I really want the car. I'm confident that it will make a dependable ride. I'm concerned about it having been overheated. The owner told me that it did overheat. I'll get the head fixed if need be but I'd much rather just replace the gasket. I'm gonna see if the owner takes my offer. We'll see.

Explain more about the fuel preheater. How would black oil get into the coolant via the preheater?