Royal Purple 75W140 Synthetic Gear Oil, 1 Quart

The oil is purple, but after a few miles of use will turn black. But it's not really a problem since I doubt your going to be glancing at your gear oil everyday. The oil it's self has so far served me we'll. Regular maintenance (Around 50,000 miles, with no mechanical design deficiencies shouldn't be a a stretch.) The oil it's self (like any good gear oil with anti-wear properties) smells just like rotten eggs (because of the ZDDP,a antiwear compound, which contains phosphorous) so be sure and use wear old clothes when you change the gear oil.