I drained the primary fluid on my 2007 Heritage Softail Classice today since I was changing the derby cover and it was black. The last time I changed it was about 3000 miles ago with Spectro Primary Fluid and it went in clear. Is it normal for it to turn black with only 3000 miles of service since the interval in the manual is 10,000 miles? By the way, I used the Spectro Primary fluid again this time as well. Thanks.