Terrible gas mileage on C300 6 speed?

[JaCkaL829]

Hey everyone,

New to the forum, joined to get some information for my cousin. He owns a 2008 C300 sport with the 6 speed transmission. It's a really nice car, he's got most of the options: 18" AMG rims, rear spoilers, premium package 2, etc. Anyway, recently he's been paying more attention to his MPG, and have been noticing that it's been awful. Last time he filled I believe he averaged 13.2 mpg, which has been the lowest. I believe the past two fill ups was around 14-15.

He really babies the car, never floors it/redlines it, race it, etc. He always uses premium 91+ gas. We are just kinda of baffled as to why he would get such bad gas mileage? He got the car brand new last January. It has about 3-4k miles on it. He drives almost 100% city, daily commute is maybe 1-2 miles if that. At first I was thinking maybe it was the bigger and wider tires/rims, or even thinking maybe it's not broken in all the way yet, but 13 mpg is pretty awful. I even checked his tire pressure prior to the fillup and topped them off to correct amount.

Just curious if anyone has any ideas as to whats going on. I'd rather ask people on forums before he goes to the dealership and gets jerked around.

Thanks!

[jstaneff]

Take a trip. Go somewhere where the car has to be driven at 65-75 for a few hours, then check the mileage. If it's still bad, then maybe the car has a problem. If the mileage hits or exceeds 27, then the problem is how he's driving on those city streets.

I'm driving the 7-spd, and I've seen 13 on a single day's city driving. Lots of stop signs, red lights, and such. Then I took the car on the road and hit 32. So some city driving can be bad. Mostly my city driving is at about 21 or so, but ...

These cars drink gas on start-off from a stand-still. They drink gas on the on-ramp. It takes blocks and blocks to get it back on streets, and up to 3 miles to get it back on the freeway. ("Get it back" here is defined as to recover the mpg reading you had before you tromped the loud pedal.)

[cvx5832]

Also, give it time to get fully broken in. I also noticed that horrible mileage in the beginning, but it gets much better.

Regards,
Paolo

[JaCkaL829]

Originally Posted by cvx5832

Also, give it time to get fully broken in. I also noticed that horrible mileage in the beginning, but it gets much better.

Regards,
Paolo

At what mileage is the car considered 'fully broken in'?

jstaneff: I was actually planning on doing that with him. Fill it up then jump on a highway and keep it at 65mph in 6th gear with cruise on for a good amount of time, then fill up again to see what kind of mpg he's getting.

[omgitselaine]

Originally Posted by JaCkaL829

At what mileage is the car considered 'fully broken in'?

jstaneff: I was actually planning on doing that with him. Fill it up then jump on a highway and keep it at 65mph in 6th gear with cruise on for a good amount of time, then fill up again to see what kind of mpg he's getting.

I take a drive down to one of my corporate offices near Philly like once a week and i'm crusing at 60 to 70 mph and i'd have no problem getting above 27 mpg and even hit 30 mpg once regular city driving with lots of stop and go id be lucky to go anywhere near the high teens

ps i've got the 4matic with auto

[jrct9454]

This is easy - look at the original question!

The car never gets warmed up....no wonder the fuel consumption is crappy. In strictly city usage, ours never gets better than 15 mpg....in our case, that is practically never, as ours spends most of its time on the freeway with the coolant and oil fully warmed up.

The suggestion to take the car out for a good airing once in awhile is a very good idea.

A gasoline V6 C is NOT an economical city car.....period. Your fuel consumption is precisely what I would expect it to be under the circumstances described.

[nyca]

Indeed, and the car is heavy, moving that mass from a dead stop is the main factor keeping MPG down.

So far, after 8 weeks ownership, I'm OK with the mpg on my 3004M. I'm getting just under 26 in 80/20 highway/city driving. One night last week on a particularly smooth trip home from work, at the end of the highway portion of my commute, the trip computer showed 28.1 mpg for that segment, that's the best I've done so far.

[C300Sport]

I do about 90% city driving with most trips under 5 miles. I have a good bit of stop and go and have been averaging about 19 mpg. Mine just got broken in (1600 miles in 3 months) but I really don't expect to do much better with a 3500lb car in the city. On my three road trips(between 80 and 120 miles each) I hit the upper twentys, with one trip hitting 31 as I was coming up the offramp.
13-14mpg sounds like a mechanical problem to me unless you are really sitting a lot in those short trips to the office. Take a cab the mile to work and get the car out on the highway...

[Derspeed]

I have a 6MT. On the highway I can easily get 27-30 mpg. I have to agree with JRCT9454. It's the city driving. 13 mpg still seems a little low though.

[C300SportFahrer]

Originally Posted by C300Sport

I do about 90% city driving with most trips under 5 miles. I have a good bit of stop and go and have been averaging about 19 mpg. Mine just got broken in (1600 miles in 3 months) but I really don't expect to do much better with a 3500lb car in the city. On my three road trips(between 80 and 120 miles each) I hit the upper twentys, with one trip hitting 31 as I was coming up the offramp.
13-14mpg sounds like a mechanical problem to me unless you are really sitting a lot in those short trips to the office. Take a cab the mile to work and get the car out on the highway...

I second this, I've only got around 700-800 miles right now and in town it isn't too bad, but highway (autobahn) it's upper 20's at average speed 75-80(it's still not broke in).
Shawn

[Untertürkheim]

This thread is relevant, some might find it interesting: 70 MPH cruising engine rpm

[AsianML]

Originally Posted by jrct9454

This is easy - look at the original question!

The car never gets warmed up....no wonder the fuel consumption is crappy. In strictly city usage, ours never gets better than 15 mpg....in our case, that is practically never, as ours spends most of its time on the freeway with the coolant and oil fully warmed up.

The suggestion to take the car out for a good airing once in awhile is a very good idea.

A gasoline V6 C is NOT an economical city car.....period. Your fuel consumption is precisely what I would expect it to be under the circumstances described.

I'd have to agree. Not only is it mostly city driving as the OP stated, but the engine never reaches operating temperature (1-2 miles isn't enough).

[Stick Girl]

Originally Posted by Derspeed

I have a 6MT. On the highway I can easily get 27-30 mpg. I have to agree with JRCT9454. It's the city driving. 13 mpg still seems a little low though.

+1 to this whole post. I get roughly 21-23 mpg consistently and I drive about 40 miles RT to work/home in sometimes stop and go traffic. I get much better on the highway.