I find the location of the gas station weird, like everyone else. I'm a little navigationally challenged and if people had to retrace my steps to try to find me, my routes would seem downright insane. But there are many gas stations in that area (from what I can see on google maps), so it would be easy to stop someplace else if you got turned around. It's also not rare for me to take little side roads and detours just to listen to music or get a few more minutes alone before the day starts. I don't think he would do this if he was expected home and had an early meeting.
<modsnip> since he seems to be an incredibly kind and thoughtful person, it seemed totally possible he stopped for treats to take home to his house guests. A lot of other people have mentioned this, as well. I see a donut shop that is very close to the area where others on this forum have said that he lives, and he could actually get to his house using only residential roads if he stopped there on his way home. I don't see anything better than that donut shop near the gas station.
Another thought ... In the gym video, he puts his bag behind the driver's seat. I assume his money was possibly in there, along with his ID and whatever else he'd take to the gym. In the gas station video, he doesn't carry his bag with him so it is probably still stashed behind the seat. If he did stop somewhere else and it was still dark, it would be easy to see him reach back, grab some cash, and put the bag back behind the seat. Eyes off of his surroundings for a minute, not to mention if someone saw him they would know his stuff was in the car if he left.
A final thought on the location of the gas station. An obvious (to me) thing you would be able to quickly do that early is pick up an rx. The gas station is close to medical centers, and even though most of us probably have our pharmacy closer to our house than our doctor's office, he doesn't live that far from the university hospitals and he may have his pharmacy over there. It would be cheap enough to pay with cash (maybe), so the only way to find out if he did pick up some meds is if he used a rewards card or something.