Ok guys I'm buying the gear diff this week! Now I'm on asphalt mostly but I plan on racing the car on carpet too this year....what oil should I get for the diff? I'm not sure which to get and will it make a big difference on which weight to get for the oil? Or do I need to pick one and just deal with it. I'm probably not racing carpet much compared to running it outside but would like it to handle the carpet when I go