Sooty exhaust poor mpg

[Ridleyrumpus]

I have a 2009 E320 tgat I bought a few months ago, 135k.

I have noticed it is giving my poor mpg, low 30's if I am lucky. Around town it's low 20's. This is much much worse than I hot in my old E280, I know this one has a bigger engine but not that much bigger.

I have also noticed that the exhaust pipes are thick with black spot.

I can't help thinking are the two related? If so where should I start looking?

 

[onefortheroad]

If it's the V6 with 7g gearbox, low 30's is about as good as it gets tbh. Things to check , Maf , O2 sensor ( well known failure on this engine ) , air filters are clean. Best I ever saw was 37 mpg over a good motorway run , 08 CLS 320

 

[Ridleyrumpus]

Understood.

But why is the exhaust so sooty, it's defo not normal.

 

[onefortheroad]

I just gave you 3 possibles as to why !

 

[Blobcat]

Boost pipe leaking is another

 

[LostKiwi]

Boost pipe leaking is another

Yep. Quite common.

We get mid twenties from the R350 (very similar engine) and have seen over 42mpg on a trip though more usually around 35-37.

I would expect similar from yours.

 

[V6Matty]

That is low for your car, not too much but certainly down on where it should be. The others have noted a few things that are likely the culprit of that and the sooty pipes , my money on it being the split boost pipe, notorious to go after the O2 sensor and you end up over fuelling.
question though, has it always been that bad or it more recently happening?

 

[malcolm E53 AMG]

When you’ve checked the suggestions above make sure the engine is getting up to temperature ie 90 degrees if not the ECU will enrich the mixture hence the poor mpg, if the thermostat does need changing better to buy OEM aftermarket can be problematic

 

[boxer 01]

My exhaust tail pipes were always really sooty and but after replacing the O2 sensor they are not as bad, also improved the mpg slightly although it wasn't too bad to start off with. What did improve the mpg was the inlet manifold decoke I did when I did the oil cooler seals last year.

 

[Flyinspanner]

Petrol 320?
those mentioning a boost pipe - I don’t think the petrol 320 has a turbo, so no boost pipes?

 

[Ridleyrumpus]

Petrol 320?
those mentioning a boost pipe - I don’t think the petrol 320 has a turbo, so no boost pipes?

Diesel

 

[markben]

Different model (S320L cdi OM648 inline 6 engine @140k miles), but if it helps:

I had a similar issue with sooty exhaust tailpipes + dark smoke on hard acceleration. Fuel economy great, 33mpg in town, up to 46 mpg on a long journey, plenty of power, no misfires or starting issues. At first I suspected a clogged DPF, but discovered that I don't have a DPF on my car, so that wasn't the problem! Oops!

On another forum, a couple of ppl suggested either switching to Premium Diesel (with extra additives to clean out injectors etc) or using an additive at each tank refill with regular diesel.

And / or:

Giving the car a long, fast run regularly to 'blow out the cobwebs' (my daily routine is usually pottering around town on short journeys at low revs in higher gears, and due to bags of low down torque, rarely needing to go above about 2000 rpm).

I switched to premium diesel for a few tankfuls + gave the car a good 'stretch' more frequently and Hey Presto: less soot and only ever a little pale grey smoke on hard acceleration. A dramatic difference... and mpg as good as ever.

My best guess is that, assuming your V6 320 cdi engine (+ on yours, the DPF) is healthy with no other faults, it might (stress might..) just need better quality diesel fuel + a good, long-ish, fast run regularly to let it breathe properly. These high torque (at low revs) cdi engines do like to get some proper exercise and stretch their legs - a bit like a Racehorse?

Maybe worth a try?

 

[Botus]

I have a 2009 E320 TRACTOR I bought a few months ago, 135k.

I have noticed it is giving my poor mpg, low 30's if I am lucky. Around town it's low 20's. This is much much worse than I had in my old E280, I know this one has a bigger engine but not that much bigger.

I have also noticed that the exhaust pipes are thick with black spot.

I can't help thinking are the two related? If so where should I start looking?

would help to state its a diesel tractor...

the 280 is the exact same engine - I think its just a smaller inter-cooler and less boost

my fathers 280 CDI does 25 round town and 42 on a steady motorway run

ave 32 at best or 27 if most is round town and you drive like a cabbage