Under normal conditions, how long should the cat last? 05 with 36k miles. Ignition is and always has been healthy with the exception of battery drain due to after market alarm which has been disconnected. New plugs, wires and coils at 30k. It flooded 2x that I am aware of. Once with me and once with 1st owner. I premix 1/2 oz/gal. First owner did not. I redline 1 or 2 times per drive. The last few months I switched to no ethanol gas which has made a noticeable difference in performance.

 

Hard to predict, but 80k is not unreasonable. Depends on many factors including your driving routine. Short hops are worse than long drives.

 

Have you upgraded the starter? Flooding is bad for the cat. Also, do you premix? Things like this determine life of the stock cat which you want to keep in good shape. Unless you want to be a straight pipe hooligan like the rest of us.

 

Yes I premix but 1st owner did not. I've heard some say that premix shortens the cat life. Others have said if you stay at 1/2 oz per gal you should be ok. Yes I did upgrade the starter as well. I'm hoping my spirited driving and red lining keeps the cat from getting clogged.

 

P.S. My hooligan days are over. Its more like geezer days at this point. Although by my driving you would not know it. 😆😆😆

 

The best bolt-on (or bolt-off) mod for this car is a midpipe. It will trigger a cel without messing with the ecm. There is a way to trick the 02 sensor with stock ecm. I digress.
Seems like quite a bit of the issues I see here on the forums results from catalyst problems or are directly related.

 

Does anyone know if premixing is harmful as some have stated? Am I correct in believing my spirited driving and redlineing is better for the cat. I usually go on long drives with the car, especially twisting roads in the mountains.

 

The RX8 on it's own naturally premixes so it's already harmful to the cat. Adding 2 stroke to the gas just accelerates the wear further. Definitely was always the weak point of this car. If emissions weren't a thing, this engine would have been far more popular than it was.

 

2 stroke oil doesn't contaminate the cat unless you're burning massive amounts of it. Regular engine oil, by contrast, can, although modern oil standards have cut down on heavy metals which kill cats. The absolutely worst thing for the cat are floodings or frequent cold starts. Fuel-rich exhaust going into a cat that isn't up to effective temperature causes is the mechanism by which cats accumulate deposits and lose efficiency.

Cats definitely die, but I don't see how premixing is a factor in that. 99.9% of the combustion material in the engine is gasoline, not oil. The oil's contribution is meaningless.

 

It can over time do damage to the cat. This is why we recommend 4 oz if catted 8 oz if decatted.

 

I thought the recommendation was 1/2 oz per gal for catted?

 

Yup, 16 gal fuel tank that works out to 4 oz.

 

How? There is nothing in ashless oil byproducts that has any effect on the cat.
There are 2-stroke engines with cats

 

Cayman, your math is off. 1/2 oz per gal is 8 oz per16 gal.

 

Yep.