Does anyone know what would cause oil in the coolant reservoir but not in the radiator?

 

If you have oil in your reservoir you have a blown head gasket my friend. You can see it better in the reservoir then you can in the radiator. Unless someone is pulling a prank on you . . . It's just simple mechanics to arrive at that conclusion.

 

The engine was already replaced 2 years ago. How can this be? Can it be a seal? Seems too new to die

 

Bad thermostats are the main problem .high heat bad gas. Engine could have 100 miles on it and blow a head gasket with bad thermostat

 

It overheated one time on the remanufactured engine, i shut it off, waited, turned it on, and it never overheated again. I'm going to freak out I just got a nice job...

 

When did you notice? Was it like you never looked and just saw it, or you looked recently and saw it green and now few days later its dark like oil in it? Might be just dirty, not oil IMO.

 

Bought car at 116k never changed my thermostat in 85k....never had A problem now I'm at 205K....I did change the Antifreeze twice tho.

 

these engines warp very easily, that is your problem. one overheat will warp heads.

Thermostats shouldn't be replaced like tires ,you just have to watch the coolant temp gauge . And if it starts rising shut the car off.

 

Yeah. Looks like a head gasket. Good news is that it seems to me minor since the car still seems to be running alright.

I've seen this stuff work in person several times on worse leaks than yours.
It's definitely worth a try. You've got nothing to loose other than the purchase cost.
You don't have to get it here but get this exact one.
https://www.walmart.com/ip/BlueDevil...&wl13=&veh=sem