SAN FRANCISCO — Tesla recently started offering subscriptions for the capabilities it dubs “Full Self-Driving,” making a $10,000 upgrade accessible to buyers for $199 per month. But even Elon Musk isn’t sure drivers should opt in yet.

“Right now, does it make sense for someone to do an FSD subscription?” the Tesla CEO asked on Tesla’s quarterly earnings call Monday. “I think it’s debatable.”

It was an eyebrow-raising moment on an otherwise routine earnings call, a forum for analysts and investors to pepper executives with questions about company matters. Musk admitted he doesn’t think the new product makes for a compelling “value proposition.”

Meanwhile, he announced Monday could be his final regular appearance on the quarterly earnings calls, where he offers colorful commentary on company matters and even veers into spontaneous rants. Last year, he used the forum to take aim at government-mandated shelter-in-place orders, urging officials to give people back their “freedom” in a profanity-laced tirade, citing shutdowns as a financial risk for his company.

But the comment about Full Self-Driving, which was hailed with astonishment on Twitter, might have been the final time Musk would stick his foot in his mouth in this particular forum.

Tesla has offered the hardware since 2016, promising that if owners opted into the features, their cars would eventually be able to drive themselves. It has rolled out the ability to navigate city streets to a limited group of beta testers through an early-access program. But the software is in development, and owners often document instances of cars failing to properly navigate obstacles, requiring owner intervention. Tesla has been criticized by safety advocates and industry competitors for deploying it on public roads.

Two men died after a Tesla vehicle, which authorities said was operating without a driver, crashed into a tree in a Houston suburb on April 17. (Reuters)

Full Self-Driving builds on Tesla’s advanced driver-assistance system known as Autopilot, which has included features such as the ability to navigate from highway on-ramp to off-ramp, and park and summon the vehicle on its own. With Full Self-Driving, an owner could choose to navigate on autopilot and monitor the vehicle as it makes a full trip between locations without driver intervention, in ideal circumstances.

But Musk has repeatedly talked about the difficulties of automation and the practically endless stream of challenges the company faces in making vehicles drive on their own. Regulators regard Tesla’s software as a driver-assistance system, meaning the operator must pay attention at all times.

Musk said on the call that even though Tesla is selling Full Self-Driving capability to consumers now, it’s up to the company to convince users to opt in. Tesla says on its website the $199 subscription buys the “capability,” meaning the owner does not immediately receive the latest Full Self-Driving upgrades but rather the ability to obtain them.

“We need to make Full Self-Driving work in order for it to be a compelling value proposition,” Musk said, adding that otherwise the consumer is “betting on the future.”

His comments seemed to imply that by subscribing to Full Self-Driving right now, Tesla owners are doing just that.

Tesla posted a more than $1 billion profit after delivering more than 200,000 vehicles in the second financial quarter, a record for the electric vehicle maker.