nvestr

Hi guys,

I now have 1800 km's on my C450 and I'm getting some pretty low fuel economy, much lower than expected and light years away from EPA ratings.

Even when I drive like a grandmother in Eco mode, I still don't get good mileage.

My experience, based on looking at the Consumption screen, which indicates L/100km fuel consumption for every 60 second interval. My commute is about 20 minutes, with the first 6 minutes or so being in stop start city driving. The last 14 minutes is freeway, about 110km'h (70MPH ish). It seems like the vehicle is sucking fuel hard when the vehicle is first started and eventually the consumption bars start to stabilize to where they should be (around 9 L/100KM)...

The problem with that is by the time I get to my office, most of the drive was spent burning a lot of fuel... It seems like you have to go on really long drives to get decent fuel mileage on this, as the first 10-15 minutes is uneconomical...

Is this the ECU mapping to protect the engine while it is warming up by sending a rich air/fuel mixture? Temperature was warm here today (around 70 F) and my engine was at operating temp in no time, say 3-4 minutes... It seems like it is leaning out the mixture way too long after startup, which is killing my mileage...

Anybody have any insight into how this works or is mapped?

My average fuel economy is 13.5-14 L/100... not good at all, much worse than my previous vehicles and my previous vehicle's EPA ratings were worse than the C450 so it doesn't make sense to me...

I feel like my dealer won't be very helpful when I approach them, so trying to arm myself with info beforehand...

lbowroom

When my 450 was brand new and I was flogging it I would get in that 14l/100km range that you're getting. I'm over 4000km on the clock now and have been averaging close to 10.2l/100km with conservative driving 90% of the time in Comfort occasionally flogging it in S+. Doesn't seem to matter that much which mode as long as not heavy braking and stop and go. Fuel economy came way up after 3000km's

tivoboy

So, I have noticed this as well. I'm getting about 21 MPG in combined driving (USA numbers) without doing a whole lot of hooning at all. on the highway, if I reset and try to keep it at 65mph, I think I could get about 26-27, but not 29. I don't see how 24 combined is possible at this rate.

Obviously, everything comes in to play. AC use, 75 mph on highways, stop and go, etc.. but it's not where I thought it would be at 2400 miles.

lbowroom

I don't think any car actually hits its EPA estimates. With the exception of VW diesels and Prius. They are meant for relative comparisons between models. I hope no one bought a C450 for its fantastic fuel economy....

nvestr

Definitely not expecting EPA numbers. I was, however, expecting better numbers than my previous car (2012 Acura TL AWD). EPA has much higher ratings on the C450, so one would expect a relative improvement. My TL was averaging 11 or so with my type of driving... this one is much higher as stated below.

Will keep an eye out as mileage improves but still find it weird that it's so thirsty the first 10-15 minutes of run time...

Shadwell

Check the basics;
Tyre pressure
Tyre wear (alignment)
Brakes binding

If these are all to spec, once the vehicle is run in then measure actual mileage (record fuel in over miles etc).

Then if still substantially over expectation approach the dealership...

Some people also live in very hilly areas, have heavy right feet, run lower octane fuel, always run the ac or electrical heaters to the max... All these need to be realistically factored...

EPA plus 20% is apparently considered normal...

Best of luck, hope it settles down or you find any problems...

hans007

if i keep it at 65 and drive my F30 sanely i can get about 34-35mpg which is what its rated for.

that said, i don't think anyone buys a c450 for fuel economy and i'd be more than happy with 21 combined when i get one (c43 coupe anyway).

i'd imagine the 9 speed might help a little bit, but yeah if you don't drive like you are on eggshells almost no car gets epa milage other than diesels

Cosworth2000

My car even with the transmission issues was getting around 11-13.2/100L KM but I believe it should get better as the engine breaks in more since it's under 1500 kms right now. As of today it's in the shop and not sure when I will get it back working properly.

On another noted, yes I noticed that it sucks gas however since we have digital readings and not analogue its not easy to really gauge the fuel use per tank.

tivoboy

I will say that our last C300 got great mileage, above EPA and more like 29-30 mpg on highways, similar speed and distance. We would get about 24 combined.

even with the higher performance of the C450, I figured the 7speed (which I did have in the C300 as well) and the SS and some other elements would at least get me similar or close to EPA for the car. Sadly, I'm running about 15-20% BELOW EPA ratings on the car at this point.

Jay_Chicago

I'm getting 35 mpg (6.7 L/100km or 15km/Liter) combined on my 2015 C300 in Comfort mode. My everyday commute to work is about 5 miles city and 12 miles highway. I think this is about average for C300.

Cosworth2000

Yeah, the C300 gives back amazing fuel milage. I have one as a loaner and was surprised how smooth and refine it is. It's so comfortable and great on fuel and yet still has an amazing get up and go in Sport + mode. Damn, I also feel like trading in my C450 for the C300.

cenzo86

I came into this car with the understanding that my fuel economy would be much worse than my last car. I'm finding myself driving at higher rpm in lowers gear than I should be just to hear the backfires. I usually do very short trips everyday so I'm expecting to fill up my tank twice as often.