Murray produced a flawless performance in Arthur Ashe Stadium and Dimitrov was simply unable to cope as the Scot strolled to a 6-1 6-2 6-2 victory.
The British number one has now reached the last eight in 22 out of his last 23 grand slams and he will face Japan’s sixth seed Kei Nishikori for a place in the semi-finals.
The Scot also broke his own record serve speed delivering the ball to his opponent at 141mph.
He said: “I think that was lucky. I only did it once. So I’m not expecting to do it again.”
“I didn’t give him an opportunity, once I was ahead, to let him back in the match,” the No. 2-seeded Murray said.
“I served a bunch in the low 130s, mid-130s, which was good. I got a lot of free points with my serve tonight,” Murray said. “The conditions do a lot for you to serve quick. The balls are fast. I wanted to use that to my advantage as the tournament goes on. I did go up in (racket string) tension a little bit from the last match. Maybe that allowed me to feel like I was able to swing a little bit harder.”
Murray has lost three times in 10 meetings against Dimitrov.
Murray has a chance to become only the fourth man in the Open era to reach all four Grand Slam finals in a single season.
He lost to No. 1 Novak Djokovic in the finals of the Australian Open in January and French Open in June, before winning Wimbledon for the second time in July.
Since the professional era started in 1968, only Djokovic (2015), Roger Federer (2004, 2006 and 2007) and Rod Laver (1969, when he completed a calendar-year Grand Slam) have been to a season’s four major title matches.