Ricciardo ended FP2 fifth fastest, and was just 0.390s off Lewis Hamilton's record lap time around the Austrian circuit.
An FIA document, issued on Friday evening, confirmed that the gearbox inside Hamilton's W08 has been changed ahead of this weekend's race at the Red Bull Ring. Lewis was quickest this morning with the soft, so obviously they have a quick vehicle but still to be quickest on that tire shows it is pretty durable and strong around here.
"We had to swap out a spark plug during FP2 (the second session), but the guys did a great job to turn the vehicle around and we still managed to complete our programme", Hamilton said. This track punishes you if you make a mistake.
Red Bull was in the mix at the front on Friday as well, with Max Verstappen splitting Hamilton and Bottas in first practice then taking fourth in the afternoon.
Fernando Alonso was eighth best in P2 on an encouraging day for the struggling McLaren team. However, the Spanish driver was also one of several to spin on turn six, and again on turn seven and into the gravel. Verstappen, Haas driver Romain Grosjean, and Toro Rosso's Carlos Sainz Jr wobbled on the same turn - as did Hamilton late into P1.
Bottas, who has reiterated his Formula 1 world title charge having closed the deficit to 42 points on Vettel thanks to his back-to-back second places, is exclusively focusing on pole position in Austria as he looks to take on Vettel and Hamilton who have largely dominated the sharp end in 2017.
Despite that run he still trails Ferrari's Sebastian Vettel - with whom he clashed behind the safety auto in Azerbaijan last race - by 14 points in the championship.