Hey, looking for some purchasing advice.

Found a stock 2005 RX-8 on FB market with the OEM engine at 75k. Decided to get it compression tested by my local Mazda Dealer and these are my results. Not entirely sure what to make of them.

Rotor 1: 130/120/120 psi

Rotor 2: 91/88/89 psi

Both @ 200 RPM

As far as I can tell, the first rotor is actually pretty great. As for the second one, it seems not as great, but not quite within failing range.

Guess I'm mainly wondering if this difference between the two rotors is something to be concerned about? From some searching around the forum it seems like the gap between rotors is usually smaller. Could I expect an RX8 in this condition to still have some life left if I do not drive it very often and take proper care of it?

 

The Mazda dealer has a chart to qualify these results. That's definitely more of a gap that I'd expect and possibly enough difference to fail the motor. [edit: yes Mazda spec requires no more than 14psi difference between rotors. You have 30]. But I also don't believe the front rotor numbers. 130 at 200rpm is way above factory spec, which is hard to believe at 75k. The second rotor is borderline. You might make it to 100k with this engine before symptoms show up, you might not.


Mandatory Compression Test

How much is the seller asking for the car? It might be worth it if you plan out your replacement engine, you do have time. Given how old these cars are getting, it's often better/cheaper to buy one that has already had the engine replaced with a known good one, or buy a non-runner on the cheap and add your engine.

 

walk away. This engine will require a rebuild to fix the low compression rotor. Only good news is you only will have to get parts for one rotor.

 

Is it safe to say that the "actual" rotor 1 compression is likely closer to the rotor 2 value considering how far above spec the recorded values are? Maybe Mazda did something odd with this test.

The seller is listing $7200 CAD (or about $5400 USD), but I think I could probably offer less if I raised some of these same concerns. Unfortunately the market around here tends to overvalue just about anything, cars with much higher mileage still go for upwards of $6000 CAD.

 

I've seen this happen before where one rotor was great and the other was crap. Its such a difference that it would be worth it to rebuild. But for the money, you should be able to find something better. You don't want to drop $6k then another $4k+ rebuilding the engine. Milage is irrelevant in this car due to how common rebuilds are. You really want to make sure the car is in overall good shape with good compression results.

 

^^ this
7200 CAD isn't crazy for a good condition 2005, but not if it costs you another $5k-6k in new engine over the next couple of years.
You can get a much more recent, better condition RX8 for 7200+6000.

That's why the best value is an RX8 that sells at market rate (same 7200), but with a new engine. All the work is done and the past owner swallows the cost of engine replacement. Next best is heavily discounted RX8 with a dead engine, which you then give a new heart.

I know "engine replacement" sounds drastic on any other car, but that's totally normal on rotaries. It's not a sign the car is at end of life, if anything, it's reborn.