About a month ago I changed the oil in my Peugeot 207 and since I had all the tools out I decided to change the oil in the mower also. (The mower is a B&S 650) I collect all the used oil in an oil extractor that I made. Yesterday I decided to transfer the used oil to another container to take it to the recycler center. I poured the oil in a new jug and when I looked inside the old jug, in which the used oil remained undisturbed for over a month, I saw very little pieces of what I thought it could be sludge. I added a small amount of paint thinner and poured it in a piece of white paper, after the thinner evaporated what was left was undoubtedly sand or dirt. The biggest grains were about 1 or 2 mm in diameter and if I press on them they crumble into a very fine dust, some photos below. When I changed the oil, first I suctioned the oil out of the Peugeot, first trough the dipstick then out of the oil filter assembly, since it was the first time I was changing the oil in that car, I didn't knew if the suction method would get all the oil out, so I removed the oil plug and about half a liter came out into a clean pan, then I suctioned the oil out of the pan. After that I suctioned the oil out of the mower through the fill hole and it went into the same jug. So what could be the origin of this sand???? I really doubt it comes from the Peugeot since the filter should had caught all the debris and I didn't saw any sand in the filter housing or the filter itself. (Although I wasn't looking for). And the only reason I can think of is sabotage from the dealer that last serviced the car. So the sand must have been inside the mower but, How it got there? Yesterday I did a quick inspection and the dipstick and dipstick tube seals are OK. Are there any other ways into the crankcase???, Maybe one day I was careless and somehow dirt got inside the engine, if that is the case then my OCD really has let me down!!! Is there anyone out there that had the same experience of sand or dirt inside a mower?? And what should I do now??? Change the oil again in the mower or let it run another 6 months???