2003 w/133,000 miles. The first three cylinders were 210-215 , I did three times each cylinder. But the 4th cylinder was 220-235. So I'm wondering why is it like this? I used a brand new compression tester from Advance Auto parts and did not use the adapters that were included in the compression kit. Could that be why?? Thanks

 

It could be so many reasons (such as more oil sealing the rings in that cylinder or better valve seating), but those numbers are flat-out awesome for 133K miles

 

Compression in my 4th cyl was a little higher than the rest. On my 2003 s2k w/ 118k mi. compression numbers were 220-225s average for 1-3 and 230 for 4. I let the engine turn over 6 times per cyl.

 

I would be happy with these numbers even on a newer motor. Have do a leak down test yet? Why are you looking at this at all, are you having an issue?

 

yea I dynoed the car and made about 187whp and it was lower than what I was expecting. So someone suggested that I should do a compression test.

 

187 is really not horrible this time of the year in a lot of places. Temp, humidity, and altitude have a ton to do with it. It varies from place to place so be sure to ask the tuner what he thinks but you might be spot on. Most ap1's are in the mid/low 190s so you are pretty close.