My 2011 R3 just passed 97k miles and, knock on wood, has no identifiable problems. I anticipate keeping it as my DD (and my family's only car) for the foreseeable future. So, I'm feeling out ideas for preventative maintenance over and above the stuff in Mazda's maintenance schedule. Let's say I can spend up to $500 and prefer OE parts.

Engine was replaced under warranty just before 75k miles, along with the clutch kit, one motor mount, and whatever else comes with a Mazda engine replacement (water pump, coolant, etc.). Cat was replaced under warranty about 20k miles before that. Tires, brakes, coils, plugs, wires, oil, filters, etc. have all been serviced/replaced on normal-to-aggressive schedules. Otherwise, everything is original and has been looked over by a (good) Mazda dealership at least once a year.

I'm thinking I should do the front O2 sensor, partly as a matter of course, and partly because I think my fuel economy might be on a slight but noticeable decline. Does that make sense? Anything else I should look at?

 

I'm at about 114K on my 2009 R3. Also my DD, but apparently this is my 2nd RX-8 with a better than average motor as it's the original. I have no clue what the compression is but don't have any warm start issues, so ignorance is bliss. Assuming hoses and belts were replaced when your motor was swapped. If not, you might want to do that. On my first RX-8, I replaced my coolant overflow tank at about 100K (stuck sensor). While doing that, the nipple on the top of the radiator that it's attached to came off with very little force applied. The end tank had become very brittle. So I ended up also replacing the radiator. I'm planning to change out the radiator on my R3 in the next month or 2 based on that experience. I also pre-mix. Admittedly, I could just be throwing away money on that but my first RX-8 went 147K on original motor (compression was on the low end of scale but still passing and car had no warm start issues) and as mentioned the R3 seems to be fine.

Only other thing I can think of is corrosion. Might be worth it to pull out your wheel well liners and give it a good look and address anything you may find.

 

Why was your cat replaced - how did you know it was an issue?

 

I'd leave the O2 alone. Modern ECUs, including RX8's, run diagnostics on sensors and can recognise when it's out of spec. O2 sensors lose responsiveness, but they don't lose really lose calibration until much later. So it'll still measure the correct AFR, but when AFR changes, the sensor is slow to respond and the ECU's routinely tweak the mixture to check for that.

I'd focus on soft aging plastics and rubbers: rad hoses, coolant tank, radiator end tanks. Weather seals and gutters. Wipers.
Suspension bushings, bump stops and shock mounts. Especially the sway bar endlinks, they can get wobbly with time. Make sure you test them with car level
Wheel bearings and ball joints.
Oil cooler, condenser and rad fins.
Brake slider pins, brake fluid and piston seals, handbrake mechanism.
Coils & Cat

Doesn't mean you need to replace all of these, but examine thoroughly.

 

FYI Fodi's car was totaled recently, but he made it out unscathed. He joined the BMW club

 

Physically unscathed, anyway.

The fact that the crash happened not too long after this thread is one of the things that still hurts. :/

 

is your car totaled? details?

 

Yes, he posted it in another thread.

https://www.rx8club.com/lounge-4/goodbye-r3-268751/

I wouldn't ask for any details if I were you. He's not that comfortable talking about it.