Wind resistance is HUGE.
The faster you go the higher the resistance.
Slower is lower resistance.
I typically go 65 MPH on US interstate hwy with speed limits of 65 or 70 MPH.
Since traffic usually travels slightly over the speed limit this allows me
to travel in the right lane with cruise control on and not have to do
much lane or speed changing.
I see you are Canadian so you'll have to do the metric conversion.
Wind resistance increase is a CUBE of increase in speed.
This is from Drag (physics) - Wikipedia, the free encyclopedia
A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). With a doubling of speed the drag (force) quadruples per the formula.
So go as slow as traffic and your schedule will allow in order to get the