For the T4 vs the T6? Totally up to the user. I, personally, use the T6 but I would guess that if you are having to change the oil pretty frequently, like in construction where you can put 100+ hours on a machine in a week or 2, the cheaper oil would be more desirable.
So do I and I have a few coated cardboard quarts with metal ends of Valvoline motor oil that you have to open with a church key on the shelf. I should sell them. One has a price tag on the top. 30 cents at Western Auto.I can remember when the good motor oils were around 39 cents a quart. Store and discount brands were around 19 cents a quart. The cost of an oil filter was always higher than the oil. Usually $2-$3.
I worked at my dad's gas station in high school. We had a few of those high-end push-in spouts. Sometimes you still needed to use a funnel. The church key was always a good standby. My uncle used to carry one of those in his pocket. But it wasn't for opening oil cans.
I also remember those cans and I had one of those metal push in spouts in my truck toolbox. I likewise remember going to full serve gas stations as a kid with my dad and the attendant always checked the oil. Frequently those 1960s era cars were “down a quart” and the attendant would add the oil along with refueling and washing the windshield.I worked at my dad's gas station in high school. We had a few of those high-end push-in spouts. Sometimes you still needed to use a funnel. The church key was always a good standby. My uncle used to carry one of those in his pocket. But it wasn't for opening oil cans.
Since they sell synthetic blend oils, I don’t think mixing is a problem.
Yeah, I've always wondered about that, whether there was something more to "blends" than just mixing the two. Not knowing, I've just always played it safe, and used one or the other, never the two mixed.