I noticed when I was changing my oil today (5.4 Liter), that when I removed the filler cap, there was a white/grayish substance under the cap and around the opening of the filler tube (not a lot, but noticeable). The dipstick is clean, truck has 10,000 miles. Is this anything to be concerned about?

 

Probably what you're seeing is moisture. Some moisture content under the filler cap and around the filler neck is normal, especially if you make lots of in town trips with lots of stop and go driving.

 

Thanks Quintin, that makes sense...

 

This question comes up everytime the weather starts to cool down. It's normal, cardboard in front of the rad is my best friend where I live. Temps of -30 C are the norm 5 months of the year. Oh, can't forget the block heater....