The Japanese manufacturer had a tough time at Barcelona this week, suffering an issue with its oil tank design on the first day but then, more seriously, having a failure on day two.

To further compound its problems, the engine did not appear to have delivered the performance step hoped for - and there were even suggestions that, for reliability reasons, it was having to run in a state that delivered less power than it had in 2016.

Honda's F1 engine chief Yusuke Hasegawa insists that the oil tank redesign will not be a big job, but the fact it did not know what went wrong on day two was a proper concern.

Speaking to Spanish TV station Movistar, Hasegawa said: "The first day we had an oil system issue, the oil tank. Normally the oil tank has to manage the oil level but this year we had some bad oil management so that is why we need to modify the oil tank system.

"The second day we have a mechanical issue and still we don't know the root cause of the problem. This is more fundamental and more serious I think. We need to find out what was causing the issue."

When asked if the problems could compromise Honda's start to the F1 season, Hasegawa said: "Oil tank definitely not. [The] mechanical issue, I don't know, yet to be confident about that, but of course I worry about that."

Latest spec

Honda is due to introduce its Melbourne-specification engine at the second Barcelona test next week, but its plan could be impacted by the results of the investigation into the failure.

The faulty power unit was removed from the car on Tuesday and flown immediately back to Japan where thorough analysis is taking place. There has not yet been an answer about what caused it to stop.

Should the work reveal a flaw in the engine design, then that could impact on what Honda brings to the opening races.

Asked if the new engine that will run next week will be Melbourne-spec, Hasegawa said: "Yes. It is supposed to, but we had a mechanical issue [so] currently I am discussing with Sakura members and Japanese members about next week's engine."

Strained relations

With high hopes that Honda would make big inroads to Mercedes this season, the troubled start to testing has been a blow to McLaren, and in particular Fernando Alonso.

While publicly both sides are keeping a brave face on matters, relations between Honda and McLaren behind the scenes are believed to be tense.

Hasegawa even hinted himself about the need for McLaren and Honda to 'argue' in such a situation they have found themselves in.

"In the tests, of course, this is a stage we need to overcome a lot of trouble," he explained. "So sometimes we need to argue or we need to have constructive discussion, but I think we are doing a very good job and we have a very good relationship."