The GM Ev-1 and the S10-E trucks used a very low viscosity oil in the reduction gear. It was a synthetic oil that (on the bottle) claimed "for electric vehicles, reduces viscous drag, increases vehicle range". The viscosity is about the same as water. Although I have never put it in my LEAF (its leased) I have put it in my I-MiEV which normally uses ATF in the reduction gear. When cold, there is a noticable (slight) difference in drag when coasting. The stuff worked and was designed for this purpose. It hasn't caused any problems with the I-MiEV and of course was used as OEM oil in all the GM EV's. The only problem is GM part # 12371288 is no longer available. I still have several pints that have the MDS data printed on the label but no clue as to who made the stuff for GM.