AO Platinum Member
Join Date: Feb 2002
Location: The land that Time forgot
Re: Oil is black on the Dipstick ??
Oil goes black not when it "wears out" but because it accumulates dirt and rubbish from within the engine and as the by-product of combustion.
So, black oil could be new or it could be ancient.. though normally you would expect old oil to be black and new oil to be clear for obvious reasons.
I can think of three scenarios;
1) The car was filled with new oil. It could have been synthetic or a type with high detergent content and that has cleaned a lot of crud that was in the engine, going black in the process. That could suggest the previous owner may have neglected the beast in the past or run the oil to 12,000m/20,000kms as the book says. This is rather too long in my experience and you do get rubbish (carbon/gum/varnish) building up.. New oil would clean that off.
2) The beast is contaminating the oil. If it's burning oil, that could suggest a dubious valve seat or seal or at least one worn ring. That would let combustion gas into the oil and that would account for the black (carbon) oil. So.. check that there is good compression on the cylinders and that the car stops burning oil when the oil level is corrected.
3) The oil wasn't changed, though I find this hard to believe as it's the easiest part of a "service" to do and the first thing a client would check when they get home (clean oil on the dipstick). Get some oil on your fingers and squeeze it between thumb and forefinger. It should feel "thick" like cream, not "thin" like water. If it feels thick then it's new oil.
The over-fill should be corrected as it will be puffing excess into the inlet manifold and burning it off. This is enviromentally nice but it's likely to foul up your cylinders and potentially some sensors with gloop and crud. It also makes it difficult for you to work out if it is losing oil (see 2 above) or if it is just puffing out the excess...
Check the oil when it is cold.. forget the new fangled nonsense. Cold engine, flat surface.. first thing in the morning when it's been sitting there all night. Take the stick out, wipe it, put it back in, withdraw it again and that's the oil level (on the side facing the engine).
No bullets for Chaingun..