One disc is enough, all six not necessary. Sounds like you are installing the disks upside-down possibly? Try flipping them. June

Choose the engine that is the same. The 3.0 T6 engine came in three variants. B6304T2, Or B6304T4, and the Polstar B6304T5. I'm quite sure all three use a intercooler? June

My S80 T6 runs Redline synthetic 5W-30 year round since 2016 or 17 3K oil change. Before that, I always opted for the synthetic dealerships use 5W30 the cooler couple months and 10W30 Summer as Volvo requires for the 2004 2.9 Twin Charged T6 engine. Volvo required via the maintenance schedule 5K oil...