General Motors aims to turbocharge its non-vehicle revenue by introducing dozens of new fee-based digital features by 2026, including one enabling a car to predict when it will need maintenance, a top executive said on Thursday. “We have 50-some value-added products and services that we’ll be rolling out over the next 36 to 48 months,” Steve Carlisle, president of GM North America, said at an investor conference. Carlysle said GM’s OnStar unit, which now offers insurance in addition to concierge services to drivers, generates about $32 a month per customer, and its enhanced Super Cruise driver assist feature will further bolster that. The new digital products, including in-vehicle subscriptions, will be supported by GM’s Ultifi software and connectivity platform. Ultifi also will enable over-the-air software updates, and help drivers and passengers with tasks such as online shopping. Carlysle said some of the digital features are designed to take advantage of …