better then diesel

At $25 a gallon the Repsol 4T 10w-40 oil cost more then Shell's Rotella T 15w-50 diesel oil ($20 a gallon) I usually run and $.50 more then the cheapest oil at the motorcycle shop.

I've never known oil to make much of a difference. Shell Rotella T 15w-50 diesel oil kept the top end of my Suzuki SV 650 looking good up until its 80,000 mile. At the other end of the spectrum, running full synthetic 5w-40 oil at $20 per quart made no noticeable performance difference either. Whether it was Repsol's racing heritage or idle curiosity, I purchased the premium brand for an extra $5.50 with sales tax.

Whether the oil makes any difference or no is negligible but I was impressed with the tube that is included with the Repsol oil. Nice touch, especially if you don't have a funnel handy.