The Cadillac CT6 currently serves as the luxury brand's flagship sedan, but its long-term future remains uncertain. It's not being discontinued just yet, but already there appears to be some powertrain changes. More specifically, there are now fewer options available.

According to Cadillac Society, the automaker has quietly discontinued the turbocharged 2.0-liter inline-four engine. Cadillac has not made an official announcement so therefore we don't know exactly why this base engine is being given the boot. We have reached out to Cadillac seeking comment and will update this space if we hear back. For now, there are a couple of theories. First off, Cadillac could have simply decided its biggest sedan shouldn't have this smaller engine.

The CT6 was the first full-size Cadillac to have this engine type. Or, and this sounds more likely possible, this engine is being used in a large number of other GM vehicles at the moment. Demand for it is high and GM could have decided to allocate the engine to other vehicles that need it more.

Remember, the CT6 still has three other engines to choose from: the naturally aspirated 3.6-liter V6 with 355 hp and 284 lb-ft of torque; the twin-turbo 3.0-liter V6 with 404 hp and 400 lb-ft; and the twin-turbo 4.2-liter Blackwing V8 with 500 hp and 574 lb-ft. The turbo four-banger is rated at 237 hp and 258 lb-ft, which really isn't a lot compared to the other engines.

But the loss of the turbo four also means another loss for the CT6: rear-wheel-drive. See, all other powertrain options are all-wheel drive only. A new 10-speed automatic transmission is standard with all engines. The apparent discontinuation of this turbo four comes only several months after it was introduced on the CT6. It replaced the last-generation turbo 2.0-liter four.

For now, the turbo four elimination appears to be limited to the US, but we wouldn't be surprised to see it extend beyond our borders to other countries and regions where the CT6 is sold, including Mexico, China, Korea, and the Middle East.