I did my heater core recently. Bought it at NAPA, even though I read a lot of posts suggesting that we buy an OEM heater core because the after market parts don't have as many radiator fins and don't provide as much heat. Well, now being in Alaska and fighting against very cold temperatures, I can verify that the advice is likely good. After doing the 6-8 hour job, my heat is not very hot. It is warm, but not even close to hot as it used to be when it was leaking, but of the OEM variety.