Well I am new to sites like this, just joined, have been spying for about two weeks since I bought an 04 Xterra. Think I got a very good deal,only had 18.5k,. The dealer I bought it from had a oil change sticker on the windshield like you see from Jiffy lube, indicating they had just changed the oil. I decided it was time to go synthetic from what I have been reading on here. Never used syn. before. Anyway the oil I drained out was Black as tar, definetly overdue and Not changed. Since I put the syn. in the engine is running much smoother, it wasnt skipping just vibrating kind of more than I thought it should. Now very smooth. I didnt know oil would do that. I am a tad worried about the nasty oil that was in there but I know those engines are tough and it will be alright. A dirty trick for the dealership to pull. Any similar experiences. Thanks., Hoop