Miguel Angel Morenatti/Associated Press
A lot of talk over the winter has been about the reliability issues teams will face with the new "powertrains"—that is, the engine, turbo, gearbox and ERS.
The switch from naturally aspirated V8s to turbocharged V6 hybrids is perhaps the biggest enforced technical change in F1 history.
The gearboxes now have eight forward gears, and will have to deal with substantially greater torque than their seven-speed predecessors.
The V6 engines have never been run in proper track conditions, and we haven't seen turbos in F1 since 1988. Plenty of failures of both are expected at Jerez.
And ERS (the dual-source successor to KERS) is new as well, delivering a 160-horsepower boost for around 33 seconds a lap. Losing it would be catastrophic to a driver's race—they won't be able to just live without it like they could if KERS failed.
The very newness of the components means failures are inevitable, but much will also come down to cooling. ERS and the turbo generate a lot more heat than the old engines did, and the teams have been forced to make educated guesses regarding keeping them at the correct temperature.
The teams won't be running flat-out in Jerez, but a realistic bad scenario would be five or six session-ending failures each day.
Definitely something to watch out for.