Question about MPG

Be surprised then because it does--unless you're on a hill and the force of gravity causes the car to keep from slowing down.

It can go a mile or two on battery alone. Quite often while driving under 42 MPH, you're driving solely on battery power.

Fuel economy is only part of the equation; the other part is cost of the fuel.

And those are considerations that are separate from pollution.

Sorry...

Sure.

With you so far.

The last two cars I've owned (one petrol / gasoline, one diesel) consume no fuel at all on the over-run (but I agree they are not conserving any energy while slowing down).

Yes, although a diesel engine consumes a remarkably small amount when idling compared with a gasoline engine, since it can run very much leaner.

I think it's fair to say that whether or not a gasoline / electric hybrid such as the Prius is "a better overall compromise of a design" depends on what kind of driving you mainly do. If you mainly drive in the city and spend a lot of time stopped at intersections, it makes good sense. Several European manufacturers make city cars with a stop-start system with a conventional engine. On a long steady journey with little opportunity to regenerate, the savings must be very slight, if any, compared with the same car without the 'hybrid' bit (but for the sake of argument still using the very efficient Atkinson-cycle engine and planetary transmission), and so under such conditions there's no reason why the car should be any better than a diesel, which was my original question.

Well made point, and all credit to them, and indeed to the far-sighted customers who care enough about all this to buy and run a Prius. Iadmire them, especially since I now understand that diesel isn't a viable alternative in much of the USA. However, as in my first post, I was really more interested in a straightforward user-based mpg comparison.

Thanks anyway,

Steve

Yes, I understand that.

...but surely, surely, you see that all that energy came from the gasoline engine in the first place, which was my point? Sure, in a conventional car slowing / braking energy is wasted, but even with a Prius there is no free lunch.

Oh, come on... ;-)

...and it all comes from the gasoline engine to start with! Look, all I'm trying to find out (as per my first post) is what mileage drivers such as you actually get per (US) gallon you put in the tank, as opposed to what Toyota's dash gauge (whether or not we agree it's a trip computer) tells you. I don't think the Prius "knows" how much gasoline you put in at any particular top-up, so the only reliable way (as the OP asked) is to keep a log and do the math yourself. Looking at the table at GreenHybrid.com it seems most drivers are relying on the dash indicator, "by display" in the jargon. You may say that "Frankly, both methods are so close as to render further discussion pointless" but I'd like to see some evidence to back that up. That's all. I've told you what I get in my European diesel car, but (unless I missed it) you haven't told me what you _really_ get in your Prius. All I get in this forum are explanations of how the Toyota system works - which I accept is very clever - but that's not my point. I'd be interested in a car that was truly as economical as claimed but not if (in fact) it's easy to get the same economy with a much cheaper diesel engine. I'm just trying to make a fair comparison, is all.

Steve

He meant that, when you're coasting, the motors/generators are taking energy from the wheels and putting it back into the battery. One does not have to be using the brakes to be regenerating.

It's a net savings because when the engine runs to recharge the battery it does so in its most efficient operating range, which produces much more power than is needed to run the A/C and other accessories. When the engine is off is obviously uses no fuel at all. Overall, even with the conversion losses, it's more fuel efficient to run the engine intermittently.

The beauty of Toyota's HSD system is that it can use a variable fraction of the engine's output with a direct mechanical connection, and allows sizing the engine to something much less than the maximum power requirement.

How many of these get equal or better fuel economy while meeting SULEV emissions requirements? Prius was designed more to minimize emissions than to minimize fuel consumption.

I understand that - but if you refer back, my initial question focussed merely on comparisons of fuel consumption, since we don't have the SULEV stuff in Europe (with a few exceptions, such as central London, where the Prius is exempt from the Congestion Charge).

Steve

Again, which vehicle are you comparing the Prius to? Until you compare EPA mileage figures, this is speculation.

Which user? I presume that would be you. We are back to my earlier suggestion that you rent a Prius to compare with the mystery vehicle to which you constantly allude.

Do you have any idea what a 30 mph wind does to mileage? Where I live, wind is the rule, not the exception.

I don't think the Prius "knows" how much gasoline you put in at any

I calculated my own mileage for the first few tanks. My calculated mileage was essentially the same at my displayed mileage plus or minus a couple of percentage points. My worst tank was 48 mpg. My best tank was 55 mpg. There. You have it.

To see what our EPA is contemplating, go here:

Too bad the same can't be said for a retarded fool like you, dick.

I have a four week old 2006. I get about 48 around town (suburban) and on the highway, but somewhat better in hilly rural terrain (up to 52). I noticed that others have experienced this as well. Tires are still at original setting. In a real city it drops to around 46.

I am trying to see if different brands of gas effect mileage. My latest tank of Getty seems to be doing better than the last tank (Shell). I am in upstate NY.

Mark

Michelle Ste> >

That is true, but gasoline isn't used at constant efficiency. Idling is 0% efficient and moving slowly is scarcely any better... worse as the engine displacement increases. Hybridization allows the very low efficiency modes to be replaced by electricity generated when the engine is developing power and getting much better efficiency. In combination with allowing downsizing of the engine (the electric side determines the acceleration) that accounts for the tremendous increase in in-town efficiency and modest increase in open road efficiency of hybrids.

Mike

In the old days the slightest downward movement of the gas peddle caused the fuel injector to squirt extra raw fuel. I remember experimenting with disconnecting it. There would be a momentary bog down as I tried to rev the engine. With the hybrid the fuel accelerator is replaced by a momentary boost from the electric motor. Another fuel savings is from the lack of a mechanical linkage between accelerator peddle and engine.

The electric motor provides for an extended coasting (to a red light for example) that if it weren't for the motor the car would come to a halt very short of reaching the light. With a traditional power train anticipating a red light up ahead by letting up on the gas peddle saves almost nothing. Actually, it rather comical to watch people zoom right up to a light when they knew it was red maybe 500 feet back or more.

Hybrids aren't for everyone. I dare say they are more suited for those of us who need not show our emotions by the way we drive. You can't rev the engine. You can't pass another car and make a lot of noise. These things don't cut it in the Animal Kingdom where growling and snarling cars helps people let off steam. So I guess if I have something to say, I step out of the car. Amazing how the other driver's safe heaven now becomes their prison while I lean on their hood and ask, " Do you have a problem?" Last time I did that (guy was flashing his high beams on a 35 mph road) he nearly crapped his pants. He denied flashing his lights.

There is one other Prius operational mode not yet discussed called Electric Vehicle (EV) or "stealth mode." At speeds below 42 mph, the vehicle can operate on just the electric motor with the engine off. The distance increases significantly at speeds below 30 mph. For example, the last 1-2 miles into work or returning home, I take streets with

25-30 mph limits. This last mile is run with almost no gas consumption unless I have to react to other traffic. This includes 2-4 m. rises, which can be taken at 10 mph without the engine.

This EV mode is a unique to the stock Toyota and Ford hybrid systems. Some models of Prius in Europe and Japan come with the EV button and in the USA, there is an after market kit to fit an EV button. So, are any other vehicles able to climb 2-4 m. without turning on the engine?

My 03 Prius has one well documented EV mode, reverse. In fact, even cold, the engine can not run when I back out of my driveway. The reason has to do with the planetary gears and engine. I can also climb steep hills in reverse.

It is possible to use the EV capability to considerably extend the "glide" part of "pulse and glide" driving. What this means is the speed decay is countered by the EV so the hybrid vehicle 'glides' further than an engine-off non-hybrid. For example, two vehicles starting at 40 mph start a glide down to 30 mph. The non-hybrid will go about 1/2 mile before reaching 30 mph and having to start the engine to speed back to

40 mph. The hybrid vehicle can stretch that energy-off glide to nearly a mile using a small amount of electrical power. The pulse back to 40 mph quickly add that energy back and you're back in glide again. But in the meanwhile, the hybrid has gone a considerably further distance.

Hybrids are also designed for frequent engine off and on operation. This means the start-engine fuel burn is extremely low and efficient. There is no Bendix gear that has to reach out and engaged the flywheel but effectively a directly connected motor that engages electronicly. This minimizes starting friction losses and engine wear. Unlike traditional

12 VDC starter motors drawing a hundred or more amps, the hybrid motors are 200-270 VAC motors drawing a few tens of amps. This lower current minimizes the resistance losses and heat suffered by ordinary starter motors.

Bob Wilson

Actually quite a few. One of the problems with an idling engine is the drop in exhaust gas temperature cools the catalytic converter. When the catalytic converter gets too cool, it doesn't work.

By turning off the engine, the catalytic converter remains at operational temperatures, it isn't cooled by idling exhaust gas. This keeps the emissions low.

Bob Wilson

Couldn't this be fixed with gas pedal controlled sound effects switch-selectable between, say, Hog, Mac, & Titanic? :-)

On average, what is the difference between your mpg calculated by the car's computer and by the gas station fill-up method?

499 responses: Choices Votes % computer 5mpg or more higher 17 3 computer 4mpg higher 38 7 computer 3mpg higher 70 14 computer 2mpg higher 107 21 computer 1mpg higher 12 2 both methods about the same 128 25 computer 1mpg lower 5 1 computer 2mpg lower 9 1 computer 3mpg lower 15 3 computer 4mpg lower 4 0 computer 5mpg or more lower 6 1 varies too much to give meaningful average 88 17

The only fair comparison is between similar-sized vehicles, using a standardized test, such as offered by various governments.

And it's not what is "claimed" - the manufacturers are required by law to post the fuel economy results of the governmental tests and no other figures.

post from Toyota GB press relations:

Prius Fuel Economy: Explaining the EPA Ratings Toyota explains what the EPA ratings actually mean, and lists ways to improve your MPG 79 Prius Fuel Economy Factsheet:

For comparisons: US:

US 2006 best mid-sized cars: Toyota Prius (Hybrid), 4 cyl, 1.5 L, Automatic(Variable), Regulargasoline, 60 US MPG city, 51 US MPG highway2: Hyundai Elantra, 4 cyl, 2 L, Manual(5), Regular gasoline, 27 US MPGcity, 34 US MPG highway Canada 2006 best mid-sized cars: TOYOTA PRIUS (HYBRID), regular gasoline, 4.0 l/100km (71 imp MPG)city, 4.2 l/100km (67 imp MPG) highway2: MERCEDES-BENZ E320 CDI TURBO, diesel, 8.9 l/100km (32 imp MPG) city,5.9 l/100km (48 imp MPG) highway Unfortunately, the UK site doesn't break out the size classes, but they will sort by fuel economy. The Prius is in the highest band of cars, in the 60-70 imp MPG range or 1-5 l/100km range, along with a bunch of tiny diesels.

Sorry to top-post but I just wanted to compliment you on your excellent, comprehensive reply to Steve's question. Scroll no further.

1: TOYOTA PRIUS (HYBRID), regular gasoline, 4.0 l/100km (71 imp MPG)> city, 4.2 l/100km (67 imp MPG) highway> 2: MERCEDES-BENZ E320 CDI TURBO, diesel, 8.9 l/100km (32 imp MPG) city,> 5.9 l/100km (48 imp MPG) highway>