We do a lot of oil changes at our shops. Maybe not as much as the quick lube places (we don't purport to be a quick lube by the way - we handle a lot more than just maintenance), but enough to see some pretty crazy things come out of an oil pan when the drain plug gets removed. There are all kinds of invaders that can get into your engine oil and wreak havoc. In some scenarios, the oil comes out looking like dirty water when coolant of fuel gets mixed in. Or, it can look like the chunky mushroom soup if water ends up in the engine crankcase. Often the oil will reek as it mixes with liquids that just aren't supposed to be in there. If, while the oil is draining, you shine a flashlight on the stream of crude it will appear shiny as tiny flakes of metal sparkle in the beam.
Is this normal? Yes...and no. All engines, transmissions and the like are dealing with metal parts working in conjunction with one another as they go about the business of propelling of your vehicle down the road. The oil in the car's engine is meant to form a barrier between one part and another and additionally, suspend dirt and metal so that the wear and tear on the moving parts is minimized. It is important to understand, because we get asked a lot, if oil needs to be changed even if a car isn't driven? Yes, because it is still acting as a cleaning agent on those metal parts, holding the dirt like Aunt Shirley's Jello mold held those pieces of pineapple back in 1977. But, the metal parts do still have some contact, and because of the workhorse that an engine is, the metal is worn down and the result is metal particulate in the oil. When we rebuild engines, we have to change the oil after 500 miles of use the first time because there is an excessive amount of metal in it from the machine work that occurred when it was built. However, when the oil is old or low, and is failing to protect the machinery inside the engine, the amount of particulate also becomes excessive. It is sad when we have a car come in that is making all sorts of motor noise and we pull the drain plug and it looks like a gold rush, a 19th century miner's dream. That engine has cashed in it's chips and is looking forward to retirement. That is why it is critical to make sure that the oil stays continually full in the crankcase, and why every owner's manual says to check the oil regularly and top it off. We have some customers who, every time they come in, we have to make the note: oil was low prior to service. We know it is only a matter of time before that engine starts knocking.
Now, the picture associated with this post happens to be from an engine that, unbelievably, was still running when it came into our shop. This was an older engine off a Jeep that had been having some noise issues. But it was still incredible to pull the oil pan off and discover huge chunks of piston, rod and bearings littering the container. No need to pull the plug on that one to check for metal particulate, that was present thousand of miles ago!
So, check the oil regularly and keep it in the safe mark of the dipstick. We work on numerous Subarus and almost all of them have engine oil consumption issues. We tell our customer base to consistently check the oil level and top off as needed but it doesn't always register with them until the engine replacement bill comes due. Don't be that Subaru owner or that "any-car" owner. Don't know how to check the oil? Stop on by and we'll happily show you!