In the '80s GM, IIRC, said quit using a 30 weight spread and go to a lower number. I changed from 10W-40 to 10W-30 in my Chevy and my oil consumption dropped to near zero. Now days there is more than a 30 point spread in many oils. Using a modern synthetic oil does the 30 or more spread make any difference? I'm talking about 0W-40 and 15W-50 oils foe example. TIA