Honda's engine boss Yusuke Hasegawa admits to be troubled by the power unit issues which hit McLaren early on in the first week of testing.
The Woking-based outfit had only limited running on Monday and Tuesday. While the oil tank issue was quickly indentified and fixed, Honda has yet to determine the reason its second engine failed.
"The first day we had an oil system issue, the oil tank," Hasegawa told Spanish broadcaster Movistar.
" 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 had 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."
Honda is bringing an upgraded engine to Barcelona next week, a spec it intends to race in Melbourne.
But on the back of this week's woes, speculation is rife that only limited horse power shall be unleashed in order to protect reliability, with an output even below the power of its 2016 engine!
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