Rea is 48 points clear of Englishman Sykes going into the final round at Qatar in a fortnight.
Fifty points are available and a 14th-paced finish would be enough for Rea.
Rea is attempting to become the first rider to seal successive World Superbike Championship successes since Carl Fogarty in 1999.
Sunday’s race followed a similar pattern to the opener 24 hours earlier in Spain.
Davies, who started third on the grid, hit the front on the first lap on his Ducati and was never threatened as he won by 5.8 seconds.
It was his ninth victory of the season but his good form has come too late to challenge for top spot.
The Kawasaki pair provided the drama in a battle for second place – Rea passed Sykes will 11 laps remaining and held on to pip him by 0.2 seconds.
Nicky Hayden made a late push for a podium place but he had to settle for fourth, ahead of Sylvain Guintoli and Michael van der Mark.
|World Superbike Championship 2016|
|1. Jonathan Rea (GB)||Kawasaki||462|
|2. Tom Sykes (GB)||Kawasaki||414|
|3. Chaz Davies (GB)||Ducati||395|
|4. Michael van der Mark (Ned)||Honda||255|
|5. Nicky Hayden (US)||Honda||228|
|6. Davide Giugliano (Ita)||Honda||197|