Brampton to Oshawa is an hour...not 3 1/2 hours. I grew up in Scarborough, and can get there in 40 min from Brampton, and Oshawa is another 20 min max on the 401. (And I drive at the speed limit! No speeding for me!)
Unless you are taking a bus/train..then it's a lot longer.
wish I could help, but I don't have access to a car!