My guess would be that the oil level didn't have much to do with your vibration problem... It's a quart and a half (or so, maybe a quart) before the low oil light comes on, and two quarts between the min and max levels on the dipstick. It will run fine when it's down a quart or two. I've heard the engine will even be okay with less oil than that, but DON'T take my word for it...
Incidentally, your thrumming problem sounds like a wheel balance issue. I had some significant vibration through my steering wheel for awhile, and a tire rotate + 4 wheel balance made it seriously better (though not entirely smooth).
Also, my low oil light is yellow. Are the Canada cars different?