I have heard that dark engine oil indicates the need for an oil change. Is this so?No! The way modern detergent motor oil works is that minute particles of soot are suspended in the oil. These minute particles pose no danger to your engine, but they cause the oil to darken. A non-detergent oil would stay clearer than a detergent oil because all the soot would be left on the internal engine parts and would create sludge.
If you never changed your oil, eventually the oil would no longer be able to suspend any more particles in the oil and sludge would form. Fortunately, by following the manufacturer's recommended oil change interval, you are changing your oil long before the oil has become saturated. Remember, a good oil should get dirty as it does it's work cleaning out the engine. The dispersant should stop all the gunk from depositing in the oil pan.
A good test to see if the oil needs changing is to feel it in your fingers.(Caution: used oil is toxic and carcinogenic. If you get it on your skin, it could cause problems. Use gloves!) If it feels grity, that is an indication it should be changed.
