So Just got a new screw, and I'm gonna change the oil. I have no idea what type of oil he had the truck changed with and he doesn't either(had all his work done by someone else). I've heard of problems with switching to full synthetic if that wasn't the type of oil they used, should I be worried? The truck has 90k miles on it.

 

I used to put pennzoil 5w30 in my old truck, then i switched to the synthetic blend 10w30 to motorcraft, and i never had any issues, and that old truck had 200k+ on it!

 

Don't be worried. If all the seals are in proper condition there is no issue switching between a conventional and "synthetic". I put synthetic in quotes because most marketed synthetics are actually Group III. Group III is just a highly refined dino oil. Most "synthetics" actually have the same amount of seal conditioners as high mileage oils and should help seals.
Are you extending your oil change interval or do conditions warrant the use of marketed synthetics?