Every now and then it’s nice to see something cool on the oil / environmental front — and this is cool.
A week ago, five drivers took a car to a little stretch of road in Pennsylvania. After a whole weekend of driving in four hour shifts, they had achieved fuel economy numbers that seem almost magical: 110 MPG.
So what was the secret? It wasn’t some miracle fuel additive, some secret engine design, or some low friction track. This was an ordinary car, running on ordinary roads, using ordinary gas. The answer lies in two things: a unique ability of the Toyota Prius, and good driving technique.
This wasn’t the first time these drivers had achieved extraordinary mileage. One of the drivers first posted about a 818 mile tank he had gotten over on PriusChat.com and challenged other drivers to beat him. Within a week, reports came in of a 900 mile tank. Then 967. Then the first driver edged 1000.
With that experience behind them, the best of these drivers teamed up for a experiment in pushing the Prius to its mileage limits. With a camera crew from HBO in pursuit, and lots of local media monitoring their progress, they set out on the Prius Marathon Run, hoping to get 1200 miles from one 12 gallon tank of gas.
For this run, they made only very slight changes to the car. They pumped up the tires to 60psi to cut rolling resistance. And they added some electronics. Only the electronics weren’t really to improve the mileage, they were just to monitor the mileage. The regular displays on the Prius only go up to 99.9 MPG, and these guys knew they were going to top that, at least for part of the trip, so they loaded in some aftermarket gear.
This thread in PriusChat details their progress, along with the comments of Prius fans (like yours truly) “watching” over the Internet as drivers came off their shifts and posted the results. For those of us tracking the progress, this thing was every bit as exciting as any NASCAR race. When the ‘add fuel’ warning began to flash around 1,000 miles, it seemed like the predicitions of 1100-1200 miles were going to be right on. But the car kept on going for almost nine hours with the add fuel blinking all the way, finally reaching 1,397 miles before the well ran dry (and only then because the exhausted drivers finally decided to try to waste some gas).
The Pittsburg Post-Gazette caught some of the MPG-fanatic action:
Over on AutoBlog scoffers stood by to pan the event as “not real world numbers,” but one of the drivers, Wayne Gerdes, had an answer for them:
For someone who has a Prius but “only” gets 52MPG, these guys have set a high bar. Excuse me while I practice my technique.
very cool, thanks for the inspiration. My next car will definitely be a Prius unless there’s something even better on the fossil fuel by that time.
Great post! What’s the technique? Is it something to do with switching from gas to electric?
Yeah, what’s the technique? I’m dying to know. The only link that didn’t time out on me was the last one and it referred “pulse and glide.”
Simply put, they tried to minimize use of the electric motor.
Sounds counter-intuitive, doesn’t it? But by accelerating at just the right rate, they kept the gas engine in its optimum band, while not engaging the electric motor and depleting the battery. Then, when topping a hill or coasting toward a stop sign, (okay, avert your eyes if you’re nervous about 50 year old traffic laws) they flicked the car into neutral. By coasting in neutral, the gas engine was thrown completely out of the loop, along with the electric motors. This made for a very low resistance, engine-off glide. Stop at the light, wait with engine off, flick it to drive and repeat.
In terms understandable only to those who have spent hours staring at the displays in the Prius, they tried to “turn off all the arrows.”
This doesn’t mean the electric motor is overkill. It’s vital in those low-speed crawls. If you’re trying to get on the Interstate from a short ramp, it applies a good kick in the pants. And it’s super keen for scaring the pee out of someone in a parking lot.
In slightly different driving conditions, the electric motor could have come into play much more often, but these guys mastered the art of using just enough gas to overcome rolling resistance, and milking every gentle hill along the route for the maximum return of potential energy.
There’s a hilly route that I can take from business to home. Usually I avoid it because the turns and hills choke down my MPG. But yesterday I gave it a run paying very careful attention to the “pulse and glide” technique and found I actually got better mileage than on my regular route.
Last night, I found myself using Google Earth to plot a proper “rolling” route for my next vacation. I think I can safely say that I’ve gone MPG nuts.
This sounds like how I used to drive my car when I was a “financially challenged” teenager. I had this hideous, green Vega for awhile. The thing also had an aluminum engine block, and it overheated all the time. I used to put it in neutral going downhill. It saved gas and moved up the coolant addition time considerably.
Also, reverse was broken. Fortunately, being apparently made of aluminum, the car was light enough that I could pull up at corners, get out, and push it backwards if I couldn’t find another parking space. One becomes much more “involved” in driving under such conditions.
I had no idea the Prius was so interactive — now I REALLY want one!
And that reminds me of when I was a teenager and my best friend’s older brother had an Austin-Healy sports car. She and I used to “borrow” it when he was away and to hide our use of it we’d drive it backwards, because the mileage indicator would actually click back. He must have wondered why he wasn’t getting better mileage. 🙂
me too
A Prius is a small car to start with. It would probably make 40 mpg or so with a conventional engine. But, the downside of a conventional engine is that some gears are more fuel efficient than others. The low gears are particularly fuel inefficient as is idling time. A hybrid electic runs a smaller engine but keeps it continually at its “sweet spot” using battery boosts in places where a conventional engine would be less efficient like going from 0-20mph. Also, hybrids don’t idle, so they don’t use fuel when they are at a stop, and they have regenerative braking which uses the energy removed from the wheels in braking to recharge the batteries. Combine all these features and you have a highly efficient system.
By the way, electric hybrids are not stunningly new technology. Diesel-electric hybrids have been the norm in railroad engines for decades.
Actually, the current Prius is a “midsize,” about the same length and interior capacity of many American sedans. But you’re dead right about the key here being engine efficiency.
What these guys were able to do was train themselves to keep the engine in the most efficient band when accelerating, and then glide downhill. The real difference they took advantage of was that, below 41 MPH, when coasting, the Prius engine is completely out of the loop — not just turned off, but completely disengaged. The low resistance glide, followed by an optimum “pulse” was the key. The electric motor of the Prius played into it only in those “below 20” crawls where they were able to move stoplight to stoplight on electric without engaging the conventional engine.
There’s a feedback screen in the Prius that displays fuel use in five minute increments (a kind of crawling bar chart) along with the current consumption rate. By watching it carefully (always with one eye on the road, of course) it’s possible to see that going slightly faster or slower in different conditions can make a big difference in fuel economy. My wife calls our Prius my “moving video game.”
Or, as she said when we left the dealer, “Well, that’s the biggest gadget you’ve bought — so far.”
We just bought a Prius this morning–I was finally able to talk sngpapa into it after it cost him $43 to fill up the Odyssey over the weekend. We snapped up the last one on the lot and I’m still a little giddy about it. Thanks for the further inspiration!
Reminds me of a Seinfeld episode.
Number one way to save gas is to not be a speed demon. Slow down, especially you SUV drivers, ’cause ya’ll are the rudest of all.
get a VW TDI 2.0L and stick in that Prius and get about 5,000 MPG. Ok, kidding. But why not put a diesel engine in a hybrid so you can run it on biodiesel?
My understanding is that the diesel engines currently in cars are not suited to hybrids because they can’t be easily stopped and started over and over on the fly (though that could be auto company propaganda).
There’s been some work done out at UC Davis that indicates a small high speed deseil teamed with a larger electric motors and a big battery pack may be the optimal solution for a plug-in hybrid. All I know is that the first company to build a vehicle that can do 50 miles on a charge and which can then run long distance on fuel (E85 or bio-desiel, I hope) gets my money.
Heck, I’d be happy if someone came out with an E85 retro-fit kit for the Pruis.
I think VW did take a stab at it, and found that they didn’t gain much. My thinking is that you kind of need to start from the drawing board, and see what really makes sense. A diesel uses very little fuel at idle, so perhaps instead of stop/start of the engine, you just let it idle when you don’t need it.
Question for the Prius owners on no-lead gas vs. ethanol blends with regards to mileage.
My friend Art, has a Prius. We drove from Fargo to Minneapolis a couple months back. We left Fargo with a full tank of regular no-lead gas and average 50 mpg to MPLS, leaving MPLS, still 50 mpg, added 6.2 gal of ethanol blend at Clearwater, MN, and from then on the moving bar graph dropped to 38 mpg and never exceeded 40 mpg before arriving in Fargo. No headwind on return, and no other variables to consider. Art says it’s the same every time he makes the trip.
I have not noticed any mpg difference using ethanol with either my ’83 Chev auto, 74 Chevy pickup, or ’00 Outback, so with regards to the ethanol controversy in general I have no particular opinion.
But I am mighty curious as to the mpg difference on regular vs. ethanol. Got any clues???
Ethanol has about 65% as much BTU per gallon as gasoline. I normally drive with gas that’s 10% ethanol and get 50-52MPG (about 80% highway driving). That 10% ethanol should make for something like 3% difference in my mileage (say 4-5 MPG). Blends up to 15% should be well within the Prius range — and at that level you’d see maybe 5-7MPG less.
If your friend is using something like E85 (which I would love to use), the lower mileage is certainly understandable. However, it’s also not safe for the car. While the electronic oxygen sensor in the Pruis can likely adapt to the difference and keep the car running smoothly, Toyota has made it clear that the plastics in the Prius fuel line have not been approved for use with Ethanol.
Ethanol is a solvent, and highly corrosive to many plastics. The plastics in most cars are designed to take 1015% ethanol, but not more. Cars that are “multi-fuel” capable generally have metal fuel lines, special gaskets, etc. Heck, the Prius even has an expandable plastic “bladder” for a fuel tank. I’d hate to rot that guy through.
However, the moment someone offers a kit to fix up the Prius for E85, I’m all over it — even if my MPG numbers will go down.
Thanks for the informative reply. The Prius certainly has some fascinating technology.
My friend says that the Minnesota blend is 10% ethanol. So we still have a mystery as to why you are able to get the usual 50-52 mpg, and his drops to 38-40 after adding the half tank of ethanol/gas. And our trip was almost 100% highway miles. He says he has the same results every trip.
I think his model is 2003, so if yours is newer it could that the engine is tuned more specifically to a 10% blend.
There was a fun story over here:
http://www.greencarcongress.com/2005/08/solarpoweraugme.html
where someone attached some solar cells to the roof of a Prius. What would be cool is for someone to do this to a pluggable Prius such that the thing can recharge during the day when it is presumably sitting parked.