Bautista, who has a strong chance of wrapping up his maiden WSBK title with a round to spare at the Indonesian venue, unseated his nearest championship rival Razgatlioglu at the top of the timesheets at the very end of the afternoon's second 45-minute session with a best time of 1m33.626s.
Reigning champion Razgatlioglu appeared to be the man to beat for most of the day on the freshly-resurfaced Mandalika track, topping the morning's opening 45-minute session with a best time of 1m36.938s.
As the track gripped up throughout the day, Razgatlioglu was able to lower the benchmark in the afternoon to a 1m34.088s, which stood as the best time until Bautista's chart-topping effort with a minute left on the clock.
The Ducati rider's time however was still more than a second off the 1m32.877s with which Razgatlioglu scored pole last year on WSBK's maiden visit to Mandalika, however.
Michael Ruben Rinaldi was third-fastest on the second of the works V4 Rs on a 1m34.590s, beating Kawasaki rider Jonathan Rea by a mere 0.005s.
Garrett Gerloff was an impressive fifth on his GRT Yamaha ahead of Barni Ducati man Xavi Fores, the second works Yamaha of Andrea Locatelli and the lead Honda of Xavi Vierge.
Honda's other factory rider, Iker Lecuona, was second-fastest in the morning session, within two tenths of Razgatlioglu's fastest time, and was in a similar position early in the afternoon until suffering a highside crash at Turn 4.
Lecuona was taken to the medical centre for checks following the incident, which briefly brought out the red flags.
Michael van der Mark was an encouraging fourth-fastest for BMW in the morning session, but the German manufacturer struggled to make an impression in the afternoon, with Scott Redding its best representative in 10th behind the Motocorsa Ducati of Axel Bassani.
Eugene Laverty also suffered a crash in the afternoon session at the same corner as Lecuona, but was able to walk away apparently uninjured.
Earlier in the session, MIE Honda's Hafizh Syahrin crashed at Turn 7 in another incident that brought out the red flags, with the Malaysian also being taken to the medical centre as a result.
World Superbike Mandalika - Practice 1 results:
| Cla | # | Rider | Bike | Time | Gap |
|---|---|---|---|---|---|
| 1 | 1 |  Toprak Razgatlioglu |
Yamaha | 1'36.938 | |
| 2 | 7 |  Iker Lecuona |
Honda | 1'37.127 | 0.189 |
| 3 | 19 | Alvaro Bautista |
Ducati | 1'37.509 | 0.571 |
| 4 | 60 |  Michael van der Mark |
BMW | 1'37.719 | 0.781 |
| 5 | 97 | Xavi Vierge |
Honda | 1'37.882 | 0.944 |
| 6 | 55 |  Andrea Locatelli |
Yamaha | 1'37.913 | 0.975 |
| 7 | 21 | Michael Ruben Rinaldi |
Ducati | 1'37.932 | 0.994 |
| 8 | 65 |  Jonathan Rea |
Kawasaki | 1'37.965 | 1.027 |
| 9 | 45 | Scott Redding |
BMW | 1'38.052 | 1.114 |
| 10 | 11 | Kyle Smith | Kawasaki | 1'38.114 | 1.176 |
| View full results | |||||
World Superbike Mandalika - Practice 2 results:
| Cla | # | Rider | Bike | Time | Gap |
|---|---|---|---|---|---|
| 1 | 19 |
Alvaro Bautista |
Ducati | 1'33.626 | |
| 2 | 1 |
Toprak Razgatlioglu |
Yamaha | 1'34.088 | 0.462 |
| 3 | 21 |
Michael Ruben Rinaldi |
Ducati | 1'34.590 | 0.964 |
| 4 | 65 |
Jonathan Rea |
Kawasaki | 1'34.595 | 0.969 |
| 5 | 31 |
 Garrett Gerloff |
Yamaha | 1'34.843 | 1.217 |
| 6 | 12 |
Xavi Fores |
Ducati | 1'34.871 | 1.245 |
| 7 | 55 |
Andrea Locatelli |
Yamaha | 1'34.941 | 1.315 |
| 8 | 97 |
Xavi Vierge |
Honda | 1'35.022 | 1.396 |
| 9 | 47 |
Axel Bassani |
Ducati | 1'35.139 | 1.513 |
| 10 | 45 |
Scott Redding |
BMW | 1'35.213 | 1.587 |
| View full results | |||||
