【Name: Dark Heavy Oil】

【Description: No refining needed—Dark Heavy Oil powers your train directly. One liter carries your train a fixed distance of 100 km.】

【Appraisal: 1 L/100 km? Talk about fuel-efficient!】

【Because you obtained Dark Heavy Oil, the crafting recipe unlocks automatically!】

【Materials & conversion rate: 1 Magic Crystal, 10 train cores, 1 Fuel Module → 100 L Dark Heavy Oil】

【Note: Fuel Modules can be bought at future Stations or obtained elsewhere.】

"So that's how it works," Bai Cheng murmured, enlightenment dawning on her face.

She'd assumed they'd have to use the crudest, most inefficient method to obtain the oil.

—heading down to the surface to scavenge machine scrap.

But that design would've been absurd.

Not everyone had a Pilot and could shuttle between sky and ground. If fuel were too hard to get, how could leaders keep upgrading their trains?

"One liter of this black sludge moves us a hundred kilometers?" Yu Nian studied the screen, then eyed the reeking can of Dark Heavy Oil, skeptical.

"Still, while we're aloft we can rinse machine parts and collect a fair bit of oil—enough to reach the next Station at least."

Leng Ningxue rubbed her chin, watching Lan Xiaoyu scrub parts nearby.

"We've got about thirty liters, right?"

"Closer to fifty," Lan Xiaoyu corrected. "Every scrap here is coated in Dark Heavy Oil."

"But that's only five thousand kilometers," Yu Nian raised an eyebrow. "Total trip is ten thousand. We've covered one; minus current fuel we still need eighty-five hundred."

"So we need another eight hundred and fifty liters!"

Even Yu Nian startled herself with that number.

"Where are we supposed to find that much?"

Clearly, their only option was to keep moving while scavenging garbage on the ground.

"Tank capacity?" Bai Cheng asked.

"Fifty liters," Lan Xiaoyu replied.

"One refill gives five thousand kilometers of range," Bai Cheng mused.

They'd need seventeen refuels, but to handle emergencies they couldn't let the tank run dry.

Actual refuel count would be even higher.

"Honestly, doesn't feel as economical as a steam train."

Bai Cheng kept silent, staring at the screen and hoping the upgrade's stats wouldn't disappoint.

【Train: gas train】

【Level: lv.1】

【Tank Capacity: 50 L】

【Armored Core: Space Matrix】

【Max Carriages: 10】

【Top Speed: 200 km/h】

【Crew: Crimson, Guardian 3rd-Rank / Purple Iris, King-Rank / Lvdou, Guardian 3rd-Rank / Blue Bird, King-Rank / Huang Yu, Guardian 2nd-Rank / Lan Xiaoyu, Guardian 2nd-Rank】

【Installed Parts: Employee Watchtower, powered railcar】

【Upgrade Requirements: 0/500 Machine Parts, 0/50 train cores, 500 Magic Crystals】

【Note: gas train grants an aura covering 1 km. Within range, all train personnel gain +10% strength and +20% experience.】

【Congratulations—upgraded steam train to gas train! Fixed reward: 100 L Dark Heavy Oil, all crew +10 to every stat!】

The trio blinked in surprise; the train's transformation caught them off guard.

"Didn't think later upgrades would still need Machine Parts," Bai Cheng's brows relaxed slightly.

Leng Ningxue nodded. "Then we can gather fuel and parts at the same time."

With that thought—fuel plus upgrades—their minds felt more balanced.

"And the train's got a range buff!" Yu Nian exclaimed, eyes sparkling. "More experience for us!"

Bai Cheng rolled her eyes.

"Focus on the reward below, will you?"

They'd netted a free hundred liters of Dark Heavy Oil; with current stock the train could travel another fifteen hundred kilometers.

And the +10 to every stat had genuinely made everyone stronger.

"Haven't checked my stats in ages," Bai Cheng recalled. She'd been upgrading items, each granting one free point.

As levels climbed, each minor tier now awarded more than a single point to all stats.

She opened her personal panel.

【Train Conductor: Bai Cheng】

【Level: Guardian 5th-Rank】

【EXP: 39%】

【Strength: 126】

【Physique: 126】

【Spirit: 201/999】

【Talent: cheng book】

"Huh?"

She'd been dumping every point into Spirit, so it had long surpassed the other stats, now topping two hundred.

"What's the 999 cap?" Bai Cheng wondered. "Is that the limit?"

Seeing a tooltip, she tapped for details.

【When any single stat reaches 999, transformation occurs—key to final promotion and the secret of the world core...】

Bai Cheng was speechless.

The system was selling her dreams again.

Still, the message hinted that maxing a stat was crucial to breakthrough.

She doubted it meant her current Guardian promotion; it had to be the abnormal tier «N.o.v.e.l.i.g.h.t» above—King.

Beyond King stood Emperor, the world's peak and the system's apex.

"So it's about breaking into King rank," Bai Cheng mused. "I'll need to farm stats and max Spirit as fast as possible."

Only she could farm stats; it couldn't be the sole path to King.

How else could her crew advance? They didn't even have stat points!

"Xiao Cheng?" Yu Nian waved a hand in front of her face. "What's on your mind?"

Bai Cheng snapped out of it and shook her head. "Nothing. Let's move."