Mike Conway (LEFT) was quickest in morning practice ahead of qualifying for the IndyCar Series' Toronto round - despite crashing during the session.
Andretti Autosport driver Conway swapped the top spot with Dreyer & Reinbold's Justin Wilson early on, before setting the 1m00.047s lap that would stand as the best of the hour.
He also caused a full course yellow by sliding into the Turn 8 barriers, but was able to rejoin after repairs and set a similar pace.
Scott Dixon ended up being Conway's closest rival with a time 0.0584 seconds adrift in the top Ganassi car.
Helio Castroneves was the leading Penske driver in third, ahead of KV's Tony Kanaan and Wilson, with Ryan Hunter-Reay (Andretti) filling the top six.
Friday pacesetter Will Power was only 13th for Penske, behind top Canadians Alex Tagliani (Sam Schmidt) and James Hinchcliffe (Newman/Haas).