With West Brom not playing until Sunday at Bristol City, United took full advantage to go six points ahead of their rivals.
An early Peter Lovenkrands strike and second-half goals from leading scorer Kevin Nolan and substitute Ryan Taylor made it a dozen goals for the Magpies in their last three home games.
United were forced into one change from the midweek success against Coventry City, with Alan Smith returning for the influential Wayne Routledge, who had picked up a calf injury.
The hosts got off to a dream start thanks in no small way to the positioning of Preston goalkeeper Andy Lonergan.
The approach work was both fluent and patient as Smith played in Lovenkrands. It was his left-sided cross that sailed over the head of the flat-footed shot-stopper and into the net.
That made it double figures for Lovenkrands, the third United player to achieve that feat this term but he was forced to limp off after just 15 minutes with a hamstring injury.
Seconds later Steve Harper came to United's rescue but knew little about it when Jon Parkin's close-range effort smashed the keeper fully in the face and flew to safety.
Andy Carroll set up Smith after 39 minutes and the skipper's drive from the edge of the box was clawed behind by Lonergan. From Danny Guthrie's corner Mike Williamson's header was turned onto the bar and sub Leon Best headed the rebound wide.
Preston's approach work was neat and tidy and came near to paying dividends in added time at the end of the first period when Parkin's first-time volley from the edge of the box flew just wide.
But it was United who doubled their tally after 55 minutes with Nolan's first goal in 11 matches. The leading scorer finished coolly when he was left one-on-one with Lonergan to notch his 12th of the campaign.
Ross Wallace almost pulled one back courtesy of a wicked deflection from his 30-yard free-kick. It had Harper scrambling but the ball crept safely behind for a corner.
And for the second time in three days, substitute Taylor finished with style in stoppage time to rubber-stamp another emphatic United win as he put away a cross from fellow replacement Fabrice Pancrate.