In 1988 Guerrero returned with Vince Granatelli Racing and originally drove the No. 2 STP/"" Lola T88/00-Cosworth DFX. At the season-opening Checker 200 at Phoenix International Raceway Guerrero qualified and finished in 2nd place. However, the remainder of the season was mostly a disappointment, such as the Indianapolis 500 where Guerrero qualified 12th and did not even make it out of second due to being collected by Scott Brayton. The team even attempted to use a year-old March 87C at select races to no avail. Guerrero's only top tens after Indianapolis were the Quaker State 500 at Pocono International Raceway in the Lola and the Bosch Spark Plugs Grand Prix at Nazareth Speedway in the March. After starting 10th at Long Beach Guerrero's best start was at Nazareth, where he started 11th. At the end of the season Guerrero finished 12th in points with 40 points, despite skipping two races.