Exactly. As long as there are no 'perceptible' problems, people assume its working. But just because you have no apparent issues doesnt mean it is working as it should nor is it the best for the application.
I mean I can put a 40 weight engine oil in the motor if I wanted. Will it work? Yeah and quite possibly for a long time. Is it the best thing that can go in? No. You may not see any 'perceptible' problems for quite some time but the added stress on the pumping system and such will take their toll.
