WEAVER: Is Toyota's dominance short-lived?

Toyota is on top of the NASCAR mountain right now – but its advantage isn't as perpetual as it appears.

With its third points-paying race victory in a row on Sunday night in the Coca-Cola 600, Toyota Racing Development has now won eight of 13 Sprint Cup events this season. Martin Truex Jr. was untouchable, leading all but eight laps and cementing Toyota as the manufacturer to beat entering the summer stretch.

Make no mistake: It was a colossal butt-whooping.

Truex was passed under green flag conditions just once – by Jimmie Johnson on a restart – and that only lasted half a lap. Johnson thought Truex was playing with the field, a belief the victor didn't refute.

"No, I had to give him something for being such a good sport," Truex said. "I just wanted to give him a taste of what it might feel like to lead this thing."

He was joking, but that's what Toyota is doing right now: ripping the field apart and picking up where Kyle Busch left off last season on his way to the Sprint Cup championship. But true to form in NASCAR, such stretches of dominance aren't meant to last.

It was hard to tell from looking at the box score, but the Chevrolets of Johnson and Kevin Harvick (left) were right there at the end but just couldn't make the move. Johnson called the car among the best he's ever had at Charlotte Motor Speedway, but it simply wasn't as powerful as the one Truex had under him.

Harvick has made the Championship 4 in both seasons since NASCAR first employed an elimination playoff format and is again leading the championship standings halfway through the regular season.

Johnson has two victories this year, and you should never count out the six-time champion.

Even Ford is showing signs of life, with Joey Logano joining Brad Keselowski in Victory Lane (albeit in the Sprint All-Star Race) and two-time Xfinity Series champion Ricky Stenhouse Jr. helping Roush Fenway Racing start to creep back toward the top 10.

The other manufacturers aren't the only potentially threats to Toyota's recent stretch of dominance. Some big changes might be coming to the Sprint Cup Series in terms of rule changes designed to improve competition and generate parity.

NASCAR will test a new competition package at the upcoming races in Michigan and Kentucky. Those changes consist of a reduction in spoiler height from 3.5 inches to 2.5 inches, a splitter reduction of two inches and a resizing of the rear deck fin to complement the spoiler change.

That's a pretty significant swing.

The changes are going to dramatically change the balance of these cars and potentially bring the field closer together. That was certainly the case last year, when NASCAR conducted a similar experiment at Kentucky and Darlington, which eventually gave birth to the current lower downforce configuration. NASCAR officials have said publicly that they don't expect the experimental package to be used again for the remainder of the season, but how could NASCAR not use it if the changes produce considerably better racing?

With that in mind, Toyota has several factors working against it, and Truex knows his rivals are nipping at his heels.

"It's still early in the year," Truex said. "There's a long way to go and everybody is going to be working hard trying to catch up to us, so we need to keep working hard to try to find a little bit more. ... Our downforce stuff has been excellent but we've been off a tick on the short tracks so we'll see what we can do to keep getting better."

As usual, there's no room for complacency in the NASCAR Sprint Cup Series.