Toyota Prius hybrid versus BMW diesel

The Sunday Times did a road test, driving a BMW 520d SE and a Toyota Prius from London to Geneva. The BMW used 49.3 litres of diesel, versus 51.6 litres of petrol (gasoline) used by the Prius.

While the BMW’s results are clearly respectable, the figures quoted in the Sunday Times article do not tell the whole story.

For a start, about 40% of the trip were on motorways, another 40% on B-roads and the rest in urban areas. A driving mix that includes only a token 20% of urban driving is hardly typical for usage patterns of most motorists in our largely urban / suburban societies (for example, 79% of the US population lives in urban areas, with most European countries having similar rates). This unusual mix seems almost purposely designed to ensure that the advantage of the hybrid drive train of the Prius would lie mostly idle: Driving at constant speed on a flat road, you are not going to see any real benefits from a hybrid system, which really thrives in stop-and-go rush hour traffic with lots of traffic lights, as most of us experience on the way to work or home.

Secondly, even with these skewed parameters, the BMW lost out on greenhouse gas emissions. It burnt 10.84 Imperial gallons (13 US gallons) of diesel, while the Prius used 11.34 Imperial gallons (13.6 US gallons) of gasoline. Because of diesel fuel’s 15% higher carbon content by volume, the BMW added 131 kg of CO2 to the atmosphere versus 120 kg by the Prius.

Personally, I see no reason why in the long-term efficient diesel engines can not be mated to a hybrid system and have the best of both worlds. Sure, it may not yet be cost-effective at current fuel prices, but things may look very different 10, 20 or 30 years down the road.

3 thoughts on “Toyota Prius hybrid versus BMW diesel

  1. I agree that the comparison was not fair. However, I believe the fairness was biased toward the Prius. The 520d is heavier, larger (less slippery) and ran the air conditioner during the trip. The driver of the Prius admitted to trying to get the best efficiency possible and still did not equal that of a larger heavier luxury car. I am appalled that people are still influenced by style, celebrities and media, but do not look deeper into the claims. I do believe that the Prius would have fared better in its element. However, if it were compared to a 320d instead of a 520d I feel we would see a similar outcome. My 2003 Toyota ECHO has a similar engine as the Prius and gets 40MPG (US) consistently without the added cost (both financial and ecological) of batteries and electric motor. In my opinion, hybrids are the car manufacturer’s way of telling us yet again that they cannot meet government economy mandates. Remember the GM EV1 fiasco in California?

  2. The 520d is indeed larger and heavier than the Prius, but its interior space is comparable to the Prius (according to the EPA in the US, which lists the Prius in the “mid-size” category along with the Audi A6 and BMW 5-series). The Prius offers considerably more rear leg room than either a BMW 3-series or Audi A4.

    Therefore I would argue that a BMW 3-series would be a closer match for the new Honda Insight, which is considerably smaller than a Prius.

    As for your Toyota Echo (which is either a Toyota Platz or Vitz/Yaris, depending on the market), it’s a great car, reliable and economical. I drove one of the second generation Yaris as a rental car during my last holidays and one of my friends in Germany has one and is very happy with it.

    It is not directly comparable to the Prius, as it’s smaller than a Corolla, which in turn is smaller than the Prius. In fact the Prius is closest in interior size to the Camry (also rated “mid-size” by the EPA).

    Despite its smaller size, the Echo/Yaris does not quite match the Prius on fuel economy. The 2009 1.5L automatic model is rated by the US EPA at 29 mpg (city) / 35 mpg (highway) / 31 mpg (combined). The NH20 Prius (old model that I have, the new model coming out next month is better) is rated at 48 mpg (city) / 45 mpg (highway) / 46 mpg (combined). The 2003 Echo is rated at 28 mpg (city) / 36 mpg (highway) / 31 mpg (combined).

    Let me say that there is no one car that is best for everyone. We all have different priorities.

    If spending little money on your car was your top priority, the Yaris probably is a good choice. At 2$ per gallon in North America the higher purchase price of the bigger, but more efficient Prius will probably outweigh that little extra fuel used by the non-hybrid Echo/Yaris.

    What I like about the Prius is the combination of low CO2 emissions / excellent fuel economy without having to make sacrifices on space and refinement that other economic cars imply.

    Most of my trips by car are short ones to one of two local train stations about 3 km away (2 miles), picking up or dropping off a family member. The whole round trip will take 15 minutes while passing *seven* traffic lights. Fuel economy in most cars under those conditions would be atrocious. In Prius I still averaged 17 km/l = 40 mpg (US) over the past 9 months. I would usually fill up after 600 km instead of a little over 300 km in the Audi A4, despite the Audi having a fuel tank almost 50% bigger *and* my passengers have more leg room than in the Audi, which also was significantly more expensive to buy and maintain.

    I’m not sure how a modern diesel would fare on such short trips with many traffic lights, but I didn’t really have much of an option because until very recently, there were virtually no modern diesel cars on the market in Japan.

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