The engine oil Bibles, covering everything you need to know about engine or motor oil including viscosity, friction reducers, additives, oil types, sludge, SAE and API classifications and ratings, what all the codes and markings mean, how your engine oil works, how to keep your engine running at peak fitness and much mode.
![[engine oils]](images/sludge.gif)
A Case Study
In January 2007 I was contacted by a reader (Mike) with a curious problem. As he described it, "small 'flakes' on the dipstick....that disappeared when rubbed between my fingers". Not entirely sure what to expect, I asked if he could take a photo and email it to me, which he did:
We figured out pretty quickly that Mike was seeing sludge on his dipstick. This was a dilemma because he'd only just bought the car - a Saab 9 5 Aero with 42,000 miles on it. At this point Mike had one of three options open to him. First, take the car back. Second, let his dealer take it to their regular mechanic and let them sort it out. And finally, get Mike to take it to his own mechanic who he trusted, but that would absolve the dealer from any further responsibility to damage caused by this situation. Whatever happened, the sump would need to be dropped and the engine would need flushing.
I recommended that Mike go with option 2 and that he go along camera-in-hand to document what the dealer mechanic found. For those of you with a Saab, this is what can happen when you succumb to sludge. Click on the pictures for larger (1600x1200) versions:
The second image shows the most worrisome aspect of sludge in this case. The oil pickup that dips into the sump is covered with a mesh strainer - not unusual. The sludge has peppered the strainer with little clumps and reduced its capacity to pick up oil. This can lead to a starved oil pump which in turn would normally lead to reduced oil pressure and capacity in the upper part of the engine. The end result of that is usually a seized engine - where the metal parts rub together with no lubrication and basically weld themselves together.
Mike's Saab 9 5 Aero is now sludge-free, and hopefully will stay like that with regular, decent oil changes. At least the problem was caught early and resolved. If you want a true horror story, you need look no further than this page to see what happens when sludge isn't caught early on.