I have just noticed my 1st signs of OC at 19k. I use Motul 300v 5W-40 due to how hot the oil temps get when you drive it hard and I was just below the L mark on the dipstick at oil change today. Taking her back in 1k to begin OC testing. Here we go again, went thru this with my 03 G35, but not until around 60k.