107123210

Buckeyesoldier posted this in another thread:
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. Car has done about 7800 miles.

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.

Cwdawson

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

Rdub

Actually, it is not hard @ all !

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

fabbrisd1

If you want to max fuel economy - highway - then peg cruise control at 57 mph.

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.

Bob338

Somewhere here I posted to a thread about this. Don't remember the exact mpg I got but when I had to drive under 50mph using the inflatable spare for about 400 miles, I got well over 40 mpg, maybe as much as 48 mpg. On trips I usually drive near 90mph and consistently get 36 mpg at those speeds. For stop and go, and short 'less than 30 mile trlps' in my rural area I'm averaging 32 mpg.

ferreirabill

"So how do others get 40+ mpg with same vehicle?"


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.

koalatm

Our lifetime average in our GLK (30,000 km / 20,000 miles) is 7 litres per 100 km, which equals 33.6 US MPG.

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.

cjmoy

I've been averaging 31 in mixed driving / traffic. On long trips I've gotten 35.

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.

LesF

it all depends how you drive.
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.

rmfnla

Not in LA...

107123210

My figures are in US mpg (same as GLK display). In Imp mpg, my figures are 32-42 mpg. But the figures most post here are in US mpg, and that is what I was questioning.

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.

fabbrisd1

#1 - there are no "mileage claims" - there are tested governmental standards under identical conditions - so that consumers can judge between different vehciles.

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...;

buckeyesoldier

So I'm quoted in the top of the thread and just wanted to provide more info about my trip:

-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!

cjmoy

No kidding, LA traffic is

I was averaging 20 mpg in my previous Tiguan, so even 31 is fantastic.

rmfnla

Yeah, my GLK is a gasser and I get maybe 21 or 22 if I'm being good...

107123210

I think I would post it too IF I ever got 42mpg

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.

twinturba

It all comes down to driving style. A friend of mine has the same glk250 as I do, had a wife a kid in the car same as I did, only difference is I have a cargo box on top. We both completed a round trip from the Bay Area to Lake Tahoe last weekend together, staying in the same place, and driving the same route, but I averaged over 2 mpg better.

Fyi, this month I have 2 round trips to Tahoe and have completed over 512 miles per tank both times.

Rdub

So what mpg do you actually POST on your Tahoe round trip/s (512 miles) and each leg, and traffic flow details (with and without cargo box) ?

twinturba

Here is the data as calculated on Fuelly for both tanks of gas from my two trips so far this year, both with the cargo box on top, just above 33MPG average.
# 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.

Rdub

Thanks for both the response and data (same app destination, altitudes, one with outside cargo box and 2 others sans the cargo box ). So between Bob338's msg #5, my posts and yours, one can see a broader RANGE of potential mpg postings. The cargo box obviously has a pretty good toll on mpg ( minus- 6 mpg or up to MINUS -15.3%).

twinturba

No Problem, I love tracking the mileage on trips.
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

Rdub

Well,it is VERY accurate for that PORTION of that leg. Now if you are counting your WHOLE leg, no. If you are counting round trip, no. HOWEVER IF you didn't GET 44.5 mpg on your picture 128 mile leg, NONE of (that) your data would be valid/changed.

eki912

Speed does make a big difference :

http://www.mpgforspeed.com

And GLKs surely are not aerodynamically the best design, thus speed & wind will affect it even more than sleeker sedans.

twinturba

No matter the trip computer accuracy, my actual mpg is higher than any car I have ever owned. The ML bluetec which was replaced by my GLK had about 100 more miles total range on average, but only averaged mid to low 20's MPG.

LesF

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.