HI: 1992 Volvo 240 Aisin Warner AW 70? 4 w/od. Should have small drain plug in bottom. Probably over225k miles, perhaps never changed. Need to change soon. Thinking quickest way is just drain and fill, change filter, flush, etc. in spring? Thoughts? Also wondering if magnetic plug exists? Looks short, few threads,haven't found specs yet. Planning Valvoline synthetic HM Dexron III? WM $18? 1 gallon. Thanks.