...The common user who's refueling isn't doing science.
I would say that person is applying practical knowledge.
Agreed. I said as much myself, twice.
(Which is why I'd suggested, quite literally and not as a put-down, that you may not have understood me, because your responses do not seem to show that you've understood that that's exactly what I told you myself, more than once.)
Be that as it may: okay, this much we do agree on.
However, the research team of an automobile company studying the fuel consumption of a new model is doing science.
Agreed. Except, it could just as well be you or me, it doesn't necessarily have to be some "research team", not unless you circularly define anyone who's "doing science" as a research team.
The question is what makes the research team doing science and not the common user.
Using the scientific method would be what makes something "doing science". This seems straightforward enough.
Part of the answer is that the research team controls the relevant variables and the common user does not.
Do you agree?
Sure. That control is part of the scientific method.
Do you think there are other relevant differences between science and non-science?
Obviously. All the other elements of the scientific method. Again, this is perfectly straightforward, at least in principle.
NOTE: this practical problem reflects one of the most important of the philosophy of science: that of the demarcation of science.
What you've suggested thus far, seems to be that using the scientific method would amount to doing science, and not following it, not. Nothing particularly profound there.
If all this "demarcation" means is simply a restatement of what the scientific method is, then I think we can take it that you, me, and everyone reading this, is familiar with it. No need to go into it, if that's all there is to it.
But if there's more to this demarcation, as you call it, than this circular re-definition of what the scientific method is, then sure, I'm interested. Rather than you or me googling out links, perhaps you could, if you're familiar with this, outline it briefly here, what it's about?