best choice for rearend lube?

best choice for rearend lube eh. I think you may be asking in the wrong forum

My buddy uses Lucas on his race car both in the rear-end and the oil,and he swears by it...I recently adopted his formula to my ride and i've noticed a solid difference with the way the engine does'nt sound like a sewingmachine...as far as the rear-end i really did'nt have any problems before hand,but as a preventative maitinance measure i put the lucas in.