The 28-year-old clocked 14.51 seconds, just 0.16sec slower than the mark set by Bolt at the same event in 2009, and on a typically rainy Sunday in Manchester that made conditions far from ideal for sprinting.
"I'm satisfied with my time. I think it's pretty fast, but I've just got to stay healthy and be ready," Gay told the BBC afterwards.
Gay has been plagued by injuries since winning the 100m and 200m world titles in Osaka in 2007.
He missed out on the Olympic final in Beijing the following year and pulled out of the 200m after taking 100m silver at the World Championships in Berlin two years ago.
"I've missed a lot of training this year because of a couple of little niggles and injuries so I'm pretty impressed with my performance," added Gay, after clocking 8.8sec for the 100m stretch between 50m and the finish.
"I'm feeling OK. I'm a little bit sore, but nothing major. I'm feeling pretty good. I came through the first 100m in 9.91, that's kind of where everyone else is in the world right now so that's not bad."
Meanwhile, Ethiopia distance great Haile Gebrselassie said British runner-up Chris Thompson was one to watch after winning the Manchester 10 kilometre race that took place earlier in the day.
Gebrselassie, who won in a time of 28 minutes and 10 seconds, only pulled away from Thompson in the closing two kilometres.
"I didn't expect that from Chris Thompson," said the 38-year-old Gebrselassie, unbeaten in 10km road races going back to 1994.
"Others yes, but this boy is amazing, amazing, he's really super.
"In the future he'll be the one. I tested him, I listened to his breathing when he was behind me.
"I was surprised. If I brought him until the last kick, (there would have been) no chance for me. He's a really wonderful athlete. I just thought he'd be like another European athlete, but he's not like that, he's tougher.
"This boy is the one to watch."
The 30-year-old Thompson, the 10,000m silver medallist at last year's European Championships, added: "I was thinking with just over a mile and a half to go that it was coming to crunch time.
"It was going exactly as I imagined it up until that point, I just needed to see if I was strong enough and I just unfortunately wasn't.
"I could sense when I was next to him I had him a little bit worried and that was a nice feeling... I really want to race him again next year, I want another crack."