Oil in coolant expansion tank

Hi,

I have a really good warranty on my 2016 Grand Cherokee and an appointment on Tuesday. Had an oil change at a place I trust and they explained I have oil in my coolant overflow tank. They hinted it that Jeeps often have a seal st the oil cooler (if Cherokee even has one) and that I need a new gasket. They don't do that work so they are just notifying me.

A couple months ago I had the car at the dealer for a misfire (dealer discovered a plug wire, not sure of the name, was bad and replaced it) but being proactive tech noticed signs of oil pump starting to fail so they replaced pump for no additional charge.

Wondering about how oil gets in the coolant tank, any chance the oil change need or work got the coolant tank oily?

Dealer wants $211 to diagnose and if covered I'm back to my $100 warranty fee.

Any help or thoughts on what to do to be frugal?

 

Since the dealer performed some recent repairs to the oil pump there could be some correlation unless the oil change guy got distracted and dumped some oil down the wrong hole. If there is oil in the reservoir there will likely be oil in the radiator. I’d spend the money to let the dealer diagnose whether it was their work or a head gasket issue or someone dumped oil in the wrong port.