Only run premium in the Summer? What a truck load of BS. I would demand to see that gas so you can take a sample to the gas station for reimbursement if that is true. But I suspect it's dealer bullshit.

https://cimg2.ibsrv.net/gimg/www.rx8...6dd02b9eaf.jpg
Here's the actual Mazda dealer invoice and the gas sample that took some time to materialize. Help me with their logic:
(1) PREMIUM fuel should not be used (owners manual states premium is required)
(2) car was found to be running 15% lean (wouldn't excessive alcohol in fuel cause it to run rich)
(3) gas sample took 11 minutes to show up after I asked (hmm...and no test data available)
(4) gas sample appears to have a large volume of water in bottom phase (how did the car run?)
invoice from today's dealer visit

https://cimg3.ibsrv.net/gimg/www.rx8...918c25d114.jpg

bad gas from my running 2010 GT

Yes, more E85 would lean out the mixture. It does look the way water looks in fuel though. But who knows with some tech trying to prove a BS theory.

The reason I took the car to the dealer was to confirm issues with the cat (glowing on top). Now I'll have to invest in a better OBD-II reader to monitor a bunch of functions and hope the cat throws a code before the dealer spends even more money on a new cat and engine under warranty.

Would premix cause any of this from a fuel standpoint or taxing the stock cat more?

I'm not sure about premix... and I rail the shit out of my 8 once it gets warm... annnnnnd as far as premium fuel goes we max out at 91 out here in good ol' Colorado... sooo I don't know what to tell you aside from horse shit. Granted, I'm no longer running the stock cat and I premix.

correct E85 is leaner but the sensor would then way over enrich the fuel to air to get stoichiometric right. The dealer said that this so-called E85 leaned the mixture.

I was doing that yesterday. Just cruising around I was seeing mid 1300F to Mid 1400F EGT temps. One quick pull in second to about 6500RPM in second and the temps shot to low 1600F. My 09 R3 has 90K miles now, I have a RB DR midpipe that just waiting to go on when I get time to do it.

OP, spot on advise from 9K, as always.
He will always look out for you and others, just don't muck him around.

I drove my 8 to work this morning and logged the trip in Torque. Ambient temp was 48F. Shift points were around 5000 RPM. The trip was 20.5 miles of city driving, with many stop lights, and top speeds reaching 55mph.

As you can see, just daily driving an 8 produces EGTs high enough to kill most cats, assuming Magnaflow's operating temp of 1200F is to be believed.

https://cimg7.ibsrv.net/gimg/www.rx8...191ba283df.png

Yeah the ECU would try and correct but it would take a lot of E85 to really lean it out since it is so rich on the factory map. And like I said, with straight E85 or even a large quantity of it, it would not run or would sputter and stall and just run like shit.

I really have to monitor my E85 mixture because "E85" can be anywhere from E50 to E85 depending on the station and when mine is off, the car runs like shit since it is tuned for it. I use the same station test it fairly often.

What are the requirements for inlet and outlet gas temps and other specifications for the RX8 cat to say whether a cat is failing or has failed?

A quick update that still has me questioning the dealer's diagnosis. I called and talked over the issues with the Service Manager and the techician who worked on the car - net I'm still suspecious that this $99 diagnosis was run up for extra cash to meet the "weekly quota" on income.

PREMIUM - dealer still stands behind that PREMIUM gas in an RX-8 is overkill especially in Winter (lie)

BAD GAS - they mentioned that they used water to determine that the gas was very high in ethanol near E-85. Milky organic (gas) phase indicated to them that the gas was high in ethanol content. No quantitative measures no record of the ST/LT fuel trims nor exhaust temperatures were recorded in their system. In my line of work, no data is just that.

I will invest in better tech to monitor the health of the catalyst and the car and do it more myself. I'm not going back to that Mazda dealer, even for an oil change. They made $250 extra on me and lost a client. PM me if you want to know what dealer this was (or look closer at the invoice).

Yeah man, it's BS. They are just so used to taking advantage of people who don't know shit.

As for the temp range, I am not sure but if the difference is significant, then I would say the cat is bad from what I have seen because it just means that the heat is staying in the cat.

BTW rotarheads - mazda has an email address to address complaints: MazdaCustomerExperience@mazdausa.com

I just filled out my Mazda survey honestly and told them I wold have been better off purchasing a OBD-II reader and tablet than to spend the $349 to hav ethe car returned to me with "fresh" gas and the cat still "slightly" glowing on occasion.

Just install a race pipe keep your cat, re-install cat for emissions if you have to in your area. Dont get a resonated mid pipe or anything with packing, let your 8 breathe for once. Buy an extra read o2 sensor for when you do emissions. Dont keep the cat on.. my 8 blew a hole right through the center of the packing about the size of my fist..

I finally had a chance to monitor the cat temps today on my 14 mile - 45 min commute home. Here's the catalyst temps and coolant temps from ~ 30 % stop and go traffic and the rest spirited highway miles. See any issues in the Series II (S2) coolant temps or cat tempos on this average day?
https://cimg1.ibsrv.net/gimg/www.rx8...a0adbc39d6.png

IAT = 75 °F, 40% rh

https://cimg2.ibsrv.net/gimg/www.rx8...4cf2484657.png

IAT = 75 °F, 40% rh

I am guessing the stop and go was towards the end, around where you've spent $61,500 on your car :D: ?

Cat temps seem pretty typical to me.

Jastreb: Yes the last portion of the trip was stop and go traffic. I need to fix the macro that imports this specific data into my stats software (SAS) so that the date/time doesn't appear like I drive a Land Rover.

^ LOL at wannawankel thinking that owning an RX-8 is less expensive than owning a Land Rover.

Those temps look normal to me.

Thanks - just getting the car and monitoring ready for my trip to DGRR

Have you done a visual inspection on the cat yet?

I suspect those "cat temps" are more like exhaust gas temps, and so may not indicate a bad cat.

Also, are your STFT and LTFT's reasonable now?

Short Term and Long Term Fuel trims
 

I have and on occasion I can still see a faint glow coming from the top of the cat. I see this glow indirectly along the "ceiling" of the underbody. ST and LTFT are
https://cimg7.ibsrv.net/gimg/www.rx8...2c7571d2bb.jpg