I have an oil temperature gauge which replaces the oil filler cap. It may not read the exact oil temperature, but gives a good indication of trends. I have a 20 miles commute, and even when it's warm running at 60mph on A roads for the most part the oil temperature is about 55 degrees C, until I have a slow mile or so when it starts to rise to 60 degrees C. The oil temp only gets to about 60 deg C if running above 30 mph in the UK. To get it higher then a few miles of town commuting is needed. A couple of hours on the motorway, assuming legal speeds won't be as effective, IMO, as 30 minutes of cross town riding, stop / start running.
I'd recommend cleaning out the oil filler cap of any gunge in there, and also checking that the crankcase breather isn't blocked. If they're OK and you're certain the oil level window is OK, then take it for a cross town ride.