Toro Rosso focused on mileage after problem

The team's new STR12 made its track debut at Misano last week, but did not manage to complete the 100km of running permitted as it encountered an issue with the energy recovery system on the Renault unit.

The ERS is a second generation system introduced by Renault this year as part of a radical overhaul of its engine, which included an all-new architecture on the internal combustion engine.

The filming day was Toro Rosso's first run with Renault power since renewing its partnership with the French manufacturer, having run year-old Ferrari engines last year.

Asked if reliability was a concern after that problem, driver Carlos Sainz Jr replied: "I don't think we can be concerned from a filming day.

"During a filming day, you do pictures and filming and we managed to do all the pictures and all the filming, so we accomplished our objectives for that day.

"Hopefully [on Monday] we can have no issue and cover kilometres as this is the first week of testing.

"I will be looking more at the lap count than the lap time itself.

"This first week, we need to be patient and understand the new regs."

Toro Rosso technical chief James Key added the team's focus will be on reliability and F1's new-for-2017 bigger tyres during the first week of testing, with attention switching to performance at the second test.

Key refused to comment on the reliability problem at Misano but believes the engine is a "great leap forward".

"It was a sigh of relief really," said Key of the switch from a 2015-spec Ferrari engine to a current-spec Renault.

"Renault has done a great job.

"It's all relative - Mercedes seem very confident as well at the moment.

"They've done an outstanding job and seem to be confident, so we'll have to see where we are relative to them.

"It's difficult to tell with Honda and Ferrari at the moment, that picture I guess will emerge over the next couple of months, but for us it's a great leap forward.

"It's great working with Renault again actually - they're in good shape at the moment.

"We're looking forward to a developing engine. That's something we've missed the last two years."