A color change can come too if you just swapped brands but have been with the same one for a long time. Compare, say, Mobil 1 to RedLine. The Mobil and the RedLine will have different additive packages. One will protect differently then the other, one will also clean differently. If you have been with one and just switched, you could be cleaning something in the engine that wasnt cleaned before.
Originally posted by fasti4contour:
Well the oil loses it's viscosity and therefore will not coat the parts very well and yes contamination.But there really shouldn't be that much contamination unless the engine is getting fuel past the piston rings.But some yes is fine.sorry to sound anal but I love my contour to death and can't stand it when she doesn't run good 
The viscosity doesnt change that quick. My last change was pulled out at 6000 miles, the viscosity was still dead center at a 30w (210 degrees). The killer is the acids that the normal conbustion process creates. These deplete the bases in the oil. Thats what will wear out faster, the Royal Purple that I used last only had about 1500 miles of life in it.
The fuel/water that does get in the oil will vaporize under normal (read: fully warm) conditions).
If you are worried about it, send away for a oil sample kit. They will be able to tell you if all is good Clicky!
My Mobil 1 Test, if your curious. I have yet to upload my RP test. 
