mk2 Posted August 15, 2025 Report Share Posted August 15, 2025 This has been bugging me for ages. I'm convinced the design is flawed, but if someone could tell me I'm wrong I'd be very grateful. Just changed the oil on an AMF engine today. Everytime I do one of these disposable cartridge filters I get scared. When you lift up the old filter, all the crap on the outside gets flushed into the clean oil circuit, which kind of defeats the point of changing the filter and keeping the engine clean. At least that's how I see it. The peg or bung with the little O ring blocks the drain back to the sump, forcing clean oil around the engine. The moment that is opened up, the entire contents of the oil filter housing BOTH cleaned and dirty side cross over the clean oil feed hole and into the sump. Lots of crap always falls into the clean circuit. It is impossible to stop it happening. Am I missing something? Pics: Quote Link to comment Share on other sites More sharing options...
ObjectiveAway Posted August 17, 2025 Report Share Posted August 17, 2025 Mk2 you are right, VW dont think there is something significantly bad if you get few drops in clean oil feed. By chance isnt clean oil feed always full? 1 Quote Link to comment Share on other sites More sharing options...
mk2 Posted August 17, 2025 Author Report Share Posted August 17, 2025 I always change oil on a hot engine- so by the time I stop, open the bonnet and unscrew the filter housing, the clean runny oil feed hole is already empty. The crazy thing is that the filter housing drain is at the centre of the clean feed- which means the dirty side, with all the heavier particles are always at the lowest edge, ready to pour straight into the clean feed gallery. This happens the moment you lift up the filter by uscrewing the housing. Why didn't they position the drain on the outside, so when you lift it, no contamination happens?! Then clean oil would flush any trapped dirt away... Quote Link to comment Share on other sites More sharing options...
ObjectiveAway Posted August 17, 2025 Report Share Posted August 17, 2025 Would it help if you suck out all the oil from the dipstick hole before removing the filter? 1 Quote Link to comment Share on other sites More sharing options...
mk2 Posted August 18, 2025 Author Report Share Posted August 18, 2025 Maybe that might work. When the engine is off, does the oil filter empty? On regular screw-on filters, there is that rubber one way gasket built into the base of the filter, which helps keep oil in the system. So when you start up, the oil is already there and just needs pressurising. At least that is how I understand it? Quote Link to comment Share on other sites More sharing options...
ObjectiveAway Posted August 18, 2025 Report Share Posted August 18, 2025 5 hours ago, mk2 said: Maybe that might work. I totally missed the point. That will not work, dipstick lays near oil drain pug. 5 hours ago, mk2 said: When the engine is off, does the oil filter empty? I think this explains why VW designed it this way – if the passage is already full and it can only be supplied by pressure then you can’t pour any oil into the clean oil feed. Also, since it is full, could there even be backflow from the clean oil feed? Quote Link to comment Share on other sites More sharing options...
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