2008 ford 6.8 V10......bought this truck Sept 2016 with 155k, did a tune up including oil change went to do my next oil change and no oil on dipstick and a thick milky substance on my fill cap. I know ford's are good at drinking oil at higher mileage but this one has me stumped. Plenty of coolant in reservoir but never smelt oil burning or anything. Any advice ford a newbie to the v10?

 

You could have blow by, hows your air filter look? The milk on the oil cap is probably just condensate.

 

You have to check the oil level periodically between changes. You could simply have a PCV issue, or it could be something else. That issue gets kinda moot when the engine needs a rebuild because the proper oil level was not maintained.