German Car Zone

Diesel Vs. Hybrid: We Debate Two Technologies


Sure, you can get sticker shock at the gas station, but you don't have to give up your sport-utility vehicle. You don't even have to give up the carlike luxury trimmings you've come to expect as part of the SUV experience.

That's what the 2009 Mercedes-Benz ML320 Bluetec and 2008 Lexus RX 400h are meant for.

Or maybe you're looking to make a political statement. Those on the right-hand side of the aisle might want to use less imported oil, while left-leaning types just want to use less oil, period. And what better way to represent your social consciousness than with the SUV you drive?

In fact, this comparison is all about the debate. Once you commit to a greener way of life with a sport-utility, which is the better choice, diesel or hybrid? 2009 Mercedes-Benz ML320 Bluetec or 2008 Lexus RX 400h?

Point, Counterpoint

Representing the left is the progressive 2008 Lexus RX 400h — that's "h" as in hybrid. This RX features a beefier version of the Hybrid Synergy Drive system found in that darling of the eco-warrior set, the Toyota Prius. Depending on how hard you leg it, the RX 400h's gasoline-fueled 3.3-liter V6 plus its assemblage of electric motors and batteries can either put 268 horsepower to the pavement or return 25 mpg combined — 6 mpg more than a non-hybrid RX 350.

On the right is the more traditional and conservative 2009 Mercedes-Benz ML320 Bluetec, powered by a 3.0-liter V6 turbodiesel that pumps out 398 pound-feet of torque. The inherent efficiency of the diesel cycle means the ML320 Bluetec is rated at 21 mpg on the EPA's combined cycle, some 24 percent more than the otherwise identical gasoline-powered Mercedes ML350.

Ah, but this is no old-school soot-belching diesel. The Bluetec moniker identifies this ML320 as a diesel that meets the same tailpipe emissions standards required of gasoline engines sold in California — the toughest such diesel regulations in the world.

The Bluetec system combats oxides of nitrogen (NOx), the nasty byproduct of the diesel combustion cycle, by employing two catalytic converters. AdBlue, an aqueous urea solution stored aboard the Benz in a separate tank, is injected into a downstream exhaust catalyst where it reacts with the NOx in a process known as Selective Catalytic Reduction to form harmless nitrogen and water vapor.


Full Test and Video: 2009 Mercedes-Benz ML320 Bluetec vs. 2008 Lexus RX 400h Comparison Test


M

We will se a lot of tests in the near future where diesels will prove to be more efficient in real world testing than gasoline hybrids.

Interesting that the RX matched ML in highway fuel economy.


BTW I think MB should add another warning sign to prevent drivers like tennmb getting too creative with filling the AdBlue tank j/k

Wow the Lexus looks like crap!!

It was great see them rave about the ML interior and how luxurious it felt. I haven't been in a facelifted ML yet, but always thought the ML interior, though well designed, didn't have the greatest materials... The RX on the other hand is pure toyota.

I think there is a huge difference in interior quality between the pre and post FL ML.

These comparisons are always stupid. They knock down the ML for not being a capable off roader because it lacks a spare tire. What they negate to mention is that you would never be caught dead trying to have an off road adventure in an RX 400 hybrid. So how is that even fair game? They also knocked it for being more expensive. Well guess what, they had a fully loaded test car. Edmunds really need to hire some new writers. Their own RX long term test car has been a continuous let down in terms of mileage and other hybrid 'improvements' per performance.