Wondering why some engines produce a lot of carbon deposits inside exhaust pipe and other remain squeaky clean for 100K+ ml. For instance - all Toyota Tacoma's i've seen year 2005 + getting charcoal black exhaust tip within first several thousand miles while Tacoma year 2004 and below mostly looking very clean . Seem like new engines design run much richer and if so what adverse effect can be in term of vehicle performance ? My Taco year 2005 / 47K ml, none measurable oil consumption if any at all. OCI ~7K ml f00l synthetic gr.III mostly PP or Synpower. Always top tier gas. My exhaust pipe color appear to be jet black (dry carbon buildup) since the first 5K miles. Same goes for all other 05+ Tacos i've seen in a parking lot.