I get the impression that these engines wear out quickly

[1JB]

I don't know where you get the impression that most Porsche owners think their engines are "old" after 100M miles or what exactly you mean by "old." You seem to have made an assumption and validated it on your own to get a response to the simple question of how many people have done compression checks on their engines after 100M miles.

The engine in the Boxster has been basically the same as that in the 996 & 997 since it's introduction in 1996. That's when they went from air cooled to water cooled. There have been issues but I haven't heard an overall loss of compression at 100M miles as one of them. Given Porsche's history with the number of it's cars still on the road I am confident you will see many Boxsters, Caymans and Carrera's with the M96 engine with well over 100M miles on them happily motoring for many years to come.

As for the Audi 1.8T: "Consumer Reports has included the 1996-2001 Audi A4 1.8T on its list of used vehicles to avoid, principally because of a worse than average record with respect to engine repairs, but engine cooling, electrical and brake problems also caused concern." (form Canadian Driver) There also was a problem with sludge buildup in the oil that caused Audi to extend the warranty to 8 years. Not that I'm a big fan of Consumer Reports but I believe you will find the Boxster on their list and others of recommended cars to buy in its category.

The long and short of it is I think it's incorrect for you to assume that most think their Porsche engines are old at 100M miles. As with any car their may be issues but Porsche's track record upward of 100M miles certainly seems better than the most. I'd certainly take a Boxster with 100M miles on it over a 1999 Audi A4 1.8T with 100M miles on it if I were betting on reliability.