its more important to check the oil for things like oil contamination and water contamination.
typically you'll know if its loosing oil or burning it from other evidence (wife complaining of black spots on drive way, inability to see out the back window or the engine revs jumping inexplicably followed by clouds of white smoke as the tacho hits the end peg but the engine sounds like its revving harder than a rotary)
how longs your engine going to last if the oil isnt oil any more but a 50/50 mix of diesel and oil or coolant and oil?

