They're usually optimistic in my experience. The R&T link doesn't work over here but Autocar - who do in-depth tests of cars - have tested all versions of the 718 and found the 0-60mph times were 5.4, 4.8 and 4.8 - for manual versions of the 718, 718S and 718GTS. The PDK will knock a couple of tenths off that but the base 718 is a long way from 4 seconds. One thing is that these cars were all relatively new, so they might get faster as they loosen up, but I suspect that the cars are mainly limited by how much power they can put down on the road through 2 lightly-loaded wheels. Even a Nissan GTR (with 560bhp, 470 lbft torque and 4WD) only manages 3.5 seconds.As for Porsche's own results: Never, never, ever trust measured metrics from a car manufacturer. C'mon: You know this. The number often has as much to do with marketing and make/model positioning than actual performance capability.