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103 comments on Improving Mileage: "Hypermiling"
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103 comments on Improving Mileage: "Hypermiling"
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(source)
The ubiquitous tradeoff between time and energy....
At higher speeds:
(Source)
Interesting that everyone bows at the alter of the Prius, but both the VW and the Opel get better milage on this chart. All of the other tests that I have seen also place the VW TDI above the Prius in milage above 40 MPH.
I think if I could afford a new car I'd go for the VW TDI as it costs less, is much simpler to maintain (and probably cheaper?) and seems better suited to highway operation. Note: I live on a farm in a very rural area and spend 90+% of my driving at highway speeds.
As long as the current differential between petrol and diesel exists which is about 20%, the higher cost of diesel negates the increased mileage of the TDI. As a former mechanic, I would suggest you call the nearest VW service manager and ask what the cost of changing the timing belt on the OHC VW Beetle diesel which does need replacement every 100K or so. It is close to $1000. I do hope that we can get away from these attempts to prolong a POV transportation lifestyle and talk about a transport modality with a future and that will be electrified rail. We probably have 3 or 4 more years of relatively cheap oil until the supply demand curve really crashes and we need to start crushing our beloved Hummers and Excursions now to recycle the steel and start laying track ASAP!
http://www.atsltd.co.uk/
Jon
The Prius is realy optimised for city driving, It does have an Atkinson cycle engine which improves its cruising economy, The VW has the advantage of a more efficient diesel (due to the higher comp ratio) and the higher energy content of diesel. But for your application the VW is a better bet.
HTH
Neven
The advantage of the Prius is in city driving, where it's battery pack actually allows it to get higher mileage in the city than on the highway. That's the opposite from a standard ICE auto.
This graph is somewhat artificial in that people don't drive a constant speed from place to place.
That graph doesn't reflect my Prius experience at all. In good conditions, I usually get 55 to 60 mpg at 55 to 60 mph. (Though I live in Colorado, where the air is thinner and dryer than in most places, and really does make a difference at higher speeds.) In three-plus years I've had only a handful of highway trips under 50 mpg, and all of those involved either cold - low 20s or below - or freezing wind. In the Prius, cold wind and short trips (in minutes) are the real mpg killers.
Mmmmm, interesting.
As 95%+ of my driving is Motorway (on the right hand side of centre :o) I think I'll stick to the BMW Z3...
[E=1/2mvv but mostly goes to 1/2pvvCdA from http://en.wikipedia.org/wiki/Drag_equation]
These guys have got a nice shape: www.aptera.com
Nick.
re: fuel economy vs speed curves
I have a BMW 540 and a 2nd generation Prius and I've driven a VW Beetle TDI across the US. The curves shown are inconsistent with my experience with these cars. The VW got about 48 mpg consistently, as long as I stayed below 75 mph. The BMW will get up to about 26-28 at 65 mph, but doesn't drop below 20, even when driven quite hard on the highway. The Prius needs to be driven at 80 mph or above to get less than 40 mpg, but at 65 it easily stays in the mid to high 40's.
Mark Folsom
Last summer I went to spend a week at my Mom's doing handyman stuff around her house. Denver to Omaha at 75 mph all the way running the A/C, several days puttering around the Omaha suburbs, then back to Denver again at 75 with A/C. 2004 Honda Civic with automatic transmission averaged 41 mpg for the entire trip. All the gas sold in Nebraska has mandated ethanol content, so at least half of that trip was done on E10. I was quite pleasantly surprised at the mileage.
I don't have any driving experience in any of these cars, but the fuel economy at 60-80 mph looks a little pessimistic (a Prius gets 37 mpg at 60mph and 30 mpg at 80 mph?). On my last road trip I averaged 37 mpg in a fully loaded Corolla rental car. I cruised 75-85 mph on the open roads, 60-70 mph in heavier traffic and even sat through an hour of a stop and go traffic jam. I'm pretty sure the winter gasoline was oxygenated with 10% ethanol too.
I took three test drives in the 2nd generation Prius when it first came out. I liked it but it was more expensive than a comparable sized ICE in spite of the government subsidies that were being offered. I was also concerned with the possibility of expensive repairs as it aged. I doubt that the world is going to be saved by hybrids. Still I am enthusiastic about efficient driving and a 55 mph speed limit. I am old enough to recall the 35 mph speed limit of WWII and my father's B card.
Around the time of an earlier gas crisis there was an interesting problem related to the reduction and ultimate elimination of lead in gasoline. The regulations came on fast and and the auto companies found it difficult to adjust. Did tetra ethyl lead save oil? Might be an interesting topic for one of our smart engineers to research. I had a big Ford station wagon at about this time. I did well to get 10mpg.
I can explain that. Tetra ethyl lead is a cheap octane booster and lets engines run higher compression. Higher compression is a win-win all around because it gives better power AND better efficiency. When we moved to unleaded gas in the early 70's because of catalytic converters and environmental effects, unleaded had a much lower octane rating, and automakers reduced compression ratios. In the time since then, we've gotten better at designing combustion chambers that can run high compression on 87-91 octane fuel.
Only 6 years ago, I was driving a 1986 Oldsmobile Cutlass Supreme Broughm that got...
12 miles per gallon.
You could seat 6 comfortably, fit an elephant in the trunk, and almost peal rubber while driving 60mph with the rear wheel drive.
A prius would squash into the grill like a large june bug.
I think the transition to Prius-like cars is going to be a sudden thing in a few years. There are multiple concurrent effects that could make it non-linear.
1)gas prices
2)carbon scare
3)techological proress
4)Nuclear plants plus plug-in options
5)Less fear of the disapearing deadly old steal beasts
6)everyone else has one
We'll wake up one morning and all of the neighbors will be getting 40mpg.
You might be interested in an article that appeared in March in the Times newspaper where a comparison of a Prius vs a BMW 520d driven from London to Geneva using motorways and town driving, a 545 mile journey.
http://driving.timesonline.co.uk/tol/life_and_style/driving/used_car_rev...
According to the test the BMW was marginally ahead despite being a larger car so, your mileage may vary:-)
This website provides both miles per gallon (Imperial) figures, litres/100km and CO2 emissions for new cars sold in the UK.
http://www.vcacarfueldata.org.uk/search/fuelConSearchResults.asp