The 33-year-old man was detained by police who had been using a speed gun on a bridge over the main A420 near Abingdon, on Saturday.
The man has been released on police bail until February 17.
Helphire, said an employee who had 'borrowed' a £98,000 Porsche 911 Turbo without permission had since resigned.
Police say the man reached 172mph in a £98,000 3.6-litre Porsche 911 Turbo on Saturday.
In 2003, car dealer Jason McAllister was caught doing 156mph in his BMW M3 3.2-litre in Scotland. He was jailed for five months.