My 2002 Malibu is leaking oil somehow into the coolant reservior. My mechanic is really puzzled by this. He’s heard of water getting into the oil.
Might this be transmission fluid rather than engine oil in the coolant? A leak in the oil cooler/radiator could cause this result.
The transmission cooler is built into the radiator. If it’s leaking, the transmission fluid will show up in the antifreeze. The transmission fluid won’t necessarily look red after traveling through the antifreeze.
If this is what has happened, antifreeze is likely also getting into the transmission, which is not good.
It’s also perfectly possible for engine oil to make its way into antifreeze via a bad head gasket.
You need a new mechanic too, apparently – anyone spinning wrenches professionally should know about these things already. Take the car somewhere else for a real diagnosis.
Yes you really need a new mechanic