Last month I changed my oil with castrol edge w/ spt 5w-30 in my 2005 silverado w/ the 4.3 v6(i got it and a p1 filter at pepboys for 23 dollars). I have over 1200 miles on it so far. Well Today I checked my oil today and it looked like a dark golden brown color. When I checked the oil when I had QSUD 5w-30 (the previous oil that was in it) that had over 2000 miles, it looked a lighter color, kinda like almost new. I find this weird, but im wondering if castrol was meant for extended oci's. My truck only has little over 55,500 miles on it and I dont sense any sludge issues.