We have a 2008 Cadillac 3.6L direct injection CTS4 with about 53,000 miles. We bought it used and have put about 7,000 miles on it. It runs fine and I use middle grade fuel and assume the Cadillac dealership used Mobil One 5-30 synthetic oil if it was changed, (I don’t know if it was). The oil level dropped enough for me to add a qt of Mobile One recently. I read the blogs on oil consumption and it seems reasonable. However, I notice a lot of carbon in the tail exhaust extensions. I have cleaned it off with chrome cleaner but it comes back in no time. Is this a problem or a normal event for this engine series?
As long as the cars is running well and has been properly maintained, you need not worry about a bit of carbon buildup in the tailpipe. It’s normal. Keep it tuned up and serviced, monitor your fluid levels, and sleep soundly.
Probably you have emissions testing, look at the numbers. It could be burning oil or fouled injectors, bad plugs, wires etc. I would not call this normal. In fact when buying used cars I routinely check for carbon build up and pass on cars that have it. The biggest long term concern would be a catalytic converter in the future. It may go no for years, but anything building up so quicky would be a concern to me. Just for kicks I did the finger exhaust dip your finger in test on an 03 Chevy I bought 5 years and 70k mikes ago. Clear at 80k, slightest dusting of black on my finger at 147k.
I’ve noticed a lot more black tailpipes. It used to be (pre-cat converter) that you could tell if you were running not too rich by looking for light-colored tailpipes. That was probably from the lead product deposits. These days I wouldn’t worry about it, except if you are using too much oil. Keep track of it, see how many miles you go between adding a quart. You want that to be 1000 miles minimum, prefer over 2000 miles/quart.
Thanks for the feedback. I appreciate the comments. I will watch the oil level more closely and keep cleaning out the pipes.