Sorry, I've only seen the T5 in 10w30 here locally. Didn't know it was available in 15w40. Shell does make a good quality oil, if I was to buy oil off the shelf the Rotella T6 would be my 1st choice. My cousin farms over 1000 acres and buys Rotella T in bulk and uses an oil analysis program to determine his OCI's. It holds up well for him.