NASCAR preseason testing is a giant tease in that it provides tantalizing hints of what’s to come, but the information is often incomplete.

Take this two-day organizational test in Las Vegas, for example. There were 13 cars on track, draft-racing for 25 laps at a time with temperatures in the low 60s. Will those sessions look the same when there are 40 cars driving a full race in warmer weather next month? Of course not.

So let’s focus on what we know for sure after this test at Las Vegas and the three-car Goodyear tire test at Fontana last month. When it comes to the new rules package, what can we write with pen and what remains in pencil?

Here’s the first, most obvious, most indisputable fact about the 2019 package: It signifies a mentality shift in NASCAR that had been in the works for years.

This isn’t a small tweak to the racing, like the addition of the free pass. This isn’t even on the level of breaking up the races with stages or implementing double-file restarts.

This package — which brings drafting to the Cup Series on a widespread level — is a fundamental change in the way NASCAR races will look and feel.

By placing a priority on entertainment, officials have crafted the racing to produce a show they hope will thrill and excite the fan base. Ten-second leads are dead, raw speed has diminished importance and the outcome of races will more often be in doubt.

“We want cars close together, we don’t want people falling off and going laps down, we don’t want people checking out,” NASCAR vice president of development and innovation John Probst said. “We don’t want that ‘wall of noise’ (where the cars are spread out and just going by the stands continuously).”

By keeping the cars from escaping one another, the demand on the drivers will change. This won’t be about the bravery of driving into the corner deeper than another competitor, but rather about understanding the draft and making moves to find pockets of clean air — and thus gain position.

Many of the drivers, as you can guess, hate this. They’re trying to be restrained in public, biting their tongues or talking around their real opinions of the package. They save their griping for private, believing it does no one any good to blast it within earshot of fans.

Well, for the most part.

“We’ve taken the driver skill away from the drivers in this package,” Kyle Busch said. “Anybody can go out and run around there and go wide open. You (media) can probably do it. It’s going to be a lot more mental game, a lot more chess match, thinking how you make moves, how daring you’ll be.”

Many of those who view themselves as “racers” in the garage feel the same way, grumbling the new rules go against the traditional spirit of motorsports.

NASCAR is well aware of the opinions, of course. Probst acknowledged the majority of drivers dislike the package (and wondered aloud why they would openly say it doesn’t take skill if drivers are paid for those very talents). But officials pushed forward with this approach in hopes it would make for a better on-track product.

In short, if Cup cars race like the Truck Series, it will be deemed a success in the halls of NASCAR. After all, fans have long claimed Truck racing was the best NASCAR had to offer. NASCAR took that as a hint.

So will it work? That’s where the pencil comes in and the pen disappears.

The short answer: I don’t know. You don’t know. The drivers don’t know. NASCAR doesn’t know. No one knows for sure, and anyone saying otherwise is just guessing.

However, there were some hints at the Vegas test. And the results were mixed:

— Could the cars stay closer together than before? No doubt. However, Vegas is a relatively smooth, fast and low-wear track. During the drafting sessions, the leader could hold the gas wide open all the way around the track — but the cars in the pack had their hands full and often had to lift, depending how their cars were set up. That won’t be the case at a place like Fontana, where the tires were making a considerable difference at the three-car test and even the leader had to lift after six or seven laps.

— Could the leader get passed? Through the five draft sessions in Vegas, it looked quite difficult to achieve. If a driver had even a half-decent car, it appeared clean air would leave them untouchable as the second- and third-place cars scrambled to try and get by. The action in the field was good, but for the lead? Not so much. But again, that’s at a specific test with specific circumstances that might not apply everywhere — so we just don’t know yet.

— Did this package take some engineering out of the cars? Maybe in some ways, but now crew chiefs and engineers will just have a different challenge. They can trim their cars out to be fast but perhaps not handle well or set up to have a good long-run car but sacrifice some of the drafting speed.

— Will this change the strategy? Big time, and moreso than we can even grasp. With track position looking like it could mean more than ever, crew chiefs might have to take huge gambles on tires late in a race. Pit stops will be absolutely vital; a pit-road penalty might doom someone’s race. And there might even be some wrinkles we can’t yet anticipate, such as drivers teaming up to bump-draft in order to pass the leader.

Let’s go back to writing in pen for a moment, because we know this much for sure: As it stands now, this will be one of the most unpredictable seasons NASCAR has ever had. Between the new package and the playoff format, trying to come up with a field of 16 playoff drivers — let alone a championship pick — will be more like wild guesses.

There will likely be drivers who make the playoffs based on a Hail Mary call to stay out at the right time, while others who benefit from races filled with attrition from the additional crashes that will take place this season. There will be spectacular wrecks on restarts and highlight reels filled with daring, aggressive moves for the lead.

Will the new package save the sport? No, because no one thing will. Will it increase interest and attendance, or at least stop the slide? That’s the potential payoff for this gamble, and officials have decided betting with the sport’s integrity itself is worth the risk in order to entertain its fan base.

Good or bad, the verdict won’t come anytime soon. Only two of the first six races — Vegas (March 3) and Fontana (March 17) — use the full version of the new package, and it will take much longer than that to measure the impact.

In the meantime, drivers, fans and media alike will look for signs, wondering if this new Entertainment Era will lift the sport or only drag it down further, as some have seemed to predict via social media.

For NASCAR’s part, officials are just hoping fans give it a chance.

“I would encourage them to give it a chance and see it and watch it,” NASCAR’s Probst said. “I think they’re going to find it will be very entertaining.”

John Probst said NASCAR officials were pleased with what they saw in the Vegas test, but said they aren’t ready to celebrate yet.

Watch: Periscope broadcasts of the 2019 rules package test at Las Vegas