Looking at buying this truck. 06 f150 100k 4x4 looking at the oil it's real black, old looking but kind of clumpy or gummy could this just be from lack of oil changes

 

Yep. I had the valve cover off of mine when I first got the truck and it was starting to sludge up. I used oil flush before every oil change and use synthetic oil and now the engine is spotless. I suspect the previous owner didnt change the oil as often as necessary.

 

I wouldn't buy a truck with oil like that unless the price was low enough to cover getting a new engine.

If you want to go ahead with it, I agree with SuzukiRider advising to flush the engine.

 

Walk away, unless you have a mechanical back ground.