The German, who could win the world championship in Japan this weekend, believes the scale of his team's advantage is nowhere near as big as his run of four consecutive victories, and a dominant performance in the Singapore Grand Prix, have suggested.
"I think there was probably one race that was pretty much an exception, and that was Singapore," said Vettel at Suzuka on Thursday.
"The gap we built up - it was two seconds quicker [per lap] than the cars behind - but that depended on who was behind us.
"In Korea, which is more similar to Spa, that gap was somewhere between three and six seconds for the whole race.
"With Schumacher, it was more like 30 seconds, which is a big difference.
"It is a nice cushion to have when you are three seconds down the road, but one stupid mistake in Korea with a lock up, which is very likely, then three seconds is nothing compared to 30."
Vettel insists that Red Bull has had to work extra hard since the summer break to bring the performance steps it has enjoyed, and he thinks the real breakthrough has been knocking Mercedes off the top spot in qualifying.
"We were always in a position to finish in strong positions on Sundays, but lately we have been strong in qualifying whereas at the beginning of the year Mercedes definitely seemed to have the upper hand," he said.
"There is no real explanation from our side, no one part that went on our car and all of a sudden it is that much quicker.
"We were able to improve the car, so arriving in Spa the car was better than it was since Hungary.
"I am sure the others do the same, but it seems we have lots of good parts coming lately.
"Also, there is the factor of understanding the car more than beginning of the season, and we can react quicker to change the set-up in the right manner."
Vettel needs to win the Japanese GP, with Fernando Alonso lower than eighth, to clinch his fourth successive world championship.