I use a non contact infra or infa red thermomer, handy little gagdet on heavy equip repair and bikes to check temps. I carry it with me on most rides.
If you hear a miss on big engines, just check exhaust temps to isolate it to which cylinder, whole lot easier than the old ways, of pulling exhaust manifold to find the cold one.
Works on bikes, I checked temps before and after switching oils, interesting results. Considerably cooler engine and trans temps.