Jimmie Johnson is in a long-term relationship.

Yes, Johnson has often spoken of the support he’s received from wife Chandra, married since 2004.

But for all of his statistical accomplishments, including a record-tying seven NASCAR Cup Series championships and 80 victories heading into Sunday’s Camping World 500 at Phoenix International Raceway, none is more impressive — or unimaginable — in a volatile sport/industry than this:

Since 2002, his first full season, Johnson has had the same team owner (Rick Hendrick), the same crew chief (Chad Knaus), the same sponsor (Lowe’s), the same car chief (Ron Malec) and the same automaker (Chevrolet).

Rules, tracks, competitors, car specifications, championship formats and countless other variables over 15-plus seasons have been changed more often than the Valvoline in Johnson’s engine. Remarkably, however, not Johnson’s key ties.

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Especially that with Knaus, his friend/strategist/coach/confidant over NASCAR’s marathon 36-race Cup season, which demands thousands of communications and decisions between driver and crew chief. History teaches it’s not unusual for these emotional and intense roller-coaster relationships to have the shelf life of a banana.

They are now a hyphenated entity — Johnson-Knaus — inextricably bound by their success together and as they chase NASCAR’s greatest historical touchstone, an eighth Cup championship.

“As our sport evolves, the only consistent (element) is our relationship,” said Knaus, trying to set a NASCAR crew chief championship benchmark of his own.

Johnson and Knaus admit to their share of spats, including several during a winless and struggling summer of 2016, which seemed to make a championship run unlikely. Hendrick, shockingly, conceded he wondered if the duo should split: “Is this (the) time? Do we need to make a change?”

But Johnson, after starting last, tied the title totals of Richard Petty and Dale Earnhardt with a victory in the season-finale at Homestead-Miami Speedway.

“We’re definitely like brothers,” said Knaus, 45, whose ultra-competitive demeanor makes many regard him as the sport’s biggest workaholic. “The closer you get with your family, the more you can go through anything together. As much as we’ll fight and battle and argue from time to time, if somebody steps up and pulls him around, I’m going to sock the other guy in the nose.

“All I want to do is see him be successful. I think that’s probably the biggest reason why we’ve managed to stay together.”

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Johnson, 41, known for his calm public persona, says they’ve learned from the relationship of their former Hendrick teammates Jeff Gordon and Ray Evernham. The landmark Gordon-Evernham combination won three Cups and 40 races in a four-year stretch but split before the end of the 1999 season.

“I’m loyal,” said Johnson, who has four PIR victories but only a best 11th-place result in three 2017 starts. “I’ve been accused of being loyal to a fault. The respect we have for one another has always been the glue.

“Chad and I look at what Ray and Jeff went through. We’ve had both of them tell us, ‘You can work through your problems. If we would have stayed together, who knows what we could have done?'”

Knaus, who married in 2015, describes some of his arguments with Johnson as “painful” and that “nothing is out of bounds.”

Now part of NASCAR lore is Hendrick’s late 2005 “milk and cookies” meeting with his driver and crew chief, which, perhaps, made the championships possible. The Johnson and Knaus egos were colliding in frustration after four seasons (2002-05) in which they won 18 races yet finished fifth-second-second-fifth in the point standings.

Hendrick called them into his office and said, “If you’re going to act like kids, we’re going to have some milk and cookies,” and there they were, a table.

“I told them they were so close to success and they’d be fine if they’d just talk things out and get their problems out in the open . . . That broke the ice.”

The next year they won the first of an unprecedented five consecutive Cups.

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And about that eighth championship?

“Yes, I would love to do that,” said Knaus, who then tellingly added, “but I also would rather get nine.

“The way we operate is different. We don’t necessarily set goals and try to eclipse other people’s records. We set the goal to try to go make our own records. We want to win our next race. We want to be on pole for our next qualifying session. That’s how we approach life.”

Johnson said he’s “really been enjoying (title) seven,” and part of that has been spending time recently with his wife and two young daughters at their second home in Aspen, Colo., away from NASCAR’s Charlotte-area hub. “I’m trying to keep eight in a very fun and light-hearted place.

“In my younger days, I was very good at over-thinking things, and applying too much pressure on myself. The fact that I’m chasing this history, I’m not going to put extra pressure on myself to do it.”

Do it or not, it will be a Johnson-Knaus effort.

“I firmly believe,” Johnson said, “the relationship between driver and crew chief is where the magic lies.”

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NASCAR week at PIR

What: NASCAR Monster Energy Cup, Xfinity series races

When: March 17-19

Where: Phoenix International Raceway

Tickets, information: phoenixraceway.com

Schedule

March 17 (gates open 10 a.m.)

Xfinity practice, 10 a.m.

Monster Energy Cup practice, 11 a.m.

Xfinity practice, 1 p.m.

Monster Energy Cup practice, 11 a.m.

Monster Energy Cup qualifying, 4:45 p.m.

March 18 (gates open 9 a.m.)

Monster Energy Cup practice, 9 a.m.

Xfinity qualifying, 10:05 a.m.

Monster Energy Cup practice, 11:30 a.m.

Xfinity race: DC Solar 200, 1 p.m.

March 19 (gates open 8 a.m.)

Monster Energy Cup race: Camping World 500, 12:30 p.m.