Mansell, the first reigning Formula One world champion to switch from grand prix racing to Indycars, unofficially cut the previous best for the 1.77km Firebird East track by 0.8 of a second.
'I am delighted not only to go so quickly but also to make such a good start with my new team,' he said. 'This week is really a learning week for me and I feel we have achieved a great deal already.
'The Lola-Ford car has a terrific engine and it is up to me to improve myself and to learn all about racing on ovals later in the week.'
Mansell was driving a 1992- specification car on the flat and normally regulated road circuit, but tomorrow he will drive for the first time on a concrete-walled, banked oval at the Phoenix International Speedway. He will also be driving the 1993 specification Lola-Ford for the first time.
A large press corps watched Mansell in action. 'This is the biggest media event at a test session in the 81 years of IndyCar racing,' a team spokesman said.