Originally Posted by cpllawncare
I have always heard not to switch from synth to conv but I did on my 05 F-150 am I in trouble?
You should be fine, tough I'm curious why you did that?
What happens when switching an old, or high mileage vehicle from conventional oil to synthetic oil is that the detergent in the synthetic oil will really clean up the inside of your engine and remove the sludge built up from using conventional oil. And sometimes, that sludge is the only thing preventing your seals from leaking.
In most cases, there won't be a leak, but it does happen.
In your case; you are going from a sludge free engine to using an oil which will create deposits over time. So you should be fine.