Hylomar sealant
I think the best thing about Hylomar is that it is non-hardening, defiantly my favourite. I'm not a fan of RTV because I have seen it gooped on and beads and strings of squeeze out, internally drop down and clog the oil pickup. That said I have used the right stuff sparingly on a lot on Japanese bikes and all sorts of cars because that is what is specified and never had a problem but I'm a nut on clean parts that are straight. I can certainly see the merit in the groove though.