One of the more hotly-anticipated cars of this year is the diesel variant of Mazda's new 6 sedan.

It's a striking car on the outside, but its efficient clean diesel engine should make it striking on the road too--with cleanliness and efficiency being key priorities.

Efficiency is always a priority for race teams too, which is why Mazda fielded diesel race cars in the recent 24 Hours of Daytona. More amazingly, says SAE International, they raced on synthetic diesel.

Synthetic oils have been around for decades, but the synthetic fuel used by the three racers was claimed to develop no smoke. No exhaust after-treatment systems were needed.

Developed by Dynamic Fuels, the fuel is refined from non-foodstream feedstock, based on fats left over from one of the companies behind Dynamic Fuels,Tyson Foods. Several plant-based waste products are also used.

The fuel has a much higher cetane rating than standard diesel--cetane being diesel fuel's equivalent of an octane rating, a measure of combustion quality--and is more resistant to foaming than pump diesel, important during fast refuels under racing conditions.

Sadly, all three racers succummed to a fuel pressure issue by the sixth hour, according to Motor Trend.

Such issues are commonplace for new race cars, particularly with untested technology. It's unfortunate that we weren't able to see the full potential of the 400-horsepower diesel racer, or the benefits of its 25-30 percent better fuel efficiency than its rivals.

Still, all is not lost: The team will be back to compete in more events in the Grand Am series' GT Class--and there's little doubt that it's the greenest race car in the field.


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