LEOSOPHIE

Same with my 550.

lkchris

The "data" is that Mercedes are better cars than clearly you can possibly comprehend. They do test these things, you know.

mdadgar

Keep the comedy comin', dude. You're on a roll.

- Mark

pteam

Honestly? thats a pretty dumb comment. There are billions of products in the world that can be improved on. In fact, pretty much all cars are "improved" on every couple years with tweaks, adjustments, and new features, design changes, updates, and new models.

Mercedes might have optimized freeway economy for 55mph but not real world 65 and 70 mph speed limits zones where people go 10 mph and are actually doing 75mph and 80mph.

Also I'm not sure what parts like the 7 speed transmission and rear end gearing are shared with other cars in the Mercedes lineup but they might have just put it in "as-is" instead of changing ratios for the GL or just the GL diesel which could have made it get better gas milage but would have cost alot of money for Mercedes corporate to change stuff just for specific versions. Corporate parts sharing is probably one of the top ways to cut costs.

The 2012 slk's that just came out already have a roof alignment problem. Its bad enough they cant even sell the cars until its fixed. "don't they test these things?"

Every recall on any car ever made could apply to that statement: "don't they test these things?"

My friend was mad because he bought a 2011 chevy cruze and the 2012 chevy cruze is going to get 2mpg more. Gee look at that they made an improvement go get 2mpg more...
"The engineers from General Motors have miraculously managed to improve the Chevrolet Cruze's fuel economy by an additional 2 mpg. The Chevy already has a Cruze Eco option that delivers 28 mpg city, 42 mpg highway when fitted with the six-speed manual transmission.

This 2 mpg increase was attained through lowering the final-drive ratio to 3.53 from 3.87 in the current year's model. This allows the engine to run at a lower speed burning less fuel."

The GL350 could definately improve fuel economy by the same technique of lowering the rear axle ratio.

mdadgar

Yup. All product development is a trade-off among features. In this case, my (educated - I do product development for a living) guess is that Mercedes was balancing fuel efficiency vs. throttle response around town and a reasonable level of gear changing (forestalling the "it's shifting all the time and driving me crazy" customer complaining).

As several people have noted, you can instruct the vehicle to drive in a higher gear around town and get better mileage, but at the cost of reduced responsiveness and more shifting when you want to accelerate quickly.

- Mark

pteam

yea, the problem is you cant upshift one more time on the freeway when its crusing at too high rpms and its already in 7th gear

LEOSOPHIE

With your stable of performance cars why would you even own a diesel, you can obviously afford the fuel.

43221B

For most people (who can drop 70k), it isn't about what they can afford. It is about compromise. Why burn 30% more fuel when cruising down the freeway when you don't need to? Furthermore, other than the Turbo lag from a dead stop, the diesel really does have favorable acceleration characteristics. On the highway for instance, it gives you 400 instantaneous lbft of torque with either no downshifting or one quick downshift when accelerating.

I agree with the comments about the improved MPG potential of the diesel and I would certainly like to see a higher 7th. Having said that, try driving an Escalade/Tahoe/Yukon with all the cylinder deactivation and hunting for gears that goes on. It makes for an awful driving experience. Perhaps Mercedes was trying to avoid those characteristics to a fault.

Brocktoon

As I stated earlier, a diesel engine's consumption is SOLELY dependent upon throttle position, not RPM. Unlike a FI or carb Otto cycle engine, which throttles air, diesels actually only dose fuel. In an Otto cycle engine, this means that fuel is always being added to meet combustion needs of the engine, so increased rpm always means a proportional increase in fuel. This is not the case in a diesel engine, where you are looking for the smallest fuel dose/load. Lugging a diesel under load will use far more fuel than running at higher rpm, as it requires a higher fuel dose. It is possible that in some cases forcing an upshift will result in temporary savings. Our engines are only 2,990cc. it is very possible that a higher OD would result in "lugging" or increased throttle position against the increased aero loads at higher freeway speeds, resulting in higher consumption.

LEOSOPHIE

Wish all you will the torque of a 550 is equal to the diesel over a much greater rpm range and there is no acceleration advantage giving up 150 hp.

43221B

I'm definitely not suggesting that the diesel is quicker in any regard to the 550. What I am saying is that the acceleration characteristics other than from a dead stop are desirable in the diesel. Passing and merging onto the freeway is effortless. By that I mean, no head snapping downshifts and no dramatic or loud rpm change. You would never know there was only a 3.0 liter engine under the hood.

LEOSOPHIE

Understand.

pteam

43221B is exactly right on with my thinking also. Its an SUV, not a sports car. I dont need to burn 30% more fuel going down the freeway. I only use my SUV when its raining, snowing, or when traveling with 3+ people. In all of those circumstances I dont need to floor it and be traveling at unsafe speeds. Nor am I flooring it to get maximum horsepower to pass people in these conditions. Thus I have no reason to get a 550 at all. In fact, in my case, I would have deeply regretted the 550 because it has features that I dont need nor do I want to pay for in an SUV which is 150 extra horsepower and much worse fuel economy. The GL550 is $14,000 more than the GL350 and gets worse gas milage. Now 150 extra horsepower in a sports car is an entirely different story.

Also at no point do I feel the GL350 is underpowered at all. Coming from a hummer h2 its feels nimble and fast, and that thing had a 400 horsepower v8! The turbo boost in this thing is great, however 90% of my driving is just cruising, in which case I enjoy the luxury and good gas milage and not being a glutton wasting fuel where it gets me no enjoyment

Tommorrow Im taking my family on a long trip, Im looking forward to it in this SUV more so than any other Ive had in the past!