What could it mean?

Hello, engine performance concerns seem to be present. Hands on testing is going to be needed to figure out what is happening. Using a diagnostic tool to monitor component operation to see where the loss of power is originating from may be helpful. A basic check of fuel, air, ignition spark and emissions controls is needed. An engine compression test may be helpful, as you stated some kind of oil consumption concern possibly, as well as smoking. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops