The calculated distance (air line) between Downsview-Roding-CFB and Oshawa is approximately 34 miles respectively 55 kilometers.
By car or train, the actual journey to Oshawa is certainly longer, as only the direct route (as the crow flies) between Downsview-Roding-CFB and Oshawa has been calculated here.
Air line (approximately)
55 kilometers
30 nautical miles