I have an 86 5.0 (obviously) and i have about 74,xxx miles. I bought her back in december to fix up and use as my DD. I already changed the oil once with castrol gtx conventional oil but there was a sale at a local store on mobil 1 and an oil filter. I bought the mobil 1 high mileage fully synthetic oil because i read it has seal conditioners in it so it won't break any seals, and i bought just a FRAM racing HP4 filter. Since my motor is from 86 and is all original and stock, I'm curious to know if switching to this fully synthetic will be ok. So if anyone has experience with all this, I would much appreciate your help. So far all i've done was change my rear shocks/ quad shocks (bitch and a half to unbolt). but please help me with the oil if you can! I dont't want to make a bad mistake...