Fuel economy of hybrid vs diesel vehicles at highway speeds
 

Hi guys,

A german car magazine has tested lots of vehicles for high speed fuel economy:

http://www.greencarcongress.com/2006...ptio.html#more

Interesting because it compares Prius fuel economy at highway speeds to many other vehicles, including some diesels. For example, the linked chart below compares Prius mileage to Opel (GM) Zafira mileage at various speeds:

Chart of Opel Zafira vs Prius mpgs

For those unfamiliar with a Zafira (see a picture of one here), it's like a kind of minivan, longer, taller, wider and heavier than a Prius, very practical and quite popular over here.

Re: Fuel economy of hybrid vs diesel vehicles at highway speeds
 

Was the Zafira a manual or automatic transmission? The test data doesn't tell.

If it is a manual transmission, they really should use a manual transmission hybrid, say the Civic manual or Insight manual.

BTW, where is the City comparisons? After all, many of us work and don't live at Interstate on/off ramps (Autoban on/off ramps.) So in those wonderful European cities, the hybrids vs desiels did how well?

In engineering, we call this 'cherry picking' the data. Engineers who do this are forced to become Windows system aministrators or write software. We don't let them deal with real things.

Bob Wilson

Re: Fuel economy of hybrid vs diesel vehicles at highway speeds
 

Clett,

I note that this chart claims that the Prius gets 37 MPG at about 60 MPH. That is a ridiculously low figure for the Prius. Mine averages just under 50 MPG at 65 MPH in good weather. Even in rain and or cold I have never gotten less than 42 MPG at 65 MPH in my 2004 (56,000 miles). Don't believe everything that you read.

JeffD

Re: Fuel economy of hybrid vs diesel vehicles at highway speeds
 

Hi Bob, the article was only meant to assess highway mpgs, as may be encountered on a longer trip. I've not been able to translate the German article yet, but I don't think there would be any doubt that Prius would win in city driving.

jdenenberg, the figures they show are lower than expected for all the vehicles - noticeably so for the Prius which I also agree is usually reported by many drivers to do better. I'm not sure why this would be, perhaps it was very wet, or a bad headwind? Without a German speaker to translate the article we may never find out!

Re: Fuel economy of hybrid vs diesel vehicles at highway speeds
 

In an article that specifically tested high-speed fuel economy they aren't likely to have the city rating. This sort of write-up probably makes more sense to someone in Europe than to us in the US. The reason is that things work a bit differently over there. Some use their cars for literally everything, like we do, but this is not the case for most living within the reach of their well-developed mass transit system. Even if you own a car, at $6+ per US gallon it is cheaper and simpler to hop on the Metro and go about your business. This leaves the automobile for longer range weekend and holiday travel to places not easily accessible by mass transit. This, at least, is what I observed while living in Athens. The majority of vehicles on the road were taxis or city busses. So while the review may not be complete, it is useful. I don't quite think that the allegation of "cherry picking" fits. A better example of that would be matching their worst Prius run agains the best diesel runs in order to skew the results, which is obviously a problem.

Regarding transmissions, (again), manual transmissions are largely the norm in Europe. If the Prius were available as a manual they probably would have driven that instead, but it isn't. So they take the best Toyota has to offer and match it against the best Opel et. al. have to offer. That's perfectly reasonable. Especially in Europe.

Re: Fuel economy of hybrid vs diesel vehicles at highway speeds
 

Fair enough. I'll accept that vehicles in Europe are primarily used for long distance, highway driving and seldom negotiate the urban and rural roads.

In this we'll have to agree to disagree. There are two hybrid manual transmission vehicles, the Honda Civic (no longer in production) and the Honda Insight (announced but still in production.) Also, I suspect the test vehicle could have been obtained with an automatic. As long as the transmission types match, I'm prefectly happy but we've had way too many skeptics who think it is perfectly OK to compare a manual to an automatic.

Bob Wilson

Re: Fuel economy of hybrid vs diesel vehicles at highway speeds
 

I followed on of the links to a page that had about 20 versions of this Opel(say-does GM own Opel???).

I would bet that they used one of those automatic manuals. There was at least 10 different TDI-Trans options. One of them was probably an auto manual trans.

I think it these vehicles are a fair comparison-the Opel is 175",64" tall and about 70 wide-it is bigger than a Prius. They compared the best against the best of roughly the same size.
Now I do take issue with the 37mpg at 60 mph. They would have done a short run at each speed for each car. It had to be a brief run, or they could never have done so many cars and runs. 37MPG seems low to me, and I generally tend to down rate most of the MPG figures I see here because they are delivered by fanatics. I wonder how they determined these figures? It had to be by either using the onboard displays, or by hooking into the diag.(like the scanguage does). They certainly didn't do it by actually physically measuring the fuel used. This is probably where the error occurred(if there was an error, and I think there was-at 60 mph anyway).At 60 mph I tend to show in the high 40's+ via scanguage and vehicle display.The Opel has about 15% more frontal area, and certainly has a higher CD.It has a Euro EPA number of 46mpg-the Prius has a higher number-50 something,I think.
I'm going on a long hy trip(3000 miles) with the Prius soon. I'll have a bike strapped on the back that should drop hy mpg by about 5mpg. I'll see what I get.Thanks,Charlie
PS- Bob, I suspect their actual results are wrong. It is OK-by me-to compare best to best, but the 37 mpg just doesn't ring true. Their methods of measuring the actual gallons used were probably kinda casual(they probably also just used the speedometer to "read speed".)

Re: Fuel economy of hybrid vs diesel vehicles at highway speeds
 

Ahh, but what if they tried to? We know that the bladder in the Prius' fuel tank makes for somewhat inconsistent filling since the tank size is essentially variable. What if they started with a full tank, drove for 50-100 miles, filled again to measure consumption, but unintentionally put more fuel in than was actually used during the test? Perhaps the bladder had warmed up and had a bit more give at the end of the run?

Unless they don't have a bladder in the European deliveries, in which case my theory is fairly useless.

Re: Fuel economy of hybrid vs diesel vehicles at highway speeds
 

Nope, no bladder for us. Just thought of another possibility though, could our gasoline be of a different rating to yours in the US? I've read lots of UK magazines grumbling about getting low mileage (like mid-40s). Or perhaps it could be our weather?

Re: Fuel economy of hybrid vs diesel vehicles at highway speeds
 

Nah, they had to use onboard readings to get those numbers.They would have just plugged in their readers and taken what they were given.If the speedometer or the fuel flow was wrong,the results would be wrong.
I don't doubt that a good diesel can match the Prius, but I don't think the EPA-Euro equivalent shows this car getting better hy mpg?
Anyone know where to look that up quickly-
Clett-could/would you look up the Euro Epa numbers for the Prius and this Vauxhall-Opel whatever?
The Prius 60mph 37 mpg are the numbers that don't ring true. My readings at 60 mph are usually high 40's-low 50's. CR got 50 on their hy loop and 48 on their 150 mile trip. 37 seems very low.
Thanks,Charlie