Is it true that, when changing from mineral to fully synthetic oil (mobile 1), there is a risk that combustion residues in the engine will dissolve uncontrollably, clog the oil sieve and cause engine damage, so that an engine that is about 100,000 km fuelled with mineral engine oil should no longer be switched to synthetic oil? Is it true that when switching to fully synthetic oil, there is a risk that the engine will be replaced with synthetic oil. I really don’t know myself at all and would like to switch my Saab to Mobile 1, but I don’t know what kind of oil was in it so far. Should the conversion really solve coal residues, wouldn’t that be really good, would it?