I've had good luck with hylomar, its all we used at Michigan Kenworth. We never used a drop of RTV unless we didnt have any hylomar in the correct temp range. Just be careful about which you get, we had over 15 different bins of the stuff, each with a different purpose.
It worked great on the heavy duty diesels, and its all I use on my truck instead of RTV or other types of gasket maker. To give our range of uses back when I was working for Kenworth, we used it for everything from exhaust sealant to engine sealing to windshield urethane. We used so much of their stuff they would ship it to us and our sister branch directly on semi-trailers
I recommend their products.