Hybrid combinations of graphene nanoplatelets and phosphonium ionic liquids as lubricant additives for a polyalphaolefin

•Three phosphonium ILs separately combined with graphene nanoplatelets as hybrid additives in PAO 32 were investigated.•Hybrid additives improve the tribological performance of PAO 32 and of single additives.•0.05 wt% GnPs and 1 wt% IL addition to PAO32 led to friction and wear reductions up to 36% and 27%, respectively.•Hybrid lubricants containing [P6,6,6,14]+ led to the best combined capabilities.•Raman microscopy revealed protective tribofilms on the wear tracks composed by ILs and/or GnPs.