Every Tesla electric car built since late 2014 has the necessary hardware for Tesla's "Autopilot" suite of semi-autonomous driving features.
But not every customer opts to pay the $2,500 to enable the system as they order their car—although owners can still pay $3,000 to add Autopilot after they take delivery of their new electric car.
Now, to encourage more of them to do that, Tesla is offering a one-month free trial of the Autopilot system.
DON'T MISS: Tesla Autopilot: The 10 Most Important Things You Need To Know (Oct 2015)
Just as with satellite radio, or telematics systems like General Motors' OnStar, owners will get a chance to test the system's capabilities before they commit to the full purchase (or monthly fee in the case of the telematics services).
Tesla is telling customers about the offer through notifications sent to the cars' central touchscreen displays.
Customers who opt into the free trial will then receive an e-mail telling them how to add Autopilot permanently.
Tesla Autopilot sensor system
If nothing else, the free trial demonstrates the flexibility of using software to control major vehicle functions.
Tesla already addresses bugs and adds features with over-the-air software updates, and now it can let owners try them out too.
That may be particularly useful for Autopilot. It's an expensive option, and one that Tesla considers to still be in "public beta" form.
Autopilot launched in October 2015 with Version 7.0 of Tesla's operating system.
The features available at launch included adaptive cruise control, automated steering, and an automatic lane-change function.
This allows drivers to initiate a lane change by simply flicking a turn-signal stalk. The car does the rest, in ideal conditions at least.
2016 Tesla Model S
Tesla strongly recommends that Autopilot features—in particular the auto-steering function—only be used in good weather on roads with clear lane markings.
Not all drivers have heeded this advice, leading to some close calls that have made excellent YouTube fodder.
In January, Tesla added "Summon," which allows a car to maneuver itself into and out of parking spaces without a driver onboard.
The feature does not work in parallel spaces, and only allows cars to pull forward or backward.
Tesla CEO Elon Musk has said Tesla will continue to develop this technology until cars can more or less drive themselves point to point.
He believes regulation will be more of a hurdle than the actual technology, which he estimates will be ready in the next few years.