I'm not a big fan of using diesel in gas engine. Even Shell does not recommend it.
No reason to use a 15/40 in most vehicles either.
I had a Ford van with a 351 gasser . Bought it with 105k... Sold it with 485k. Tried Citgo 10w-30...used too much and the oil temp soared. Went to Mobil1 10w-30 after the first change.
I have 30w CenPeCo for my race motor. I use a single grade for the alky motor.
