I’m not sure when that was last done. I can’t find the repair ticket, but it seems like it was about 5 years ago, and very likely over 100,000 miles. I can’t afford the $1000 to have it done again and that’s why I’m asking all these questions in case its something I’m going to have to do myself. The thermostat I installed a couple years ago is OEM. The radiator cap is also, but its not new. When I replaced the radiator, I bought a used OEM one from a junk yard and am using that cap that was with it.