ddeliber

I bought a 2010 e350 RWD (25k mi) a few weeks ago (absolutely love it) and I am seeing some pretty low MPG numbers. I was hoping that a couple people here could help me out by letting me know if my numbers are in line and if not what I should expect to see (what is everyone else getting).

I started out for the first week or so simply enjoying the car, not driving particularly fast or aggressively, but still driving it. Then I started playing with the trip computer an I noticed that it was showing around 15 MPG for about the past 20-30 miles. Well the specs call for 18/26 so I am now wondering if something is wrong.

I understand that the running averages aren't that good of an estimate, at least not for relatively short trips so I am not totally panicking or anything. However, I thought that it was worth exploring some. 18/26 isn't that great, but 15? The thing can't be off that much right? Since reset (probably just under 200 miles - reset when I picked up the car) was showing just under 17 mpg. I traded in an 04 Infiniti I35 (not a particularly economical car itself) to get my E and it consistently read 24ish mgp.

So I began driving in grandpa mode (no offense to any grandfathers out there, just trying to keep things light here) literally trying to keep it under 2k RPM and doing a lot of coasting, not much accelerating. It has improved, but now it's at around 500 miles since reset and still showing around 17.8 mpg. The trip for each day (~40 miles when I go into the office) can get up to between 20 and 21 mpg, mixed around 60% city 40% Hwy, less when I am driving around town. I am still in grandpa mode so whats up?

Is this what others are seeing? Doesn't it sound low? Could there be something wrong? It would be helpful if a few people would take a look at their trip computers and post their numbers (trip, since reset, driving style).

I'll break out the pad and paper to get a more accurate estimate (actual miles/gallons), but I gotta find something out soon. I am going to go crazy if I keep on driving like this!

ImInPA

Calculate your mileage at the pump based on actual fuel used. The specs are only estimates. A lot depends on traffic, city Vs. highway, the slope and grade of the roads, and most of all, your right foot. Just enjoy it. Benzes are not known for fuel economy, but, if that was a concern, you did yourself an injustice by not checking out the Bluetec diesel.

BM2BZ

don't sweat it. mine is around 10 mpg . just enjoy driving it .

BenzV12

I drive it around 1500 RPM and posted images demonstrate how good fuel eco you can get with these cars .
My car has a 80 liters capacity and fully filled it up shows 1052 km by driving carefully you can even get a few more out of it lol

Trip com shows around 5 liters per 100 kms driving like 80 km/h and RPM around 1500 , holy moly this is a MB and weights more than 1.6 tons
This image also shows distance 903 kms but I drove it around 80 km/h and kept the rpm 1500-1750 by the time I got home these distance dramatically increased.

I remember combined driving in these conditions register as low as may be I should say as good as (lol) 7.5 lt per 100 km , I don't have an image for it.
Driving not enjoying yourself has its own rewards of course and return you in better mpg lol

Fuel economy is not my concern but I like to have extended fuel visits.
I also coast down when getting close the turns , rarely kick down or floor it , I let my foot off the gas pedal around 3500 RPMs when getting accelerated otherwise I can easily see red area lol

I may sound like to have adapted conservative driving style that's mostly like this but I occasionally like to enjoy it too . Special treat

ddeliber

Thanks for the replies. My main intent here is to find out if there is something wrong along with a little curiosity as to what others are getting. I knew that she was a pretty thirsty machine when I bought her. Even if the mpg.#s are what I am seeing I will still enjoy the car. I just thought I would check to see if things are not right - is something broken. gramps mode gettn 21 isn't what I expected, still love it tho.

HBerman

Look at the consumption meter on the MFD when you are going up some of the hills in Boston. You'll see readings below 10! There cars are good in steady state. Take a drive on the Mass Pike for about 50 miles and see what the mpg readout is then. My guess is that it will show 25 mpg. Your 21mpg sounds about right for non-aggressive driving. Enjoy your car.

ddeliber

I hear you HB, I've been watching the meter and I see what conditions use more gas. I haven't done a mostly highway trip without traffic yet, I guess I'll see this when I get there.

Just did the math from the two fill ups since I bought the car. 16.8 MPG for 607 miles mixed cty 60% and Hwy 40% a little less than half of that was being hyper conservative, and the first half wasn't totally aggressive either. Seems pretty low for a car that is supposed to get 18/26. Anyone else getting similar numbers? Is this worth a question to the dealer -> is there something wrong - which is my real concern?

Oh yea, I'm driving normal again :-)

HBerman

Do you have the transmission in "S" or "E" mode? "S" mode delays the shifts to a higher rpm (1st gear starts as well) and yields lower economy than "E". Remember, these cars weigh 2 tons and that is a lot of weight. Get the transmission checked out, but if there are no codes, then just enjoy the ride.

ddeliber

Its in E (on my car it is a C). I put it to S twice but only for a short time to see the difference.

no_mulligan

ddeliber,
Looks like you drive in the northeast. If so, you are on winter blend gas which typically contains more butane and result in poorer fuel economy when compared to summer blend. These are federal and state mandates. It has to do with tweaking the gasoline volatility as air pressure rise or fall seasonally to resist evaporation. Also, as air temperature drops, for every 10 degrees, tire pressure drops 1/2 to 1 psi which can drop you mpg 0.3% (per U.S. Dept of Energy).

Arrie

First of all, you cannot trust the trip computer. I had a 2011 E350 and its computer showed 1 -2 MPG higher values than actual. You have to calculate at the pump from the actual miles driven / actual fuel used.

This said you might indeed have a problem if when your computer shows 15 and then the actual would be 2 MPG less? Calculate at the pump. Maybe your computer shows lower than actual MPG?

I personally dont care about city MPG as it can be everywhere. I drive almost all highway and can tell you something about that.

My car gave me up to 25 MPG with speed of 77 MPH but sometimes it was only 23 MPG. The difference is in driving conditions but also the fuel has a lot to do with it. Came to find out that very few gas stations sell 93 oct. It is adverticed on the pump but clearly is not. Fuel octane rating has a lot to do with it.

Go do a test on highway where you can keep constant speed, i.e. 4-lane highway at no rush hour. Stop at a gas station and fill up. Go drive constant speed for 100 miles or so and fill up again. Calculate MPG.

With 60 MPH you should get around 28-30 MPG. With 75 MPH it should be 24-26 MPG.

Or that is what my car did. You should get well over 20 MPG during any highway driving.

ddeliber

I did the calculation from the 2 fill up receipts since reset when I picked up the car. 16.8 mpg mixed for 607 miles.

Arrie

16.8 for mixed is not that bad but there is too many variables to know how it really is. Do it on highway only as I explained in the previous post.

Nuru

These numbers sound very good for a 2010, seems very close to what I am hearing for the 2012 when one has an aggressive foot. When you did this test, was this done with 91 or 93 octane gas?

ddeliber

While I agree that there are a lot of variables, I just thought that for mixed cty/hwy it would be closer to the 21 that they say claim you should expect. Especially when driving as conservatively as I had been for the last 300 or so miles. This is why I thought that there might be something wrong.

I don't have any reasonably long trips planned, but I will definitely fill up before and after my next one.

Any other opinions out there?

ddeliber

One other thing, most people (at least around here) have 4Matics, my car is RWD and that is where I get the 18/26 vs 16/24.

HBerman

It is cold in Boston now. The ECU will supply more fuel and the transmission will shift later in order to warm up the catalytic converter and to increase the idle.

Here's an interesting article on EPA testing:

http://www.caranddriver.com/features...-mpg-estimates

Arrie

You need to get that 27 mpg with constant 60 mph speed on highway to be able to get 21 mixed. If you drive all city you will never get 20 mpg. It will be only 16 - 17 mpg.

Any you don't need to plan a trip. Just get on an interstate hwy where you can drive about 50 miles straigh. Stop at the first exit and fill-up all the way. This means let the fuel gun kick off 3-4 times. Make sure you fill highest octane. Reset your trip computer.

Then drive about 50 miles and turn back and drive to the same gas station and fill-up again the same way. Then calculate the real fuel mileage.

If you set your cruise to 70 for the whole trip (other than when you make the turn etc) yoiu should see mpg at around 26. If you drive 60 mph it shoulod be around 29 mpg.

As you say you drive like a grand ma and you are getting well below 20 mpg and half of your drivibg is on hwy you are probably getting 3 -4 mpg less in the highway driving test and if so you probably have a problem somewhere, which could be as simple as dirty fuel injecto(s) or bad MAF sensor.

If you see low mpg on the test above buy a couple of bottles of fuel injector cleaner. Pour a bottle in the tank and at the next fill-up use the other bottle. This could bring an improvement to the situation and if so I recommend to use more cleaners, like 3 - 4 more of them with the following fill-ups to clean the injectors.

Personally I trust STP as a cleaner but there may be others. And I am not connected to the STP brand in any way so this is not an ad. I have just learned it works well.

Arrie

This was with my previous car the 2011 E350. I always use the highest octane I can find. In some stations it is 91, others say 93. I have learned that 93 or even 91 is not what they advertice in MOST of the gas stations. You can really feel when you hit a pump where the octane really is 93.

If you fill-up with lower octane you will loose fuel mileage 10 - 15%. I rather try to get the highest octane and pay that 10 - 15% more and get more mileage and POWER from the engine.

ddeliber

I used 91 the only two times I filled up! 93 wasn't even avail. I will try the STP, it can't hurt right? Frankly, I'll try just about anything that sounds reasonable.

moorewr

My 10 E550 (23K) gets 23.9 overall. I am a grandfather but 80 mph is ususally where the cruise is set and the car will produce around 26 mpg, I do check it at the pump and its always close, always use 93.
ron

Arrie

If your 2010 E550 gives you 26 mpg with 80 mph speed youy need to sell your car to the Mitshonian Institute! It would be an awesome show piece of what past normally aspirated V8 engines were able to do as the ones of the current time (20 years later) cannot come even close to.

moorewr

I must appoligize, I just went down to take a photo of the odo with the digital camera, the battery is down, but I did call up the data, and after 26K, (here my appology) it is showing 23 mpg, not as I stated 23.9, sorry for the mistake. ron

ddeliber

Not sure what changed, but over the past couple days I have seen a significant change in fuel economy. Just today driving in to the office I was at 21ish mpg in traffic and on the way home is was at about 25mpg (very little traffic) driving normally but watching. Compare this with last week where I was getting around 19 in and 21 home in similar conditions.

Am I magically driving more efficiently, probably not but what do I know...
is the car learning something?
did something "fix" itself (I didn't get a chance to get the STP)?

El Cid

I tested my onboard computer when first got car in 2010 by comparing it to number of gallons to fill vs. miles driven. Onboard computer read about 1 MPG lower than actually getting. Of course, using measurements at pump are variable also as to when it cuts off and how full tank actually is. I used same station and pump when I did my test.
My best ever MPG was 32 at 60 with cruise, windows up and AC off on the interstate. Recent trip I averaged about 28 on interstate at 65-70+ MPH with cruise on.
Your mileage will vary!
Ethanol cuts into the fuel mileage and it is about to go to 15% fairly soon.
One problem with onboard computer is that when you reset it, it defaults to about 22 MPG, so you have to drive some distance for it to start making up for that.
I have had cruise on 60 going downhill and with foot off accelerator and reset computer, always starts at about 22, even though the car is actually getting 50-75+ MPG.
BTW, I add Techron to the fuel every 5-7,500 miles. Dealer also does it when I take it in for service. MBUSA approves of Techron as an additive.
I frequently drive within a two mile radius of home with several stop signs and it averages about 17 MPG then. Never get over 35 MPH.