I've been running 20% used ATF, Motor Oil, and now free used ISO 32 hydraulic oil from work, two years. Same tank. I have a 10 micron Goldenrod plastic bowl filter on the 240D instead of the tiny primary filter, running metal 8mm tubes over to the filter mounted off the right front shock mount. These are available from farm supply stores, also Northern Tool Equipment mail order. I'm catching a lot of water in the bowl even when I don't run waste (dead of winter), and it is convenient to drain it out with the valve on the bottom of the plastic bowl, instead of spinning off a metal filter. I got disgusted with the tiny primary filter when my car stalled out 4 times on the way to and from Colorado, requiring filter change. Germany is a tiny country and people service their cars a lot there. Anybody have a ready source of 5 micron or less filter please post part number and auto supply, I know Wilkerson sells professional ones but the dealers don't like special orders under $100 and it is a long drive there and they are only open 8-4 M-F. I suspect the stock secondary filter is 5 micron, but of course I don't know. I carry a boat gasoline primer bulb and hose to prime the filter when I change it. It saved me a tow once when I got too much water in the filter, I was trying to burn of the "residue" of Reformulated gas left in the tank of my 59 ford after it sat for a year, the "gas" turned out to be mostly water with some kind of stinky RFG additive in it. It froze hard in December. RFG is why I bought the diesel, it won't run the '59 after it sits for 3 months or so.