tuj

When I first got my car, this was the compression (sorry I do not know the RPM they tested at, I assume ~260):

f: 7.8, 7.4, 8.1
r: 7.2, 7.6, 8.0

Now I am at 54k miles on the car and just got a compression test done again, this time *with* the RPMs. At 267 rpm:

f: 6.9, 6.7, 6.6
r: 6.4, 6.4, 6.3

Thoughts on how the engine is aging? I don't really know how good or bad these numbers are, so help me out please. I'm surprised there was that much drop. The dealer told me that anything over 7 was 'like new'.... Not sure I buy that....

Jon316G

iTrader: (1)

I had to convert this to PSI for me to visualize easier
Since you didn't know the RPM for the first test, I'll just use the 267 from the 2nd test (unless you upgraded the starter since).

f: 7.8, 7.4, 8.1
r: 7.2, 7.6, 8.0

Converted to PSI (rounded):
F: 111, 105, 115
R: 102, 108, 114

Normalized to 250rpm:
F: 110, 104, 115
R: 101, 107, 113
--------------------------------------------------------------------------------------------

And this is your latest compression numbers:
f: 6.9, 6.7, 6.6
r: 6.4, 6.4, 6.3

Converted to PSI (rounded):
F: 98, 95, 94
R: 91, 91, 90

Normalized to 250rpm:
F: 97, 94, 93
R: 90, 90, 92
--------------------------------------------------------------------------------------------

Standard: 120psi @ 250rpm
Minimum: 98.6psi @ 250rpm

Looks like its time for a new engine!

tuj

wow you are kidding me....I'm on the way out aren't I? 'Normal' wear? Or something perhaps worse?

Thank you for converting and normalizing the numbers, all I got were two camera photo printouts of the tester from the dealer.

I bought my car in late 2004, am I still under the warranty? My dealer told me these numbers were "fine", so how do I go about telling him otherwise (btw, I had to explain what a 'face' of a rotor was to the manager....sigh, and this is Mazda?)

Jon316G

iTrader: (1)

The car will likely still run fine... its just under Mazda's minimum tolerance.

The engine core is covered for 8yr/100K miles

You can keep driving it until you notice power loss and/or hard starts (or you're close to warranty end).
Then worry about that argument... which the numbers will probably be less and they may not argue with the readout.
But you can always ask them why they say its fine when Mazda's tolerance is 8.5 standard and 6.9 minimum.

tuj

Any theories as to how this happened? I have always kept the car full of oil, I have always let it warm up before taking it above 4k rpms. I've done all my oil changes on or ahead of schedule.