When I do my oci this winter,I may use a 40 weight. Whats the main difference between yellow bottle 10W40 and 15W40 Gold? Just the fact that it`s an HDEO and maybe the 15W? I plan on staying with a Pennzoil dino.
The 15W-40 Gold has an HT/HS comparable to a 20W-50, while as the 10W-40 is not much thicker than a 10W-30.
The 15W-40 will be a better oil unless you get into freezing weather, which in South Texas is not uncommon.
I'd personally run a good 15W-40 HDEO in that engine year round.