For a start, 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. It 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 be cost-effective at current fuel prices yet, but things may look very different by 2020 or 2050.

Anyway, both of you have valid points. When I feel better–maybe tomorrow I will address both of your points in a post.

In general, while more civil than I usually hear–thank you, these are the general arguments that I hear. Between the two of you…..you have come up with a better technology. *regenerative braking, regular gas, 500 pound lighter, hybrid* wahoo.

Thanks for your comment. I appreciate people who are interested in hearing other points of views, especially views so different from their own.

That being said, I have some questions/points about the efficiency of the BMW. First, was it a manual/standard transmission? Manuals are more fuel efficient in general than automatics (which I assume the Prius was). Secondly, the BMW runs on diesel, so even if it is a fraction more fuel efficient, the fuel it is burning is less clean than that of the Prius.

I’m not personally a huge fan of Priuses (Priusi?) and I don’t think hybrid technology is the answer to our transportation problems. In fact, I don’t think there is any one solution; we’ve got to get creative and approach the problem from multiple angles.

I consider myself both an environmentalist and a pragmatic, rational, reasonable person. So I hope to be your first reasonable argument from an environmentalist. *grin*

P.S. If you want scientists who base their careers on fake premises and bad science, look at the climate change deniers.

For all I know, maybe a hybrid that’s 500 pounds lighter and has a regenerative braking system may be the way to go. I say, thank you BMW, thank you Toyota, thank you engineers who continue to tinker, test and run these sorts of trials.