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richy_uk

C63 Oil Myths

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Probably one of the worst features on the C63 is the oil dipstick. Difficult to read accurately and picks up oil on the stem as it's drawn out of the holder, it really is a bit hit and miss to know how much oil is in the engine. I resorted to Googling this topic and to be frank, read some complete and utter bollox (IMHO). The best (worst) was the notion of overfilling an engine with oil by as much as half a litre could result in it blowing up with the heat expanding the oil. What a complete moron. I get the fact that overfilling can damage cats etc etc but exploding engines, come on. Due to this stunning piece of advice, several owners (glad to say mostly American) pipe up in agreement with various theories and approaches slightly underfilling to avoid this catastrophic risk and its always better to run an engine on the minimum oil mark.

 

Being a bit chicken and not wanting to pile in and claim they were all in fact stupid and should have their car keys immediately removed, I decided to gather my own evidence. Every car I've ever owned, I have always done the same thing with regards to oil. First thing in the morning before starting the engine, check the level and top up to the max mark. All the oil should be in the sump and stone cold. Top up to max, then off you go. Simples ! Never ever had a problem doing this. In fact, I've always noticed fuel economy improved, engine is smoother and for some reason with auto boxes, gear shifts seem smoother too.

 

So, with my recent service, I supplied 2 x 5 litres of Mobil 1 and the dealer handed me back exactly 1.5 litres. So I know my car has the exact amount of oil. Next morning, I check the dipstick and it's bang on the max mark. So even if my engine explodes due to slight over filling, it won't be my fault as the last people to fill up the oil was MB themselves ! The moral of this story is that the internet is a worrying place with scaremongering bull$hit (especially from America). Cars are inherently designed to deal with the stupidity of the general public and you have to do something really drastic for it to go very badly wrong, that's unless you live in America where things go wrong regularly and legal action is taken more often than me going to the toilet.

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Is this a good place to admit my bonnet rarely gets opened between services?

 

(And no, that is not, however appropriate it may sound, a euphemism),

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Nor mine Garcon. In fact, I need to check the tyre pressures far more often too. The only reason I open the M3 bonnet is to clean out some side filter things or to top up the washer reserve. The headlight and screen washer dispenses about a gallon of water each time so you get to use that once between fills!

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Indeed, the Internet is not always a place of wisdom.  

 

dilbert2006114659027-1.gif

 

In any case, the damage caused by oil starvation is going to be catastrophic compared to the "damage" caused by overfilling - chances are any excess oil will just be burnt off.  Oh, wait, I've expressed an opinion on the Internet, I'm probably wrong, then  :bike:

 

Is this a good place to admit my bonnet rarely gets opened between services?

 

(And no, that is not, however appropriate it may sound, a euphemism),

 

You're probably ok with that here.

 

Not a euphemism....? yeah right  :rolleyes:

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I have always kept the oil in all my cars at the max mark. They get driven enthusiastically so want as much oil, to absorb as much heat as possible. Probably makes naff all difference but always made me feel better. Engines have breathers in the oil system to allow for overfilling and excessive pressure in the crank case.

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It's not pressure in the crank case that is the problem with overfilling oil, it's the physical act of the con rod big ends smacking into a pan of oil, the constant slapping can do a lot of damage, normally they are sprayed with oil on a high performance car, or have oil constantly running over them on a normal 'cooking spec' engine, and not actually sitting in oil.

 

I've seen damage done by overfilling, cracked bearing carriers and big end caps, and it is real, however, you'd need to put considerably more than half a litre extra in to get anywhere near doing any damage, especially on a car with an 8.5L capacity.

 

We had it on one of our cabs, driver checked the oil and it was on the minimum, so looked in the book and saw 5 litre capacity, so put 5 litres in, most dipsticks show a 1 litre range, so on the full mark, the car has 5 litres, and on the minimum it has 4 litres, so it now had 9 litres of oil in it when it should only have had 5.

 

It was fine (apparently) for most of the day, it was when he went on the dual carriageway at higher engine speeds that it all went wrong.

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Is this a good place to admit my bonnet rarely gets opened between services?

 

(And no, that is not, however appropriate it may sound, a euphemism),

 

Guilty as charged y'honor. :(   I think I checked it a few months back, just before the service - and none had been used.  Will check it again this weekend. :)

 

 

I remember my old man overfilled the car once, and he produced a large smoke screen as we drove home.  Soon disipated and the car was OK after that.

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One of the biggest issues of overfilling the oil in a modern car is the risk of damaging the cats if the oil is burnt

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