The problem is the VW Beetle is very small and under powered. Harry and Mouse are big. I would say an old Checker Marathon. Large, rugged, reliable and a very simple car..
The VW is a much simpler car. Air-cooled motor is a HUGE simplification, for example. Motor over rear axle = simpler transmission. etc etc etc.
Simple "reliability" isn't all of it.
We can make
reliable stuff that's still
complex... and it's that complexity that Harry hex'es!
(Also, I have a WAG that the Murphyonic Field is much stronger in the general direction the wizard is looking... so the motor &c
behind Harry could make a big difference, too.)