Renault says reigning Formula 1 world champion Sebastian Vettel will escape a grid penalty for the Belgian Grand Prix by reverting to the engine he used in Hungary.
Vettel sat out most of Friday practice at Spa because of an engine failure in FP1 on his Red Bull.
He completed just 11 laps before an ignition problem damaged his new unit, which Renault said was running in "similar" specification to the previous race.
Vettel has now fitted the maximum five permitted engines for the season and the German told reporters after Friday's sessions that he fears grid penalties will be inevitable over the course of the rest of the season.
But Renault's head of track operations, Remi Taffin, said Vettel would revert to an old unit to escape any sanction in Belgium.
"It was a fresh engine this morning, but he had an ignition problem," Taffin explained.
"Basically we lost power from one of the cylinders and it was traced to the ignition.
"Unfortunately we had to revert to an old engine, but this is OK because the spare one was used in Budapest.
"We haven't got the time to investigate too much so we go for the easy solution."
Taffin said Vettel's MGU-K was also damaged by overheating caused by the engine problem, which he also said was unrelated to Renault's "minor" summer developments.
Taffin said both components should be salvaged for future races.
"As a consequence [of the ignition problem] we had a broken exhaust, so you have a lot of overheating with the bodywork," Taffin added.
"You have to check quite a lot of looms and parts in the power unit to make sure it will work again. It should be OK for this engine to come back again next race."
This means Vettel should be able to delay taking a grid penalty for a further engine change until September's Italian GP at the earliest, but Taffin agreed a penalty was inevitable for Vettel before the end of the campaign.
"We can say from the next race onwards we could have the potential [for a penalty], but it could become a bit strategic so it's difficult to predict," Taffin said.
"[There is a] 99 per cent chance we will have a sixth one at some point."