[TinCanSailor]

If you catch it before a bearing seizes or is spun you should be good to go. There is the issue of the floating metal that has come off the bearings potentially accumulating in the vanos solenoids, oil cooler, oil spray nozzles or other areas. 4 new vanos solenoids will be about 1200 if you need them and are replaceable without engine removal. On the more costly side would be damaged rods or pistons. The rear cylinders see a lot more heat due to the downpipes and turbos sandwich them in with all that heat.

See if you can get some cold start audio/video and some audio of it idling after the engine kicks down rpm post warm up. My work has me in a spot so I won't be able to listen to it but am pretty sure if you post it here or in the F10 M5 Forum /Engine sub forum you'll get some well tuned ears to listen to it. Hit youtube for some videos folks have posted of their s63tu engines with bearing and rod noise.

These cars do consume oil much like the N63tu's do but mine has not been as bad as my M6 has not been as bad as my wife's 550. That said you might be getting to a point of needing pre-cat o2 sensors. I think the pre cat o2's are about 200 each.

Have them check the battery date if they can. It will require pulling the trunk mat out and depending on the battery they may have to lift it out to see the date. It is about 240 dollars for an aftermarket battery.

Also have them check the fluids levels in the turbo coolant reservoir and engine coolant revivors. Low levels or any obd codes could be a good indicator that turbo coolant lines have leaked into the top of the engine externally. Low fluid means they have dealt with more heat and heat is the mortal enemy of these engines.