Mileage Claims
During summer, our mileage was at best 35mpg.
So how do others get 40+ mpg with same vehicle? I can't see any way of achieving that regardless of how we drive. Our V-6 E320 gasser did just as well.
Last edited by 107123210; Jan 19, 2015 at 09:10 PM.
Well, I just completed a trip from Ontario, Canada to SC - about 1000 miles. We drove at the most 10% over posted speed limit on I-81 (55-70). GLK250 was full, but not heavy stuff and there was just the two of us. We has Thule box on top, but fuel consumption was about same as for same trip last year without box. 27-28 mpg on car computer and by calculation.
During summer, our mileage was at best 35mpg.
So how do others get 40+ mpg with same vehicle? I can't see any way of achieving that regardless of how we drive. Our V-6 E320 gasser did just as well.
Are you talking US or Imp MPG, I use imperial and we have a few over 40 mpg with most being in the 30's and thats not even trying hard. Seasonal does seem to effect it somewhat but overall very pleased with the mileage... you can check it out on fuelly we have kept track since day 1...
http://www.fuelly.com/car/mercedes-b...wdawson/269578
In fact, I would hazard a guess that YOU drive YOUR GLK 250 B/T in such a way AND IN environments as to post the mpg* (27 to 35) YOU do ! ?
So for example for 90 miles (South Lake Tahoe (7,382 ft highest altitude) heading down to (past) Sacramento, CA ( a bit above sea level) 49.9 mpg (yesterday). I didn't exceed 90 mph (80-85 mph most) for the rest of the way and posted an over all 42 mpg.
* footnote: 128 oz= 1 US gal
Last edited by Rdub; Jan 20, 2015 at 11:17 AM.
Then over that speed - aerodynamically - your fuel economy drops geometrically.
Variance at pre-set speed then depends on wind direction/force at that time - ie, headwind knocks you down, tailwind helps maximize - same as a aircraft.


At approximately 50MPH, +/- depending on the vehicle's total aerodynamic footprint, about 1/2 the energy consumed is to push air out of the way. The energy to push air increases as the square of the increase in speed.
Example: if such a vehicle is using one gallon per hundred miles to push air at 50MPH then it is using 4 Gallons to push air at 100MPH (100/50 squared). This raises the total consumption per 100 miles from 2 gallons to 5.
Furthermore, diesel efficiency drops faster with RPM than does consumption for gas engines. Based on some very unscientific tests on my part, the optimum RPM for the GLK250BT engine is 1500-1600, over that, fuel consumption increases out of proportion to speed increases.
Altitude and outside temperature also have significant impacts. Driving on a cool humid day, at sea level, with an outside temperature that requires neither heat nor A/C will yield 10-20% better economy than driving a 5,000' at 100 degrees outside with the A/C running.
So move to Seattle for the best economy and stop speeding.
On the highway it does better, around 6.7l at 130 km/h.
I'm sure if I attempted to maximize economy, it would be easy to get to 40 MPG, even in the city. I'm an aggressive driver, and my driving style always eats fuel faster compared to most.
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Today I experimented with driving a lot less aggressively on my 28 mile commute to work and got 40 mpg. I was surprised to hit the 40 mpg mark, but I don't think I could drive in the way needed to consistently achieve that number.
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this was a road trip from Palm Beach to Memphis via Atlanta and back.
It includes about 90 minutes of stop and go through Atlanta. Highway speeds were 70-75mph (1900-2000 rpm) and it included some mountain driving in North Georgia.
The best mileage I've had is 42.4 on a 120 mile trip averaging about 56 mph. The sweet spot for my high mpg is 1400-1700 rpm.
Make sure your tires are properly inflated for load and temperature to maximize your MPG.
Last edited by LesF; Jan 22, 2015 at 12:05 PM.
Today I experimented with driving a lot less aggressively on my 28 mile commute to work and got 40 mpg. I was surprised to hit the 40 mpg mark, but I don't think I could drive in the way needed to consistently achieve that number.
Not in LA...
http://www.fuelly.com/car/mercedes-b...wdawson/269578
Some question the way we drive. On a trip like the one described in post #1, it is hard to imagine many driving more conservatively. We have GLK on cruise control and maintain speed of other traffic, which is usually about 10% over the posted speed limit. The section from Canadian border South to Virginia is quite hilly. We did see an improvement in mileage once through that, but still we couldn't get better than about 29 mpg.
On trips from our home in Kingston to Toronto Ontario, we achieved 35 mpg at about 120km/hr or 74mph. But that is in summer with no roof box or bikes on hitch mount. Also less load by about 200 lbs.
I still just can't see how those higher figures could be achieved on my car. There must be a difference in settings or in the energy content of the fuel.
With the higher cost of diesel vs reg gas, a Subaru Outback or similar gasser might have better economy.
No one has "questioned your "driving" - you have asked - and been answered by several here - you substantially increase your fuel economy by setting you cruise to a lower speed.
Then you can assess the comparison between w/roof-box and no/roof-box.
It's really that simple - your choice of balance between speed and fuel economy...;
-It's was about 485 mile trip we took to and from reno
-I had the trip reset meter set when we left and on the way back I had the "since start" meter as well.
-The whole way I was going about 70mph, sometimes 75--mostly on cruise
-When we got home I still had a quarter of a tank left (I pumped gas before I left)
-The since start meter, which only represents the leg coming home, read 42mpg
-The full trip meter read 39mpg but I don't remember what it was from my house to reno
On my daily commute I drive about 25 miles of mostly back roads so lots of stop and go. I average about 29-32mpg so I'm not saying this is Gods gift to humanity. Just saying that for me to get home, already happy, after enjoying the car's handling on the trip home plus getting home and seeing the meter read 42mpg definitely felt great. But yeah, I don't always get high mpg, but when I do, I like to post it on forums! Haha!

What I find odd, is that down here in SC, with a mix of highway/city driving I am getting about same mpg as we got driving South on I-81 at 60-75mph with cruise control on most of time.
What I also find odd in SC is that diesel costs 43% more than reg! Must be hard to justify a diesel based on better economy. In Canada, fuel in general is more expensive, but diesel only 20% more than reg at present.
Last edited by 107123210; Jan 24, 2015 at 11:34 PM.
Fyi, this month I have 2 round trips to Tahoe and have completed over 512 miles per tank both times.
Fyi, this month I have 2 round trips to Tahoe and have completed over 512 miles per tank both times.
# Date Miles Gallons MPG Price Note
21 1/16/15 518.70 15.49 33.48 3.099
20 1/4/15 512.70 15.48 33.12 3.190
One of the trips had stop and go traffic all the way up to Tahoe, but both trips were fairly free flowing traffic on the way back. They both include all street driving in and around Tahoe for three days each and an average of two "pitstops" for food and restroom breaks each way. The trip computer Usually reports a little higher than the actual calculated numbers on Fuelly.
Last edited by twinturba; Jan 25, 2015 at 01:02 PM.
# Date Miles Gallons MPG Price Note
21 1/16/15 518.70 15.49 33.48 3.099
20 1/4/15 512.70 15.48 33.12 3.190
One of the trips had stop and go traffic all the way up to Tahoe, but both trips were fairly free flowing traffic on the way back. They both include all street driving in and around Tahoe for three days each and an average of two "pitstops" for food and restroom breaks each way. The trip computer Usually reports a little higher than the actual calculated numbers on Fuelly.
Last edited by Rdub; Jan 25, 2015 at 05:25 PM.
I regularly get over 40mpg from Tahoe to Vacaville (one of our pitstops), but think that coasting down the mountain isn't an accurate tell.
Time and MPH data missing to avoid the man

Last edited by Rdub; Jan 28, 2015 at 10:51 AM.
http://www.mpgforspeed.com
And GLKs surely are not aerodynamically the best design, thus speed & wind will affect it even more than sleeker sedans.
Last edited by eki912; Jan 29, 2015 at 07:30 AM.
Agreed.
I've had Es, and the best highway miles I ever got was 33 with a '98/320, with real 100% gas.
With the up to 10% ethanol they sell now(giveaway to the ethanol industry) the best I ever got was 29-30 with an 05/320.
I do much better than the EPA sticker on average, about 10-15% in a heavier and much less aero car.
Last edited by LesF; Jan 29, 2015 at 08:12 PM.



