Hi. I was reading the post about NOACK by K9JADON but did not want to hijack his thread. NOACK number is an oils ability to withstand evaporation. Lower number the better. Is this correct? The vapours from the oil bung up the pcv system along with the intercooler and inlet manifold on a turbo diesel engine. Therefore will an oil with lower NOACK cause less problems? Are they separate issues? Incidentally I have an OM642 unit. Forgive me if they are dumb questions. Many thanks. Tikka.