Overfilling the engine oil - Nev
You are told never to overfill the engine oil but I am unsure what problems it causes if you do.

A friend has just had his 2001 VW Golf 1.6 serviced by the VW main dealer and it shows the oil level about 8mm over the max level. He contacted the garage who just shrugged and said don't worry.

Is the garage right or should he drain some out. He is a pensioner and so does not use the car that regularly.

Any thoughts

Overfilling the engine oil - carlh
I'm no expert but I believe it's possible that it could damage the catalytic convertor. 8mm over max seems quite a lot more.
Overfilling the engine oil - Mikey Jay
Overfilling the engine with oil does matter. Of course it is a question of degree. If the engine is severely overfilled it can blow up. It causes something called windage where the crankshaft froths up the oil. I believe that an overfilled sump also increases the crankase pressure and puts a strain on the oil seals. I am not an expert on this subject but some garages overfill engines,accidentally one hopes. If it is severe it is best to drain some out. A friend of mine has used a bilge pump to extract oil via the dip stick aperture.I dont know whether 8mm in Nev's case matters, but he is right to point it out to the garage and even take it up with VW technical dept. I would write a short letter to the garage manager. This could cover you if anything went wrong later. Might be difficult to prove it was the garage's fault, if engine damage did occur. Best wishes, Mike
Overfilling the engine oil - Sooty Tailpipes
Yes, a bit may not matter, like 1 or 2mm, as I'm sure there is that much safety margin, but 8mm is a definate overfill. Like Jay says, this whisks the oil in severe cases, and may cause excessive PCV oil spray being sucked into the inlet manifold. Also, in extreme situations, such as steep hills, or emergency braking, the oil might slosh more than the engine was designed, and the bottom of the piston might splash down into it and at the speed they move at the coefficient of drag would be phenominal.
Overfilling the engine oil - rg
There are stict instructions on an aluminium etched plate under the bonnet of my Vx Monterey not to overfill.

I recall that these 3.1 TD engines self-destruct if overfilled.

This was confirmed by an Isuzu indie.

(Can't recall what the phenomenon was, though. Are you there "Nene Valley Dizzy"?)

Overfilling the engine oil - Anglesey Ian
Ditto to rg.

I purchased my Saab 9.3 Tid in May of this year and recall a similar thread warning (about that time) of the dangers and catastrophic failure which could occur due to over filling with oil. Certainly my handbook contains at least 4 similar warnings together with a prominent warning under the bonnet.

Overfilling the engine oil - Dizzy {P}
Are you there "Nene Valley Dizzy"? >>

I'm always here, Rob! You obviously remember that we discussed this very subject before where I chipped in with the following posting: www.honestjohn.co.uk/forum/post/index.htm?t=13740&...e
Overfilling the engine oil - Cyd
Go back to the dealer and ask for the oil to be drained back down to the max mark (or 1 - 2mm below). Insist and do not take no for an answer - they really should know better.

*Blown oil seals
*frothy oil from crank windage (air pumped round with the oil)
*excess oil on the bores that the oil seal cannot handle = burning oil = knackered cat eventually (along with knackered oil seals probably).
*Broken big ends from the housing smashing into the oil surface each revolution
*and more........
Overfilling the engine oil - madf
In BL days they had a spate of ruined engines: only conscientious drivers mind you. Cause:? incorrectly marked oil levels on dipsticks on (IIRC) 1.8 B series engines fitted to BL 1800s . Those who never checked their oil were ok.. those who topped up regularly (overfilled) suffered from failed bearing due to oil frothing..
Overfilling the engine oil - Armitage Shanks{P}
SAAB diesels are certainly sensitive to overfilling and owners have been sent a very specific way in which to check the oil level. After a run and a 5 minute standstill on level ground one reads the level and the dipstick comes out with no oil showing on it at all! Wipe clean and dip again at once and the level shows correctly - still don't understand how that works!! However, if one acted on the first dipping and added a litre one would be well overfilled. I understand that diesels can in some way blow or pump X/S sump contents up into the combustion area of the engine where it burns without any control from the throttle and the engine can over rev and self destruct. I think this particularly applies to the GM engines fitted in SAABs, Fronteras etc. Be warned!
Overfilling the engine oil - Andrew-T
My 4-stroke mower's dipstick is the reverse - first check looks normal, a second one is way low. I don't know which I prefer!
Overfilling the engine oil - Andy G
I too have a 1.6 Golf (16 Valve) and this happened to me as well at the main dealer in Aylesbury, when they drained the oil to replace the oil sensor in the sump, then filled up without taking account of the extra oil in the oil filter that they didn't change. Or that was what I was told when I went screaming back again after I'd dipped it at home. The oil sensor wasn't faulty by the way, the combi unit (dash instrumentation) was.
Overfilling the engine oil - Nev
Thanks to everyone for all the responses. I think a trip to the dealers is called for.


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