Ya know, many years ago (late 80s or early 90s) when I lived in the USA, Roger visited me when traveling by train across the US and Canada. My now ex-wife and I met him for lunch and he looked at my 11B with a Frantz filter and I think he got an idea to do a full-flow filter. Yep, it dumps the filtered oil back to the sump but! The oil without a doubt is a lot cleaner than if there was no filter. I like clean oil. Clean oil is good. An external oil filter doesn’t not do nothing! Or something! 