LOL. Good to see you wanting to get some real oil in there. I’d have zero hesitation using a HDEO such as Rotella 15W40 in your case. Sucks that Valvoline does not make VR1 in a 10W40 for you guys, however, mixing the 10W30 and 20W50 half and half would put you right there, ZERO issues with doing this, it’d make you a nice home brew 15W40!