what does this mean?

[Busted Knuckles]

Th head gaskets on a Supra engine will not last forever. The block is iron, and the head in aluminum. These expand at different rates, so the gasket gets a work out every time the car warms up and cools down. The same for even the normally bulletproof 22-R series. I owned a 22-r in a Hi-lux, and the head gasket lasted 225,000 miles. My dad owned the Supra from new, and gave it to me a souple of years ago with a BHG at 205,000 miles.