650 S ABS burning 1qt oil every 500 miles

Yeah you can buy oil almost anywhere but it shouldn't use oil like that. Everyone used to make jokes about the Friday end of shift American cars back in the 60's and 70's related to finish quality being poor but I've discovered that the Japs aren't infallible.
Had a 1978 Dodge/Mitsubishi D50 pickup truck bought used, 30k miles, back in 1980-84, used oil from the time I bought it. As the mileage added up, around 50-60k, I noticed that oil consumption while never good had increased to where I was adding a quart every 200 miles then it started running poorly. Did a compression check and the front cylinder was way low.
Discovered the 3 piece oil control ring on the front piston, two wipers and one expander, one of the wiper rings was never installed. Over many miles the expander ring had pushed out and polished marks up the bore and the rings would no longer seal properly causing oil usage which lead to a burnt exhaust valve.
My rebuild shop looked at the block and told me that there was no appreciable wear in the bore but that Mitsubishi used hard chrome rings which will only seat properly in a perfect bore. If I would hone it enough to put a cross hatch on it and use Hastings cast iron rings it should seal fine without having to pull the engine and rebore that hole. I did that and it worked just as he said, drove it for another 100k miles with only a quart of oil usage between changes, 5k miles.
In my opinion bad valve guide seals alone isn't enough to justify the amount of oil consumption that you're experiencing. I hope they can get you sorted out to your satisfaction.