Just picked up an s class Saturday and drove it 180 or so miles back home from the dealership and only averaged about 20 mpg. The car is rated for 26? What's going on here? Is something wrong? Should I call the dealership?

 

I doubt there is anything wrong.


I put on 16000 miles on my '14 S550 4matic before it was totaled in an accident. The highest mpg I received on that car was 25.2 mpg in an 1100 mile stretch from PA to FL.


On my '16 S550 4matic I believe the best I have done was 25.5 on a 6 hour stretch from PA to SW Ohio.


Both these times I had the ECO Start/Stop on and in comfort mode.


If you use sport mode (which I use most of the time) with the ECO Start/Stop off you will never achieve 26 mpg. In fact most of my driving the a combination of city/highway driving is about 14 to 16.5 mpg. There is a big range of mpg on this car depending on how you drive such as quick starts,etc.

 

Its all how you drive. Did you purchase New or Used? You can do a reset of the transmission and it will adapt to your driving style. Make sure you are using Premium as recommended and that your Tire Pressure is at the recommended setting as well as a clean air filter. Just some basic info if you purchased it used, never know how the car was cared for or maintained.

On a trip from Ohio to NY, I averaged between 26 - 29 all highway mostly flat roads. AC on, not in sport mode and no Cruse Control. With Cruse set, MPG dropped a bit but on flat roads and no heavy winds, it is possible to see 26 to 29.

 

Personally, on highway driving my experience is similar to Nice Ride's. That is when averaging maybe 67-72mph. If the OP lives somewhere where the speed limits are higher that might explain some of the mpg difference, but to me 20 mpg does sound awfully low if all highway.

 

New owner here as well and only have ~225 miles on the ODO with 90% being city driving. I am currently getting 14.7mpg over my total miles. I am a bit surprised it isn't closer to ~18 which was where my 2011 E550 was in the same driving conditions. It would get 24-25 on the highway but I would typically run 80mph or better for those trips. I am chalking up the poor mpg to a tight engine that will improve after the break in period. Not to mention this is a HUGE vehicle. As others mentioned, using premium vs plus or regular makes a huge difference.

Then again....I didn't buy this car for MPG or I would be driving a Prius / Volt. No sarcasm to the OP intended or implied.

 

Your 14.7 mpg is not surprising to me.


My last tank of gas my average was 13.86 mpg at 14,500 on the ODO for my '16 S550 4matic. Some of those days however were below zero temps in city traffic. The car is a gas hog in city driving especially in the winter.

 

Do you thing 2 of the reasons in Cold Weather and Lower MPG would be related to: 1. Ethanol in Fuel during winter months and 2. Cooler air, more air more fuel with the turbo's? Compressor is more than likely running less which should add about 1 to 1.5mpg.

 

Frankly, I've never checked the mpg I am getting. That said, my feeling is that city mileage is horrible, while highway mileage seems to be great, which seems to be the case with others here.

 

The numbers reported above are an unpleasant surprise. I have a 2007 CL550 which has the non-turbo engine and on a recent trip from Southern California to Las Vegas at 70MPH almost the entire trip and got close to 28 MPG. On a 90 mile trip to San Diego, I had 30 MPG. The current turbo engine is claimed to provide better mileage than my engine. My vehicle weight is within 100 pounds of the current S550. I am only able to achieve these mileage numbers going at a steady speed. Mileage drops to about 24 MPG with minor traffic slowdowns on the freeway. Stop and go city driving can reduce it to as low as 16 MPG. Also, California uses a unique gasoline blend for air pollution which has a lower energy content than gasoline available in the other 49 states (and is more expensive). My vehicle has 19" wheels.

 

2 things could be affecting it:
1) brand new engines typically don't reach optimal mpg for a few thousand miles.
2) your wheel size. Smaller is better for mpg. Pretty sure they conduct mpg estimate tests on the 18" wheel equipped vehicles vs 19" or 20" examples.

 

On my '17 S550 I average 20 mpg in mixed driving in the summer and 18 mpg in the winter. Also, this is my fourth S class and I've noticed that mpg when the vehicle is new improves significantly over the first few thousand miles of driving.

 

It was new. The gas tank was filled by the dealer and I'm assuming they put premium in it.

 

My '16 S Coupe's city mileage was dismal even while driving gingerly and after break-in. I'll be interested to see how my new '17 does with the 9G.

 

My 2015 S550 4Matic, which I've had for 4 months/5k miles is also struggling to get anything close to the ETA estimates. My BEST so far is 24MPG for a 1 way trip (averaging 70mph, steady speed, 2 passengers, no AC), the total for the tank averaged 20MPG 95% highway, which is also the best I've seen so far. It's a CPO car with the AMG sports package and wheels. I got it with 15k miles, now has just over 20k miles. These numbers are from the onboard computer, the numbers i calculate from the pump are about 15% lower. I record all my cars/motorcycles at every fill-up or service with "My Cars Pro". I typically get above the EPA estimates and can easily see the seasonal ups and downs as the temperatures and fuel changes happen.

For example I was routinely able to get between 70-80mpg with my Gen 1 Honda Insight. On my recently sold-back VW Passat TDI I was able to get 35mpg in city and 50-60mpg highway. My GTR gets 17mpg in mixed driving but the motor isn't broken in yet at 4k miles. I can get up to 35mpg (full tank) highway with my Lotus Elise.

I just bumped up the tire pressure on the S550 to 38.0F 39.0R, which was up 2 PSI all around to see if that improves the MPG.

I'm wondering if the lower MPG numbers are due to a "lumpy idle" that I reported to the dealer. They applied the SW patch per one of the service bulletins, which slightly helped but didn't eliminate the problem. Now the car has a little bit of a buzz at idle and now rarely has the lumpy idle. I personally think there's a problem with either a fuel pump or an injector but since there are no faults the dealer won't do anything. I exclusively use Chevron 91 octane and drive in San Jose traffic.

Anyone else seeing low mileage and rough idle? Anyone think these may be associated?

P.S. I have noticed that using the Distronic Plus is not the best way to get the best MPG, it's actually quite bad, accelerating and braking much harder than I would. Best MPG has been with it off.

 

I don't mean to belittle anyone's concerns here, but if you are driving a W222, is fuel economy really an issue? Average lease payments on our luxo sleds is what? Like $1,600 to $1,800.00 a month? For probably under $300.00 a month, we could be leasing a beautiful Honda Accord, which would deliver truly exceptional economy, but we have chosen not to. Personally, I have never checked my MPG, as it just seems to be within reasonable parameters for a big, very luxurious sedan that will blow the doors off of 95% of the vehicles on the road. I'm content to leave it at that.
Merry Christmas to all,
Streamliner

 

In my case it's not about the $ but having to visit the filling station so often. Yes the power of M278 is awesome with actual stock dyno #'s of 474hp and 566trq. I think the new 4.0 will match the hp but will get no where's near this monster trq in non-amg form.

 

Ditto, gas station is one of the main reasons we got the S550e (Plug-in Hybrid) to replace our E550 (M278.) The S550e is my wife's daily car to the office...

In the crazy traffic Bay Area here, without lining up at the gas stations ever so often is a big time saver.

Now my wife can charge her S550e at home and at office, without worry about lining up at the gas stations. (As a plus, the S550e also qualifies for the California sticker, so she can drive on the commute lane.)

We love the S550e. The silent/torque-y/smooth electric mode fits the S-Class very well. The E-mode ride is absolutely quiet and smooth, yet when the gasoline engine kicks in the combine power is more than enough for a daily drive (0-60 in 5.2 seconds.)

 

Sweet

 

Streamliner,

Not taking any offense about worrying about the fuel economy... however MPGs are a good indicator of the health of your car. Since I bought the car, albeit as CPO, I'm interested in understanding it's baseline MPG so in the future if there's a problem it could show up as a decrease in MPG. Since I'm monitoring it, the difference between claimed MPG and actual based on fule pumped and miles covered raises a question about the current health of the motor, hence the reason I asked about the rough idle and the idle buzz after the dealer applied the patch for the service bulletin.

I do wish I could have found a 550e with the same equipment since I would like to visit the gas station less than once a week. In my TDI it was once every 4 weeks, getting 700-800 miles from a tank. When I ride one of my motorcycles, sadly, its about every 3-4 days, but I lane split and save almost an hour of commute driving every day. Luckily the gas station is directly on my way home so it's not a big problem to deal with.

While the HP and torque of the S550 are nice, I didn't buy the car for that. I got it for the self drive in the stop and go... it actually works very well below 20 mph! Oh, and the massage and luxury, and the fit and finish (all unmatched!) and the massage and heat/vents in the back seat when I take my daughter places were almost a requirement

I love this car for the driving isolation, quality and comforts. However, it's also the slowest car I have

-Richard

 

Richard,

What exactly is going on w/your engine idle?

 

When the motor is warm, occasionally the idle will jump up and down by maybe 50-100 RPMs (it twitches the tach needle on the screen). More importantly you can feel the car shake left/right as the speed changes. It used to do this a lot more but as I mentioned, the dealer applied a SW patch from service bulletin LI07.08-P-061035 MAR15 – 222 (found the reference on this site!). That has greatly reduced the idle shake but I can now feel a buzz-like vibration at idle that wasn't there before the patch. So I've basically traded one issue for another one (albeit a less bothersome one).

When the car is in ECO mode, which is most of the time, the engine shuts off so there's no problem, but when ECO is disabled then it's there and bothers me, although my wife doesn't seem to mind or notice it. Since the S550 is my daily driver, I think I have become hyper aware of it.

Dealer says they can't do anything since there are no fault codes.

As an interesting comparison, when I bought my 2015 GTR, I took it in for the 1000 mile check/service and the GTR tech noticed the idle was off and the engine was running rough. I felt/saw nothing, but he replaced the spark plugs and a cable and sure eough, it ran even better when I picked it up. Granted, the GTR is a halo car for Nissan and they have 1 dedicated tech in approved dealers, but I sure wish the Mercedes techs were as aware of problems as the GTR tech was.

-Richard

 

I have an E350 that is a 6 cylinder car. I got 33 going and coming back from Florida and Last September I got 30 going and coming back from Myrtle Beach. Best car I ever had for gas mileage. And that is going 75 -80.

 

Where do you feel the buzzing, in the steering wheel?

 

Steering wheel and seat, although I haven't paid much attention to see if it comes from a particular area. Since it started after the SW patch, I'm assuming it originated in the engine bay. It's like the car has a high frequency vibration all over.


Happy Holidays!

 

Not normal as most can't even tell if their engines are running at idle.

Happy Holidays to you too