I'll leave out the sarcasm in this post. Driving on a freeway is situational. When cruising at the speed limit on a flat highway, I wish I had a 7th gear. I have come up to people who were going 60 mph and there was no other traffic so I left the car in 6th and easily passed them. However, there is minimal torque available when driving at 60 mph in 6th gear. In my part of the state, people often drive 75 mph on the highways; sometimes many are cruising at 80 mph. (Not legal, but a real situation that can't be ignored.) To move into a fast line of traffic to pass a car requires some oomph to make a clean pass. That type of pass is achieved by downshifting to a lower gear. When commuting on an expressway, I often found myself driving between 3K and 4K rpm so I would have better response from the go pedal as traffic ebbed and flowed.
Referring to the manual's shift points is just a point of reference that applies when there is no load on the engine and no urgency for forward motion. I doubt people trying to match traffic speed when entering a freeway will shift into 6th gear at 52 mph.
5th or 6th gear? 5th if pulling on an incline. If you have reached your desired cruising speed, 6th gear makes more sense. Gas mileage? I let gas gas mileage find it's own level; I drive to the situation.

 

Many of us are still incredulous the original posting was made. Hope we didn't frighten him away. We were all new once.

-- Chuck

 

Hell, I'm in 6th by 40 mph in town. It's not like I would need to accelerate quickly and if I did have to I can grab 3rd gear. But out on any hwy. I'm in 6th.

Rod