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My oil and coolant mixed together, the dealership is recommending an engine flush among other things. Do I need one? A car repair centre says no. Your thoughts? – Claudette

Your question is sparse on the details as to how much coolant has migrated, but your engine oil and coolant should never be mixing.

Someone has made an error and put coolant where it wasn’t supposed to be, or an internal engine problem is occurring.

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An engine flush is absolutely necessary if it was human error. Alternatively, if coolant is leaking into the crankcase, you should have a repair centre look for the source immediately.

Besides being corrosive, coolant will dilute and contaminate the engine oil, limiting its ability to properly lubricate internal engine components. Prolonged driving with this condition will result in engine damage.

A couple of common sources: The engine’s intake manifold seals coolant passages and has coolant flowing through it. If the intake manifold cracks or the gasket fails, this will allow coolant to seep into the crankcase.

Another, albeit much more expensive repair is a failing head gasket which separates the upper and lower halves of the engine.

While they are both pricey repairs, not dealing with them will only lead to a much worse predicament.

Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail globedrive@globeandmail.com, placing “Lou’s Garage” in the subject line. Please note that we receive numerous queries and are unable to respond to all.

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