My son raced motocross from the age of 8-18. I was his self learned mechanic. He had a chain lube sponsor that supplied us with chain lube for free as long as he had their stickers on his bike. I used wd40 and gave the expensive chain lube that attracted more dirt than glue to people at the track. He never had a chain failure and never wore out a chain or sprockets faster then anyone else. I did however apply wd40 before every practice or moto. Wd40 cleans and lubes as long as you apply it often. Regular chain lube works well too, as long as you wipe off the dirt and reapply when needed.