Turned over 209,000 miles last week on my 04MCS, and decided to do a compression test.
#1 143 Lbs
#2 140 Lbs
#3 133 Lbs
#4 143 Lbs

Bentley manual shows a range of 131Lbs to 196 Lbs.
Soooo.....time to ponder the options.

Oh! Still on the original supercharger,too! Have had a 15% pulley on for about 185,000.

Jim

 

209K miles in 6 years without major issues is a good one but wear and tear on the rings is now showing per your compression numbers. Mine is also an 04 but only 21K and just recently took dry compressions at 176, 175, 170, 173. My car is low mileage but I drive hard and spirited when road is safe.
Yea, it's time to rebuild yours before damage is done. ABF? Endyn?
BTW, how often did you change your oil and what type/brand because there is probably a lesson to learn from your good experience.
Tks. for sharing.

 

Did you ever service the SC at all? If not, that's promising.

 

Yes, what kind of oil? Synthetic? What brand?

 

I've been using Redline or Royal Purple, and NAPA (Wix) filters.
Usually change oil at 7500-8000.
Never serviced the supercharger.

Jim

 

my '04 MCS at 60k miles

150, 145, 145, 145

same car at 128k miles

160, 130, 130, 160 - from Turner Motorsport
165, 158, 158, 170 - from Mini of Peabody

note that the two measurements at 128k were taken on adjacent weeks, so the very different numbers should tell you something about the variances in approach and tools that can accompany compression testing, even by qualified technicians

the rest of the story can be found at the thread "Resetting the odometer the hard way", but the punch line is that I put in a crate works motor and new supercharger at 130k miles.