I ran a car on biodiesel and got 42-44 mpg (this was the first time I worked out real mpg, as I brim to brim filled it cos there was just this one biodiesel place)- when I switched back to pump diesel, I went up to 52-54 mpg, so yeah I would say biodiesel has less energy! Nice peanut smell from the tailpipe though.

Diesel drivers were self-righteous, when "clean diesels" advertising said they were clean, so they could sell diesels at the beginning of this decade. Diesel drivers still don't care about emissions.... & are still self-righteous.

I disagree entirely, nobody buys a car based on its emissions, most people are only interested in the economy, which does relate to emissions in some respects. The emissions of passenger vehicles are published on the registration documents, but apart from C02, people show little interest in emissions.

Diesels put out less CO2 but more NOX - that's the latest issue.

:eek: Really? How do you account for all the "green" people buying hybrids?

He's got me on self righteous...!

Hybrids have been around for decades, and people buy them because they're after economy, I very much doubt people with hybrids buy them because of low emissions, in fact I think most people would struggle to answer if you asked them how much C02 thier cars emitted!

I have recently had my eyes opened to the mk1 insight, and my reasons for buying it would be:
1 better Mpg than my current car
2 I absolutely love the styling, light green colour, silver wheel trims, groovy interior
3 it will stand out, a head Turner due to rarity
4 free Road tax
5 I d get to feel self righteous - more so even than with my diesel!
6 the eco friendly angle

OK, lets take it one step farther- electric cars. Zero emissions and they are marketed that way by the manufacturers. I can guarantee you that the people who are buying those aren't buying them for the economy. Take a look at Tesla and the people who buy them. I don't think someone dropping $79,000+ for a S model are worried about economy. Have a look at their website: Model S | Tesla Motors What's the first feature that they are selling? Zero emissions.

You and other members from the UK keep going on and on about your emissions road taxes and how it was one of their factors in buying the model of the car they own. Don't give me that BS that people don't buy cars based on emissions.

Let's agree to disagree.

Crossed threads slightly, I was actually talking about the US, where auto emissions are not as openly published and are hard to come by than they are here. As you say, there are very few emission based incentives to buy low emission cars in the US (Road tax, congestion zones etc) so it's more common that car owners chase mpg numbers rather than emission figures.