Same Deutz-Fahr had a neat engine oil test on its stand.
It’s something that’s come from the construction industry, where plant managers are pretty hot on oil quality. In fact many use sophisticated analysis equipment to ensure oils are changed before they lose their lubrication properties.
This test is simpler than that – you can pick up these oil test strips free from your local SDF dealer. Just put a blob of oil from the end of the dipstick on the circle, then compare it against the reference chart. Depending on which stain it matches most closely, you’ll get a green, yellow or red rating and can then take appropriate (and quite possibly urgent) action.