I had a 1993 Impreza with a 1.8 liter motor. It made it to 226,000 miles without head gasket failure. I had a 1998 Outback. The 2.5 liter motor in the 1998 was known to blow head gaskets at around 100k miles. The 1.8 and 2.2 liter motors had a better head gasket design, according to people I've talked to.