HEY SCOTTY i have a 2011 lexus is250 with 144000 miles has alot of black soot inside the exhaust tip my oil and coolant levels havent changed and i have no check engine codes any idea what it could be thanks
Running rich. If you were burning oil it would be greasy, not "soot"
Some carbon buildup is normal inside the exhaust tip. Burning gasoline is dirty, and it's almost never 100% burned. My '99 Ford Ranger has 274k on it, for example, the fuel trims oscillate between +/- 3%, which isn't bad for the age, and the cats are 99.2% efficient. The 0.8% inefficiency is unburned hydrocarbons that can produce soot. It does have some very light sooting in the tailpipe. When you start getting a lot of build-up, like charcoal dust, you're running too rich. Sometimes you'll blow black smoke if it's really bad. Your CEL will illuminate long before that happens. Plug in a scan tool with live data and look at your fuel trims. If they read negative, the computer is subtracting fuel and you're running rich. A clogged air filter, dirty MAF sensor or dirty fuel injectors can cause it.
Put a bottle of injector cleaner in it and give it the Italian Tune Up. It'll probably clean out the injectors.
i saw somewhere that a really dirty air filter could do that, cause it to run rich
I have the same issue with my 2010 with 143k miles and it doesn’t burn oil so it probably is running rich.
Is your gas mileage affected?
Not at all. I consistently average 30 mpg in combined city/highway driving. I wonder if maybe it was caused by an issue in the past that was fixed but they just never cleaned out the tips.