Adding oil when foiling a brisket?

[Travis D]

I usually add some liquid when foiling a brisket, especially if it's only the flat. I've been making a marinade based on the recipe in Wicked Good Barbecue. Their recipe calls for a 1/4C of canola oil in addition to the usual flavor boosters (beer, beef stock, rub, ect) Is there a reason for adding oil to a liquid when foiling? I know the meat can't absorb the extra fat. There is always lots of rendered fat in the foil after the cook. Is it to lower the boiling point of the liquid? inquiring minds want to know.

 

[Jon Des.]

I suspect that its to emulsify the sauce (assuming you whisk it) and/or to help it stick.