With EngineCheckUp test, a single drop of warm oil from the dipstick can help diagnose contaminants before they cause serious engine damage. This one-step diagnostic kit requires no tools and can be used anywhere. Because oil is in constant contact with engine components, it absorbs byproducts of the combustion process. Applying one drop of warm oil to the kit's test medium allows the detection of carbon, water, antifreeze, fuel and other damaging sediments. The oil spreads into four concentric circles on the test medium and changes shape and color depending on the contaminants detected.