It is hard to link those things that are happening to an oil change but anything is possible. However, it feels like some info is missing. How long after the oil change did this start? Was it doing as soon as you picked it up or some days after?
Next, did they only do an oil change or did they perform other services as well?
Based on the info so far, I don't see how it is related and I am not sure the heater core makes sense either if the speedometer isn't working and transmission issues. However, I suspect they aren't address that. More then likely the heater core will just address the coolant issue.
Let us know this info and we can go from there. Thanks
Thursday, July 8th, 2021 AT 10:28 AM