I am trying to purchase a few oil filter caps so that I can service my Prius and my friend's new Civic. Well, I was hoping to purchase one that can service both cars... My understanding is that the Toyota cartridge filter requires a 64mm cap, preferably metal. CTA tools states in their application chart that #2485, which is 64mm, is OK for the genuine Honda filter and the Toyota cartridge filter. However, Assenmacher recommends their 64mm cap (#TOY640) for the Toyota cartridge filter applications and their 63mm cap (#5063) for the Nissan and Honda applications. Someone on the prius forum said their genuine Honda filter cap also works fine for their Prius cartridge filter. In addition, the genuine Honda cap has a warning which states that it will not work on aftermarket equivalent filters. This makes sense, because CTA Tools' page is saying that the Fram equivalent filter for Hondas needs a 65mm socket and not a 64? Plain weird, as I guess this means the OE Honda filter has a slightly smaller end. I measured the Pureone filter I have in-stock for our Nissan 3.5 and the filter measures 63mm so I think Assenmacher's recommendation of a 63mm filter cap for Nissans is spot-on. However, this may mean they are wrong about using a 63mm for Hondas? Unfortunately the Honda's filter location prohibits use of filter pliers. You could try, but I would rather not risk it (and face the humiliation) if I am wrong and I am unable to remove the ultra-tight factory filter on the first visit. Pandabear told me that some of his 64mm filter caps are too small for the Honda filters, go figure. So, for those of you who have a Honda, are you using a 63mm or 64mm filter cap? Or 65mm? I think I am going crazy here trying to sort this out. Perhaps I should just go out and buy three sockets-- the dealer Honda one, the Assenmacher 64mm for the Prius and some sort of universal for every other aftermarket Honda filter. Thanks.