In 1985 Bignotti went into retirement and the team was reorganized as Team Cotter with Guerrero driving their No. 9 Master Mechanic/True Value March 85C-Cosworth DFX. Compared to the previous season 1985 was a disappointment highlighted by a 3rd-place finish at the Indianapolis 500 and a 4th at the Stroh's 300K at Laguna Seca Raceway. The season also saw Guerrero retire out of a race twice while leading, first at the Michigan 500 at Michigan International Speedway (due to gearbox issues) and then at the Molson Indy 300 at Sanair Super Speedway (due to Guerrero crashing). Guerrero finished the season 17th in points with 34 points.