pteam

I took two road trips in the last 2 days. Yesterday in my 2011 GL 350 Diesel and today in my Porsche Boxster S. All freeway driving tracked.

The results:

Porsche Boxster S: freeway driving 24.5 mpg
Mercedes GL 350: freeway driving 28mpg

Not to mention the GL has like 2,300+ lbs more weight and can seat 7! Also in my viper and lambo I average 10-14mpg so the GL pretty much doubles it in fuel economy.

I have previously gotten 30mpg on a roadtrip with my GL. Love this diesel!

lkchris

The Merc engine is likely smaller displacement.

In any event it sure has higher compression, which is a significant key to obtaining efficiency. Perhaps if your Porsche had similar compression it would deliver better efficiency.

Finally, diesel fuel contains more energy per unit than any form of gasoline, so it should naturally require less of it to do the same amount of work.

vntgspd

Interesting observation, but when I drive my Porsche, fuel consumption isn't really something I track. I find that the number of apexes clipped, perfect heel/toe downshifts, and four wheel drifts are data points worth tracking!

lkchris

Yes, a bit of apples/oranges for sure!

Brocktoon

Whatever, guys. I'm still impressed. Don't forget the Benz is pumping out 40% more torque than that Boxter at the same time. The efficiency of these things is amazing, yet few North Americans will enjoy them as long as diesel is more expensive than gas in the US. Instead they will be sold the dream of electric and hybrid cars that are all about environmental and economic image, not fact.

ddcha

OP reminds me of the old cartoon "richie rich". Anyone remember that?

NorseWagon

Well, in my neighborhood diesel is about the same as premium gas, which my E-500 has a liking for. After almost 2 years and 14,000 miles I have averaged 15.8 MPG on mixed driving.

Now looking at getting a 2011 ML-350 Blue-TEC turbo diesel.
Assume that is the same engine as you have in the GL Mr. pteam..?

The ML comes in at slightly less than 5K lbs. Is the GL considerable heavier or in the ballpark?

At any rate, I should be able to cut my fuel cost with 1/3 and that should pick up 10% of the monthly lease payment..That is the theory anyway..

Any issues with the diesel so far? Noise, smoke, turbo-lag...?

giffie

Nope, nope and nope!

Brocktoon

I think he owns a high-end limo and transfer company, IIRC. Can't do that without the hardware.

pteam

Brocktoon is correct with the above statement. I also own several different internet ventures. That being said, I'm all for efficiency. Why would I buy the gas version of the GL when the Diesel was $1000 less MSRP, Diesel tax credit, and significant gas savings.

I got to where I am at only 30 years of age all by myself by making good money and spending less than I make. I calculated it out and I'm saving about $2,000 per year on the GL over my previous Hummer H2.

However my main point on this thread had nothing to do with me and how much money I make or don't make, but how amazing a 7 seat SUV with significant weight can outperform by getting better gas milage than cars that weigh thousands of pounds less and have much better aerodynamics! Also if Mercedes made 7th gear higher in these cars and we were crusing at lower RPMs at 70mph it would get even better gas milage.

mdadgar

Amen.

It is truly amazing to me how few people have that second part figured out.

- Mark

NorseWagon

I was not aware of any diesel tax credit.
How much?

Just got back from the dealer this PM: Drove an ML-350 Diesel.
Not impressed or disappointed, more like neutral..

Guess I will wait for the 2012 unless they coue out with some smoking hot
$399.00 lease on the 2011s.

pteam

The tax credit may have expired on 12/31/10 - http://www.fueleconomy.gov/Feg/taxleanburn.shtml , but it was $1800

dbtk

I believe the GL350 does come with a 7-speed. At least my 2010 does. Maybe an 8-speed would be more like it...ha, ha, just kidding. At 60mph the engine would be turning at about 1200 rpms.

NorseWagon

Aye, too late..

Perhaps it will come back.
Makes more sense to push diesel cars than mixing ethanol in gasoline...

mdadgar

Unless the US Government is paying you a lot of money to grow corn for no reason.

- Mark

NorseWagon

Yeah, it has that angle to it so everybody can cash in on the warm and fuzzy feeling: Not only are we making "green" fuel right here in the US to lessen the dependency on the Arabs, but we are also keeping the farmers
occupied and that will boost the economy of course..

pteam

Yes it does have a 7 speed. But 7th gear needs to be geared higher. At 70mph its over 2,000 rpms. If 7th gear was geared higher and at 70mph the engine was only at 1500 rpms it would get much better gas milage. Not to mention people cruise at 75 or 80mph all the time, especially now that some freeways around here have 70mph speed limits. At 80mph you'd probably be at 2500 rpms which is way too high for fuel economy.

YYZ-E55

The third turbo lag "nope" is a bit of a stretch. The turbo lag from a stop is painful.

dbtk

Agree, however, manufacturers try to optimize test results for EPA highway fuel economy based on 55-65mph. My Cayenne TT has an 8-speed (as do others including Audis, BMW, Lexuses, etc.) and it turns a little over 1,100 at 60mph.

lkchris

Not a bit of it.

The car is geared for its best efficiency as it is.

Please recall that this engine is less than 180 cubic inches.

The biggest problem at 70 mph is aero drag.

mdadgar

Do you have data on that?

- Mark

Brocktoon

He's right. Ever heard a semi on the highway? They are not exactly loafing at 800 rpm. Let's not forget that diesel consumption is based solely on fuel injected. This is unlike gas engines where more rpm = more air therefore more fuel. Diesel requires an new way of thinking about rpm. rpm does not necessarily = consumption.

mdadgar

I hear what you're saying, but that's a pretty big oversimplification. RPM and consumption are still very closely related. Keep your transmission artificially low when you drive and see how it affects your mileage.

I still want some citations of actual data from lkchris.

- Mark

pteam

I upshift all the time in the city past what the computer wants to have me at (higher rpms) and I can see my gas milage on the data climb higher right away after the RPMs drop.