so it's even better than idling in neutral! Of course knowing that, you can start off with more of your friction brake earlier to stay in compression braking for longer ;)

When you think about it, if you just reduce the number of times you even need to accelerate, it's even better than accelerating slowly. Very few people drive like that, if you're like the other 90% out there you just follow nose to bumper, mimicking the car in front of you with very little space or time to do anything different.

So knowing that, you should always be paying enough attention to what's going on in front of you to know when you need to start gliding in neutral to slow down, or when you need to start engine braking, always keeping things as smooth as possible for any cars behind you. As a rule of thumb, one should very very rarely need to use friction brakes on the highway. Thinking ahead, paying attention and driving more proactively is the key here, which is actually safer then following bumper to bumper and reacting.

You have to remember that your mileage really starts to drop off after 55, so I like to keep it between 50 and 60, in fact when there's no traffic behind me, I like to make it a point to allow the car to drop to 50 at the crest of a hill, and speed up no faster than 60 at the bottom, making small adjustments to that accelerator pedal where necessary. If there are downhill slopes that allow me to maintain the speed limit at 60 in neutral, I'll do it. And of course I'll use less gas on hills approaching areas where I know I can actually gain speed in neutral. And of course I'll even throw it in 5th gear and use DFCO when I know it will maintain it's speed, essentially using no fuel at all and holding the speed limit.

For me the real limiting factor for my fuel efficiency is that my trips are usually too short to allow the engine warm up enough. Heck, if you're mostly doing short trips like me and you do a lot of city driving you might be right on.

It's really all up to the individual and their driving conditions, but I can tell you from 1st hand experience it's very easy to achieve 50mpg on long trips if you can manage to keep the speed down.

The ScanGuage supports your statement exactly. If I keep the speed down under 45 on level ground with little stop and go (country road) I can actually obtain a little over 60 mpg. However accelerating to 70 and no regard for pedal control mileage drops to 32 to 35 and with an opposing wind 28 mpg. The a/c drops it another 10 mpg.

[DevilGirl]

Originally Posted by bkrownd

Some of you peeps need to leave your Road Raging areas and find saner corners of the country to live in.

I really hated it when some of the roads went to 75. Never drove faster than 65 max on those, and never will. As a passenger I was in a car that hit a deer at 75 in heavy traffic, and we escaped death by mere inches. Once was enough...

Actually I do live in a relatively sane area. It's just the commute to work, since I do live "in the country" as opposed to the city where the work is...

[STC]

Originally Posted by DevilGirl

Actually I do live in a relatively sane area. It's just the commute to work, since I do live "in the country" as opposed to the city where the work is...

Yeppers! Sane here... You know how State College area is! When they call for "rush hour" it's more like 'rush minute".

Cheers!

[daf62757]

You know, the difference between 41 and 38 MPG is not really that much. The creature comfort of cruise control and AC make it well worth the 3 or 4 MPG that these luxuries cost me.

[Chuck G]

Originally Posted by daf62757

You know, the difference between 41 and 38 MPG is not really that much. The creature comfort of cruise control and AC make it well worth the 3 or 4 MPG that these luxuries cost me.

[Yaris Hilton]

Yeah, I've said the same thing. I'm using them and taking what I get. I drive reasonably, but I don't do real "hypermiling."

[bkrownd]

Originally Posted by daf62757

You know, the difference between 41 and 38 MPG is not really that much. The creature comfort of cruise control and AC make it well worth the 3 or 4 MPG that these luxuries cost me.

YMMV. I will get out and push for 3 extra MPG. ;)

[gokartride]

AC isn't really a creature comfort here...it's life support!

[Kal-El]

I'd still run my AC even if it dropped FE by 25%.

If the cabin temp is above about 72 degrees, I run the AC.

[Yarisduder]

So what was said above is that if on my two best tanks I hadn't run the AC I'd have gotten about 50mpg? How much energy does it really require to run the AC? 1hp? 2hp? I doubt more than that, so I should probably see a mere 1 to 2% increase in fuel mileage if I turn it off. Thinking back though, my best mileage is with the air conditioner turned on, maybe it's because the fuel atomizes better in hotter weather? Maybe it's because I changed the engine air filter? It certainly has nothing to do with the AC.

Does the Yaris require the full power of it's engine to keep moving? Is it possible that the AC operates on extra power that would otherwise be wasted and therefore only affects your fuel efficiency when accelerating or driving very very fast?

[yarrr]

Originally Posted by Yarisduder

So what was said above is that if on my two best tanks I hadn't run the AC I'd have gotten about 50mpg? How much energy does it really require to run the AC? 1hp? 2hp? I doubt more than that, so I should probably see a mere 1 to 2% increase in fuel mileage if I turn it off. Thinking back though, my best mileage is with the air conditioner turned on, maybe it's because the fuel atomizes better in hotter weather? Maybe it's because I changed the engine air filter? It certainly has nothing to do with the AC.

Does the Yaris require the full power of it's engine to keep moving? Is it possible that the AC operates on extra power that would otherwise be wasted and therefore only affects your fuel efficiency when accelerating or driving very very fast?

On the freeway, having windows down creates drag which hurts your FE than having the A/C on.

And no, the A/C doesn't run on magical "extra energy." Just about every ounce of wasted energy has been engineered out of modern highly fuel efficient cars.

[Yarisduder]

I never drive with the windows open, and except for the last two tanks of gas because of a road trip all my driving is city driving.

[Yaris Hilton]

Probably around 35 MPH is a break even point between having the windows open and having AC on. Above that I always close the windows and use the AC as needed. Window drag varies a great deal with the wind conditions, of course. Once I've spent the energy to cool off a hot interior with the AC, I'm unlikely to roll the windows back down. Keeping the AC on low recirculating doesn't take a lot of power.

[BailOut]

Originally Posted by yarrr

On the freeway, having windows down creates drag which hurts your FE than having the A/C on.

This is inaccurate. In both testing with our SGII's and as proven in the 3rd season of the Mythbusters television show, windows down is always more efficient than a/c at any speed.

In fact, with the SGII it is nigh impossible to read the drag hit of having the windows down, but turning on the a/c at any speed is an instant large and sustained hit to FE.

[daf62757]

Originally Posted by BailOut

This is inaccurate. In both testing with our SGII's and as proven in the 3rd season of the Mythbusters television show, windows down is always more efficient than a/c at any speed.

In fact, with the SGII it is nigh impossible to read the drag hit of having the windows down, but turning on the a/c at any speed is an instant large and sustained hit to FE.

I didn't see that episode, but I did a search on found this website.

http://green.autoblog.com/2007/08/29...-down-episode/

According to the website, windows down does hurt mileage. Just on a simple physics level, the air entering the cabin has to have some breaking action on the vehicle as the air has no place to displace. If you had the tail open, it could be a flow through action that might not effect the velocity of the car.

I am no expert on the matter....but I did stay at a Holiday Inn Express last night and will use my AC....because I love cold air and I am rich enough to afford the extra quarter.

[Yarisduder]

Originally Posted by BailOut

In fact, with the SGII it is nigh impossible to read the drag hit of having the windows down, but turning on the a/c at any speed is an instant large and sustained hit to FE.

Do you have numbers to share with us? How did you control your environment? Was the ground flat? What speeds, was there wind, etc?


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[BailOut]

Originally Posted by Yarisduder

Do you have numbers to share with us? How did you control your environment? Was the ground flat? What speeds, was there wind, etc?

There was a big thread on it that was lost in the hack, but as I said the Mythbusters found the same thing, as did the folks on CleanMPG, as did the folks on PriusChat, etc. In other words it has become common knowledge.

As for the test environment, etc., it simply doesn't matter. Windows down in any scenario is far, far more efficient than using a/c in any scenario. It doesn't matter if you're pulling into your driveway or cruising down a highway, rain or shine, winds or no.

Tinting goes a long way for avoiding a/c use. When combined with window vents it lets me keep the 35% front window on the sunny side cracked about 2 inches and have the shaded window fully down, or both windows down when the sun is directly overhead or to the front. Aided by the 6% tint on the rear windows and top of the windshield (the darkest allowed by local laws) it helps keep the interior much cooler than without any of these things. In stifling heat I run the fan (just the fan - no a/c) on the fresh intake setting to aid with circulation.

Despite living in a high desert region the only times I have ever run the a/c is when my wife experiences hormonal issues. None of my other passengers ever ask for it.