F1's governing body has addressed a clear reminder to all teams that burning engine oil as fuel is not allowed, following suspicions that Mercedes may have been using the scheme in qualifying last year.
The German manufacturer drew much interest by rival teams last season during its qualifying runs, appearing to enjoy the ability to turn up the power of its engine at will.
A suggestion put forward by rival teams was that Mercedes was cleverly burning additive-boosted oil to extract more performance from its V6 turbo hybrid unit as crucial moments of Q2 and Q3.
Current engine architecture technically enables the possibility of using oil as fuel, although this would represent a clear breach of F1's technical regulations as teams face strict limitations with regard to power-enhancing chemicals.
The issue was put on the table recently at meetings between technical figures, with Mercedes insisting it was not exploiting any illicit tactics.
Red Bull Racing sought clarification with the FIA however, which in turn prompted the governing to confirm to teams the stratagem's illegality.