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I recently changed the engine oil in my diesel car but the oil showing on the dipstick was still pretty much black soon after.

I was wondering if I should have used an engine flush.

I don't understand how they work actually, in that how do they de-gunk the engine without having some residual detrimental effect on the lubrication of the new oil ?


From the "Ask Jack" archives - 4 September 2009


It would depend on the condition of the engine in general. If the oil has not been changed for some time previously, then it may need to be replaced more frequently than recommended to 'clean' the engine up.

The trouble with engine flushes is they can start to dislodge deposits which can cause bigger problems later such as blocking oil pick-up strainers in the sump, if the engine is badly contaminated.

I suggest you get the engine hot and changed the oil again if you are worried about its colour. Or take the vehicle into the franchise dealer and ask them to have a look at the oil colour and ask them to recommend the correct grade of diesel oil for the car.