Probably a dumb question(new Kubota owner) but here goes. I just noticed some blackish residue? on the loader arms on the exhaust side of the tractor. This residue will wipe off somewhat and comes off pretty easily with some soap and water. Tractor has about 30 hours and since it has no DPF it does smoke when starting as expected. Noticed it on a day I started it in the morning when the temp was below 30 although it probably was there and I hadn't noticed it before. Although it did smoke more that day, due to the cold temp, for a brief period of time. I assume this is normal? Not a big deal just a curiosity. Thanks for your time.