Cool! If you are flying along then suddenly see a big blob of black guck on you windshield, it's not a splatted bug, it's oil and you engine is about to go pffttt. Time to turn your nose towards home!!
I love that WOFF finds a way to let you know what is going on without having to resort to the onscreen messages (we've all used shift-D to turn that cheater message stuff turned off, right?
)