I know many swear by regular octane gas and I have used it in my old is250, but with the nxturbo I use premium...no idea on whether it will be important over 10 yrs Iusually own a vehicle...but its getting premium. I live at 5000+ft altitude and I discussed this on older threads...but altitude makes a difference...I bet I run leaner than those at sea level. and I still run rich....sigh

 

now that i think about it...its a safety precation as rich fuel doesnt shorten the life as a lean mixture will...so its about longevity unless someone wants to argue the point.

 

Every turbo car i have owned has had soot on the tail pipe. To reduce said soot, you need to drive the car aggressively every now and then, i found this helps to blast it out of there

 

Don't really care about soot in tailpipe. More about what was trapped by cat.

 

Most likely nothing, do you notice how rich and smelly the nx is on startup and the start sound it makes? This car does a great job at preheating the cats and once they are up to temperature they should be pulverizing most of anything that is in the cats. I bet a lot of that soot is from the warm up process, i'm sure adding an oil catch can would also minimize the soot. The egr system isn't doing any favors to the junk going into engine/out of exhaust either, but thats the price you pay for lower emissions.

 

Not really, but it can get stinky going uphill, that's for sure.
I understand what you say. I simply can't get over idea that soot, being unburnt particles, does not clog cat eventually. Especially for those who run short trips or never gas it on FWYs... the grandma drivers. Cats have to be brought to white hot to burn stuff out. And, to be honest - why? Engine should run clean to start with. Instead of justifying something.

 

I do get your point, there must be a reason for it. I know that in modern DI cars that are high compression, there is extra fuel dumped in to help cool the engine at certain times. This may be a factor in the soot. If you every look at a turbo car modified to run on e85 ethanol or race fuel, their tips are usually white and have a fine white soot on them. I've seen this in enough cars to believe that there must be a reason, my educated guess is the cooling with extra fuel, but I am not an engineer, at least not a certified one.

 

Well, whatever the reason - particulate is going through exhaust and cat.

 

Don't you think soot may be a product of cat "after burning" and not by-product that goes through cat to exhaust?

 

Maybe. I am not exhaust specialist. I only know that I had several Yotas with pipe crystal clear and now I have this. I am a simple minded person. Soot should not be anywhere around modern power trains.

 

My Audi A4 (gone now), with 2.0L turbo, had soot in tailpipe as well. So, I am not concerned, for now anyway.

 

OK, so I conferred with "the other side", folks that drive same cars but in a country where they do not really care if Lexus sells another O-ring in the US, so they are not biased.
Consensus is - it's not really good and is clear sign of at least initial air/fuel mixture being way too rich in petrol, resulting in unburnt particulate coming through can and out the tail pipe. Also, same explains rotten smell during start ups, as cat burns sulfur compounds. Or, they get stuck in cat and burnt out when cat gets real hot, what is my case. Mine does not stink during cold starts but sure does when gassed going uphill.
There was some chatter about Toyota not using advanced 2 chamber lambda sensors but I'd shelf this as just chatter.
That's basically answer to my question.