Unfortunately, even when refined...the kind of oil from the oilsands, and much of our offshore production is 75% heavy crude. This isn't used for gasoline of diesel.
Our current refining abilities also only are able to refine 20% of our production. This is why we ship so much out.
So while the backyard garden analogy is nice, it's hardly indicative, or reflective of the actual situation.
"You have a backyard garden with highly sandy, iron rich soil, and you can only grow potatoes. In order to have a balanced diet, you need to take your potatoes to other markets, in order to trade for other fruits and vegetables"......is a more complete analogy.
Like it or not, we don't live in a protectionist economy. We participate in the world market, and as such, we pay world market prices for commodities in demand.