The Ilmor Mercedes V - 8 engine , also a mainstay CART powerplant , was permitted .
The only time engine was used was a one - off at the 1996 Indy 500 by Galles Racing .
The Ilmor Mercedes V - 8 engine , also a mainstay CART powerplant , was permitted , but the only time it was used was a one - off at the 1996 Indy 500 by Galles Racing .