INDIANAPOLIS – The first Indianapolis 500 for Dale Earnhardt Jr. will create indelible and vivid memories for a racing lifer who will enjoy an unusually fresh perspective in a long career.

Earnhardt will lead the field to the green flag in a Corvette pace car, hop onto the NBC broadcast for some high-profile commentary and probably duck into the Snake Pit to watch 30,000 grooving to an EDM song or two.

But what will he remember most about the 103rd running of the Indianapolis 500?

The emotion and energy that will be coursing through Indianapolis Motor Speedway moments before all of that begins.

“The big takeaway from events like the Kentucky Derby or the Indy 500 is just the energy and it’s not a tangible thing,” Earnhardt recently told NBCSports.com. ” It’s a feeling that you get when the event is about to happen. When you’re walking with the horses to the gate or pushing the cars out onto pit road. And there’s a lot of emotion in that and a feeling that’s amazing and incredible that you can’t describe. That’s probably going to be the coolest part.

“I’m absolutely sure that the feeling I have standing on that grid before the race begins will be unlike anything I’ve ever experienced at a NASCAR race, much less at a Super Bowl, or the Winter Olympics. All these things I’ve experienced over at NBC over the last several months, I think this will be the highlight.”

The 103rd Indianapolis 500, Sunday 11 a.m. on NBC: How to watch

Look for no greater validation of the Indianapolis 500’s standing as auto racing’s marquee event than the endorsement of a retired driver whose surname is synonymous with NASCAR.

But it’s also confirmation that a new era of once unimaginable détente is under way between America’s two biggest racing series – offering the promise of newfound collaboration between two longtime rivals.

The olive branches are sprouting everywhere.

A seven-time NASCAR Cup champion jets to IMS just for a gander at cars whizzing around at speeds roughly 40 mph faster than he’d ever seen at the 2.5-mile oval … the defending Indianapolis 500 champion makes a cameo on Earnhardt’s popular podcast … series executives check out and talk up the competition amid louder rumblings of sharing a race weekend stage at the same track.

IndyCar and NASCAR seem to be together at last as unlikely, but increasingly necessary allies in a motorsports landscape facing constant scrutiny from corporate sponsors seeking greater returns and discriminating fans eager for more entertainment.

“For a motorsports perspective, this is good for all of us,” said IndyCar president Jay Frye, whose background in NASCAR as a team executive makes him a “great friend” to many of his stock-car counterparts such as Mike Helton, Steve Phelps and Steve O’Donnell. “This is an industry. This is something that I think that the more we can do collectively to enhance the industry from a holistic perspective is great.

“So we’re talking about doing more down the road with our biggest events. I think the more we can do together, the better.”

That includes growing support for an IndyCar-NASCAR doubleheader, which was recently floated on (where else?) the Dale Jr. Download Podcast by NASCAR president Phelps, who traveled Friday to Indy and attended Carb Day with O’Donnell.

It’s been a welcome thaw in what once was one of racing’s biggest cold wars.

“I think we have to get away from, and I think more people are coming to that realization today in motorsports, that I don’t think we can be one against the other,” said Chip Ganassi, who has teams in IndyCar, NASCAR and IMSA. “We shouldn’t be in a circular firing squad. I don’t know what purpose that serves.”

The reaction to Earnhardt being named the pace car was a series of effusively welcoming social media posts, namely by reigning Brickyard champion Will Power (another recent Dale Jr. Download guest) and five-time series champion Scott Dixon, who was flummoxed as to why he was consulted on before final approval was given to bring in a 15-time NASCAR Most Popular Driver to drive an IndyCar pace car (Earnhardt was a last-minute fill-in choice).

“I think some people were a little worried about it, maybe just like it’s this NASCAR guy and all that,” Dixon told NBCSports.com with a chuckle. “And I was like, ‘This is awesome, man!’ And to come to his first Indy 500 and be part of the broadcast and also drive the pace car. It’s going to be his views of this spectacle for the first time in the broadcast. It’s massive.

“I think all around it’s a knockout great idea.”

Said Power, who invited Earnhardt to wedge into the cockpit of his Dallara-Chevrolet during a Thursday stroll through Gasoline Alley: “I think everyone in the paddock is happy Dale’s here, not only commentating but driving the pace car. I was happy to hear that. He’s a great ambassador for motorsports.”

Noting the “genuine” enthusiasm among his peers about having “a legendary name and great personality” with Earnhardt, Team Penske’s Josef Newgarden said, “it seems like this whole competition of who’s top of the heap – ‘We’re better! You guys aren’t great! Our series is more competitive.’ — just seems to be going away.

“It was like that for the last 20 to 30 years, and it’s not necessary,” said Newgarden, the 2017 series champion. “We’re two different types of motorsport, but at the end of the day, we’re all motorsport. They’re equally as difficult and just totally different in a lot of respects. We’re racers. We all like each other. And just to see the respect now that we’re both interested in what each other does, I think we should work together.

“We should all respect each other because they’re both top-level motorsports. They’re all very talented drivers and teams that fill both fields. We should have drivers who want to go run in a stock car from IndyCar and have stock car guys who want to run on the IndyCar side.

“To see this ego and competition between the two get set aside, I think that just benefits everybody.”

Earnhardt, whose Indy welcome Thursday also included a two-seater ride with Mario Andretti, still felt more secure in having his choice as pace car driver be approved by IndyCar’s biggest names.

“I’m glad those guys are so excited to have me there,” he said. “We certainly wanted to make sure that was OK with the drivers before we accepted and make sure they’re OK with that. And they all seem to be on board. The IndyCar guys have a real unique perspective on whatever helps their sport, they seem to all be on the same page. They’re uniquely united in doing anything that helps get more eyeballs.”

United isn’t how the relationship between IndyCar and NASCAR would have been described over the past quarter-century since stock cars began racing at the Brickyard 400.

Jeff Gordon won the inaugural race in 1994 after living in nearby Pittsboro while racing open-wheel cars on his way to stardom, but there was still some Indiana-bred animus about having NASCAR at the tradition-steeped track that had been devoted to open-wheel cars for the bulk of its existence since opening in 1909.

Tony Stewart, the three-time Cup champion who was elected Wednesday to the NASCAR Hall of Fame, has admitted he was one of those Hoosier natives who initially blanched at the idea of stock cars at Indy.

NASCAR on NBC analyst Dale Jarrett recalled a chillier reception in part because NASCAR was rising as IndyCar – which split into rival series from 1996-2008 that damaged its popularity – was suffering.

“We at NASCAR were on such a huge upswing through the early ‘90s and 2000s that I think that even drag racing and IndyCar were being pushed aside and weren’t used to that,” Jarrett said. “And you don’t like to be the afterthought in anything that you’re doing, and I think maybe they felt that a little bit.”

As NASCAR has wrestled with the challenges of audience retrenchment over the past decades, it’s made for more common ground between two series that have had to deal with trying to enhance their relevance in attracting fans.

“Now that things have leveled out somewhat, and NASCAR been humbled a bit over the last decade, that’s changed sort of everybody’s perception,” Earnhardt Jr. said. “But as a driver, I’ve always been interested and curious about not only IndyCar but other forms of motorsport. You want to go see and look and walk around and check out. You want to be welcomed into that world.

“Even at the height of the rivalry or whatever that was, if Mario Andretti or anyone else would have walked down the middle of the garage area, we would have all been like, ‘Hey, holy cow. Welcome! Incredible to have you here!” You just know that’s a race car driver. He’s curious about racing. He’s wanting to see what stock cars are and what they’re about. I think the rivalry has probably been more fan driven than anything else.”

Indeed, more IndyCar and NASCAR drivers have built stronger relationships, some driven by sponsors and manufacturer ties, but others have been formed by authentic camaraderie.

Seven-time Cup champion Jimmie Johnson has become a buddy of five-time IndyCar champion Scott Dixon, and it’s easy to spot the similarities between two low-key superstars whose accomplishments often go unappreciated

“I talk to Jimmie quite often, and there is a lot more crossover talk” of NASCAR and IndyCar, Dixon said. “It’s hard work right now, and everybody knows that. No one has the captive audience. It’s shifting. Everyone is trying to keep up to speed with the changes.

“If we can do it as a group as opposed to, ‘Oh no, we have a bigger following and we don’t want you to take any of ours’ and all that kind of jazz. It’s nice to see the egos have kind of left, and everyone is trying to get on the same page to help each other. At the heart of it, man, we’re all motorsports fans.”

Last Thursday, Johnson hopped an early morning flight to Indianapolis just so he could spend a few hours watching Indy 500 practice.

“I wanted see that place packed full of people and feel the energy that I’ve heard about so many times,” said Johnson, who also texts regularly with other IndyCar drivers such as Newgarden.

“He’s just a racer who keeps tabs on everything that’s going on,” Newgarden said of Johnson. “To get perspective from him on someone who has been in the sport and done so much and been so smart and savvy about it, it’s cool to have that line of communication. Jimmie cares about what’s going on outside the NASCAR bubble. He’s got so many friends in the IndyCar paddock. He knows everybody. He’s poking us and wants insider information on the event to learn more about it, which is fantastic.”

While there was an era roughly five decades ago when A.J. Foyt and Andretti, both winners of the Indy 500 and Daytona 500, regularly would switch between disciplines, racing has become more siloed as today’s drivers became much more limited by team commitments.

There are some rare exceptions, such as Kurt Busch running the Indy 500 and Coca-Cola 600 on the same day in 2014, but crossovers generally haven’t been feasible.

Aside from Indianapolis Motor Speedway, Texas Motor Speedway and Pocono Raceway, the top IndyCar and NASCAR series race at separate venues, which also has contributed to limiting drivers’ interaction.

“I think we’ve just been removed from each other too much,” Newgarden said. “There were two bubbles created, and the bubbles didn’t cross over. We had that for too long, and now that we’re seeing that bridge be created again, everyone is very capable of getting along and enjoying what each other does. I think the IndyCar guys are very open minded to that.

“Maybe we’re more open minded because we got pushed more to the bottom. Stock car had a bigger rise than IndyCar. Maybe we’re more open minded to it because of where we were 10 years ago or so, but that’s not a knock on anyone. We’re all getting closer. Those bubbles are starting to disappear and we’re putting everyone in the same ecosystem, which is great.”

Jarrett, a three-time Brickyard 400 winner, spent last weekend at IMS, witnessing practice and qualifying for the Indy 500 for the first time. Indianapolis 500 pole-sitter Simon Pagenaud was among those who stopped the 1999 NASCAR champion, who considered it “a little bit of a shock” that was recognized.

“Everybody was very nice,” Jarrett said. “There’s only a few of the IndyCar drivers that I really know, but a couple that I had never met or talked to or anything actually stopped me walking through the pit lane. So it was pretty cool to see and be a part of it in their world. A lot of people stopped and talked about NASCAR and the success that I had there. Race fans are truly race fans.”

Many drivers point at potential IndyCar-NASCAR weekend doubleheaders as being the best way to expose the racing to fans of both series.

Power and Graham Rahal are among IndyCar stars who believe they can race Saturday night on the Charlotte Roval, followed by a Cup race Sunday.

“We have to all help each other grow,” Rahal said on the most recent NASCAR on NBC Podcast. “Doing these joint events that only certain tracks can do are huge. We have to do it. We have to build our sports together. To do it independently, yeah, we might make ground here or there, but ultimately we’ll never make enough.”

Because NBC Sports Group broadcasts the full IndyCar season and the final NASCAR 20 races of the Cup season, the tracks on its networks seem the ideal places for the most seamless crossover opportunities. (It worked for The Avengers!) During a motorsports summit in December, NBC Sports executives brought together industry leaders from its various properties (NASCAR, IndyCar, IMSA and Supercross) to discuss how to be more collaborative.

Frye, the IndyCar president, would be a “huge supporter” of an IndyCar-NASCAR doubleheader weekend.

“It could be a cool American motorsports extravaganza-kind of weekend,” he said. “We’ve talked about we’d run a Saturday night, and that Cup stays in its normal spot on Sunday. There are a lot of crossovers with manufacturers and amongst teams. We’ve talked about the friendships we have with them.

“I think it would be a game-changer in a good way. It’s not something you do every week. If you did it once or twice a year. You have to do it one time first. See how it goes. There would be certain tracks we would go to that would fit. At end of day, why not try it? It’s good for NBC, good for IndyCar and good for NASCAR.”

It still could be tricky, though, to avoid the “headliner” status and other ways that could result in one series being viewed as inferior.

“What’s been the reservation from both sides working together is the comparison between the two,” Newgarden said. “And that’s what we’ve got to make sure doesn’t happen. It’s not a competition of which car is quicker. Or which car is more difficult.

“They are different forms of racing. (A stock car) weighs twice as much. The horsepower levels are different. It’s a different art. We’re not there to compare what car is fastest. That’s not what it’s all about, so I think that’s where some of the reservation comes in doing the doubleheader, but I’d love to see it. If anyone is going to win in that situation, it’s going to be the fans.”

Given that possible outcome, perhaps it’s apropos that the latest example of NASCAR-IndyCar harmony will be symbolically led by Earnhardt, who holds sway over more fans than the 33 drivers combined who will be trailing him around the Brickyard at 12:45 p.m. ET Sunday on NBC.

It’ll be quite a sight even for a racer who has seen nearly everything.

“When you look in that rear-view mirror and you don’t see stock cars,” Earnhardt said. “But you see these wild, exotic open wheel Indy cars.

“It’s going to blow my mind.”