Automotive mobl1 15w50 is ok in primary and motor but in hot summer months it's better to use Mobil1 V Twin 20w50 in the motor to reduce the heat because it has heat reducing chemicals, in tranny use good quality Gear saver oil like Redline or Belray or whatever you prefer.

 

I began using SYN3 in all three applications, but figured there had to be compromises for one lubricant to serve three functions. I run Mobil 1 V-twin 20/50 in motor, HD's formula plus in primary, and going to switch from syn3 in trans to Redline shockproof trans lube due to the recommendations of others on this site.