Glyn M Ruck

Dynamometer running tells me that it can take up to 8 hours to fully evapourate off all water & fuel contamination.

This is off course extreme as 80% can be removed in maybe 2 or 3 hours of hot running.

Sounds like a big proportion is water. One week of cold running and numerous cold starts can get water levels up around 8% - once again dynamometer proven.

I recommend you give the vehicle a weekly hot run or reduce your drain interval.

contact148

Thanks Glyn

after work today i let it idle for 10 mins then i took it for a 30 mins drive at 80kmh except for lights and traffic outside temp was at 0

I do plug the car in which gets it to 40 (lowest # on the temp guage) in about 2 mins of driving otherwise it can take 10 mins to warm up that far

the timmer turns the block heater on for 3 hours before i leave in the morning

Glyn M Ruck

Stop the 10 minute idle if you do that often. As soon as the engine is stable get moving without demanding full power. That idle will make matters worse.

contact148

it was just today usually its less then 1 min idle

Glyn M Ruck

OK

contact148

well went for 40 min drive stayed there for 1.5 hour then drove home constant 120kmh engine fully warmed outside temp 1c

oil level remained the same I was hoping it would have dropped.....

RLE

This is an old favorite false alarm for W203 owners. My C320 used to show this warning and at first I was in a panic about coolant leaks into the oil etc.

The dealer fiddled around with the level sensor but finally changed the measurement parameters and the big red warning went away, never to be seen again.

You DO NOT have a problem that needs immediate attention and since the car is out of warranty you will have to decide if you want to pay for a fix.

Glyn M Ruck

You obviously did not read the whole thread. This car has a history of rising oil levels & oil tested at 6% fuel dilution.

mleskovar

After looking at the Blackstone report again.....no water, no glycol, 6% fuel. That and the fact you get terrible mileage. Maybe it's time to use a boroscope and check out your cylinder walls for witness marks from a broken ring(s)? Just guessing here, but SOMETHING ain't right.

contact148

I doubt its rings car starts and runs perfect

the fuel problem ONLY happens when its winter (im in ontario canada)

today with cruise on set at 120kmh i drove the whole 40 mins both ways no stopping or traffic

milage was at 11.8L/100km and dropping my car is a 4matic and i have snow tires on roads were clear today no snow tranny was in S mode summer I recall getting 8.9l/100km

I do know they do somthing to the gas here in winter as winter milage allways drops (we had a week of + 7c and milage still sucked)

I use shell 91 or costco 91 i ran a bottle of techron last year but as its not available in canada i cant do it often

mleskovar

Glyn is sleeping so I'm offering my guesses..

Gas it getting to the oil. How else would it get there?

Unless there's an additive that sneaks gas into the oil I don't think they make a difference for the excessive presence. Gas mileage certainly but not 25% like you report.

contact148

thats the questions now isnt it how the F... is gas getting in my oil

It ONLY happens in winter

I had the injectors cleaned and tested (removed from car and done in a bosch machine) saw them under pressure NO leaking.... maf sensor cleaned

NO pending codes
133,000 km

I now put about 12k a year on it

maybe the gasoline fairy visits each night, Now all I need to do is show her gas goes in the gas tank NOT the oil sump.....

mleskovar

Or someone installed oil that glazed the nicasil coating or ring faces and when it's cold it allows a lot of blow by. Is that possible? (Glyn probably knows). The question still remains....how many paths to the oil can fuel follow? PCV valve?

Glyn M Ruck

The gasoline has no trouble passing good rings, neither does silica, water etc. As a piston changes direction at top but mainly bottom of stroke the rings unload & bypass is normal. All rings suffer leak past.

The sources of fuel in the oil are generally: over rich running, incomplete combustion, dribbling or leaking injectors. We've done the injector check although there could still be a problem there.

Winter fuel in Canada will be less dense with more light ends to aid cold starting & will give worse mileage.

I think the main cause of this issue is the duty cycle this car runs - never fully warmed up for long enough in winter to evapourate off fuel & water. My C240 suffered zero fuel or measurable water dilution but running in a moderate climate on different fuel & longer trips with less running under enriched mixture conditions. The oil level measuring device was always fine.

The oil sample might not have been representative either. Water assumes two forms in the sump. Free water & water in suspension in the oil. Dependent on temperature if the water loading becomes too high it will phase separate & sit on the bottom of the sump with the oil floating on top of it. I'm still surprised to see no water in the Blackstone sample as during the warm up cycle the light ends of the fuel should evapourate off before the water.

In Dyno testing for research over 10 & 20 kilometers from a cold start - testing at 6am, 2pm & 10pm in a daily cycle we could see water level in a representative oil sample taken during warm up with the engine running at between 7 & 9%

I think there are lots of cars in very cold climates that run with high fuel & water dilution - people are not aware of it because they don't have Benz sensing capabilities.

Diesel contamination of petrol is another thing that can cause rising sump levels.

I recommend that contact148 tries to do at least one longer fully warmed up trip a week & monitor. Also try running the block heater every night for a while. If this does not help then shorten oil drain interval in winter. Also try filling at a different service station for a while.

BTW - 8.9l/100Km's is about the best a C240 can ever do. In gentle driving fully warmed up in a 40Km trip 9.3l/100Km would be more normal on a RWD.

contact148

Thanks glyn

your info is VERY helpfull

starting tonight ill have the blockheater timer set to come on at 12pm I leave at 8:15am so that will give me 8 hours Im going to double my trip to work from 7 min drive and maybe 5km to 10km by going the long way

I still have my 93 acura legend that i have had since new it has a 6cyl engine and warms up in 3 mins in this temp I could allways drive it to work too

At least the benz warms up WAY faster then my 1946 ****** jeep and the benz has a top and a heater too.......

ill keep this updated im going to check the level daily where i park in the exact same spot.

contact148

Glyn

got to checking the level yesterday where i allways check it and after my 40mins each way drive the level was DOWN .4L which is 400ml

so you are CORRECT it seems i need to drive it longer!

Glyn M Ruck

Good news - just watch it over a period of time & the block heater will also help.

EDIT: And remember 1.03 gallons of water are produced per 1.0 gallons of gasoline burnt at stoichiometric.

Which is why we usually say in the oil indistry that burning a litre of fuel produces a litre of water - or burning a gallon of fuel produces a gallon of water.

Most of this goes out of the tailpipe in the form of water vapour but some gets past the rings into the sump. This is made worse at very cold start & in rich mixture conditions that are way off stoichiometric.

Plus we have some fuel not being fully combusted under rich mixture running conditions & of this too some gets into the sump.