Gayle punished a howler by Leeds goalkeeper Rob Green to putNewcastle ahead in the 23rd minute and netted the visitors' second early in the second half to take his tally for the campaign to 13 goals.
It was Newcastle's eighth straight win in the English second tier, keeping them on course for an immediate return to the Premier League.
"The performance of the team defending and attacking has been brilliant," Benitez told Sky Sports.
"It's good and all we have to do is keep doing the same thing, keep playing with the same intensity, no complacency.
"We know that until the end everything can happen, so we have to approach every game the same."
Benitez's men are five points clear of second-place Brighton and Hove Albion and nine points above third-place Reading.
Leeds remain a point outside the play-off places in seventh place.
"We gave them a goal, so obviously that against a good side makes it difficult," said Leeds manager Garry Monk.
"I'm happy with my team's effort. Obviously I'm disappointed with the result, but it doesn't change anything for us."
The meeting of two of England's fallen giants brought a crowd of 36,000 to Elland Road -- the first time Leeds had sold out a league game in almost six years.
Green produced an alert early block to deny Gayle from Jonjo Shelvey's quick free-kick, but midway through the first half the former England goalkeeper's blunder gifted Newcastle the lead.
Forced back onto his goal-line by Jack Colback's lofted ball, Green appeared caught in two minds and dropped the ball right in front of him, allowing the opportunistic Gayle to stab home.
Leeds responded positively, with Newcastle goalkeeper Karl Darlow saving smartly from Luke Ayling and Eunan O'Kane either side of half-time.
But Gayle doubled Newcastle's lead in the 54th minute, sliding in to touch home Vurnon Anita's low cross after a slick move down the visitors' right flank.
