Nico Muller set the pace on a wet second day of Formula Renault 3.5 testing at Barcelona.
The Draco driver set a best of 1m48.116s early in the morning session and the tricky conditions that his benchmark time would not be bettered later in the day.
He said: “The new treads are at their best when there's a lot of water on the track. They offer an amazing amount of grip in extreme conditions.
“We need to learn how to look after these tyres, though, because they get worn really quickly if you're not careful and then you're in whole lot of trouble.
“We've still got a lot of work to do in the dry, but having the chance to work on a wet track has given us some useful preparation for the season ahead.”
Kevin Magnussen, quickest on the opening day in Barcelona, was second fastest and less than two tenths of a second behind Muller.
Marco Sorensen, Andre Negrao and Robin Frijns completed the top five.
Richie Stanaway was fastest in the afternoon session but conditions ensured he would not match Muller's leading time and was almost two seconds slower.
Pos Driver Team Time 1. Nico Muller International Draco Racing 1m48.116s 2. Kevin Magnussen Carlin 1m48.246s + 0.130 3. Marco Sorensen Lotus 1m48.337s + 0.221 4. Andre Negrao International Draco Racing 1m48.613s + 0.497 5. Robin Frijns Fortec Motorsports 1m49.186s + 1.070 6. Vittorio Ghirelli Comtec Racing 1m49.222s + 1.106 7. Richie Stanaway Lotus 1m49.280s + 1.164 8. Jake Rosenzweig Isr 1m49.388s + 1.272 9. Sam Bird Isr 1m49.411s + 1.295 10. Alexander Rossi Arden Caterham 1m49.530s + 1.414 11. Giovanni Venturini Bvm Target 1m49.552s + 1.436 12. Nick Yelloly Comtec Racing 1m49.589s + 1.473 13. Jules Bianchi Tech 1 Racing 1m49.720s + 1.604 14. Nicolay Martsenko Bvm Target 1m49.835s + 1.719 15. Kevin Korjus Tech 1 Racing 1m50.024s + 1.908 16. Carlos Huertas Fortec Motorsports 1m50.077s + 1.961 17. Arthur Pic Dams 1m50.130s + 2.014 18. Will Stevens Carlin 1m50.158s + 2.042 19. Mikhail Aleshin Team Rfr 1m50.185s + 2.069 20. Daniil Move P1 Motorsport 1m50.666s + 2.550 21. Lewis Williamson Arden Caterham 1m50.900s + 2.784 22. Anton Nebylitskiy Team Rfr 1m50.943s + 2.827 23. Walter GrubmÃ¼ller P1 Motorsport 1m50.953s + 2.837 24. Zoel Amberg Pons Racing 1m51.117s + 3.001 25. Lucas Foresti Dams 1m51.122s + 3.006 26. Yann Cunha Pons Racing 1m52.296s + 4.180