Guest Post >> Mercedes-Benz Diesel by the Numbers: A Case Study

Author: Dave Tobin

I’ve been thinking about gas mileage recently. It seems to be on people’s minds, it’s always been a factor when car shopping I suppose, but my experience this past week shows me that gas mileage really does affect a purchase decision, in some cases, even makes the decision. I’d like to discuss Mercedes-Benz diesel options first. One common objection to the diesel option is “It’s more expensive than gas” after my analysis I don’t think that’s a valid objection at all, you’ve got to look at the numbers.

On Thursday I had a couple come in and trade in their 2007 Chevy Tahoe in on a new GL350 BlueTEC diesel. They live outside the Twin Cities and commute in, easily putting more than 100 miles on their SUV everyday. They need the space of an SUV to haul kids and their stuff, a car isn’t an option for them.

Yesterday a previous Feldmann Imports customer came in with his 2008 Mercedes-Benz S550 4matic sedan that had slightly less than 14,000 miles on it and traded it in on a 2010 S class Hybrid because he feels it’s the responsible thing to do… trade in his big V8 for an electrically assisted V6 Hybrid, he wasn’t using the almost 400 horsepower in the S550 anyway. Hybrids are a great option and we’ll discuss the new Mercedes-Benz Hybrid options in greater detail later this month.

When I look around the showfloor at Feldmann Imports I see an ML450 Hybrid SUV, the gorgeous S400 Hybrid, the first hybrid on the planet to use extremely efficient lithium ion batteries. I also see the ML350 BlueTEC diesel, and then there’s the GL350 BlueTEC diesel. We haven’t received the diesel version of the new E class sedan yet, but it will be arriving soon enough this Spring.

I was at a board meeting for the Twin Cities Section of the Mercedes-Benz Club the other night and got to talking to board member Jim Walrath. He owns a 2008 Mercedes-Benz ML320 CDI diesel. Jim is a Mercedes diesel disciple to say the least, each time I see him he mentions how much he loves the ML diesel. He related that on a recent trip from Northwest Wisconsin where he lives to Boston and back he averaged 30.1 mpg in the ML320 CDI diesel while on the highway, at speed limit speeds.

According to Jim the “overall average was a little bit less at about 27.6. We put on quite a few miles of inefficient city driving so the average was pulled down. Total miles on the trip was 3007.”

Jim went on to tell me more about his ML Diesel, “We have made 35+ mpg on 55 mph highways in northern Iowa. Overall our mileage has been in the 27+ range but we do put a lot of highway miles on it – is is our vehicle of choice on any trip.”

That’s quite a bit more than the window sticker on that car says. I wanted to do a little research because people often look at me skeptically at the dealership when I mention that the bold EPA estimates on all of the window stickers in our showroom are on the conservative side.

I consulted, the website we were told to use last summer during the “Cash For Clunkers” craze when deciding which cars qualified or didn’t qualify for a government rebate for some answers.

I should first mention that starting with model year 2008 the EPA changed the way they test cars for gas mileage, taking in to account the effects of “faster speeds and acceleration, air conditioner use, and colder outside temperatures.” Basically, estimates went down.

According to the website, the sticker on Jim’s ML diesel in 2007 would have said the ML320 CDI 4matic would get 21mpg city / 27 mpg highway. The sticker, for the same vehicle based on today’s ratings would say 19 mpg city / 24 mpg highway. And after talking to Jim I know that he gets slightly over 30 mpg highway and over 20 mpg in the city. No doubt, that’s good gas mileage for an SUV that’s got a gross vehicle weight over 6000 pounds and has a towing capacity of 7200 pounds.

According to it only looks like diesel is about 20 cents more than premium unleaded, which you’ve got to put in every other Mercedes-Benz vehicle anyway. The gas tank in the ML is a touch over 25 gallons at 20 cents a gallon, so it’s about $5.00 more to fill up the ML 320CDI than a normal gasoline ML350 4matic that has the same fuel capacity.

It comes down to cruising range… according to published vehicle specs the cruising range of the ML diesel on 25.1 gallons of fuel is 577 miles. The same 25.1 gallon capacity in the ML 350 gasoline V6 only has a range of 477 miles. So, the $5.00 extra it took to full up the diesel looks to be money well spent as far as I’m concerned.

In my experience there seem to be two types of customers when it comes to Mercedes-Benz diesels. One is the customer who walks in and says “Where are the diesels? I want to go for a test drive” the second is the customer who responds, “Don’t even bother telling me about them, I don’t want a diesel, I’d never buy one.”

Mercedes-Benz has been making diesel powered vehicles since the 1930s, of course they’ve come a long way, the newest generation of clean diesel BlueTEC engines are the cleanest, most efficient diesel engines ever produced. They’re a far cry from the old 300SD from the mid eighties that would shroud its departure in a screen of black diesel smoke. The new diesels are winning awards around the world for their eco friendly design and they’re certainly worth having a look at.

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