Hey guys I just bought my recently diseased paps truck with 139k. It's an 05 5.4. I don't think he ram synthetic in it but I have no way of telling now obviously. My question is, is it too late to switch to synthetic now? Especially if it's never had synthetic? And I'm thinking of going to 5w30 as I'm not sure what oil he used but my guess was what was required. Thanks!

 

Never too late for synthetic, 5w-20 is what it takes

 

Agree. Use Motorcraft 5w-20. And a Motorcraft FL-820S.

 

A buddy of mine told me that after 100,000 miles it's hurtful to switch to synthetic because it's thinner and will get into the broke down parts of the engine

 

Im not sure what 'broke down parts' hes referring to. But synthetic oil will clean your engine, and its possible that if you have an oil leak the synthetic will clean any deposits around and and cause it to leak worse. But it will not cause any problems if the engine is in good shape there are no worries. I've owned several vehicles that i bought with over 100k miles and always used synthetic and never any problems. Your buddy is just contributing to the myths of synthetic oil.
Also, synthetic is not thinner, oil weight is the same 5w-20 is 5w-20 whether its conventional or synthetic

 

Awesome thanks guys. I've been reading that 5w30 is causing guys to have less engine noise like the phasers. I haven't really had any problems with the phasers but I figured if it's quieting them down then it will delay mine even further.

 

I would run the recommended 5w-20. If you run different oils with a different viscosity it could improperly lubricate the engine and actually cause damage

 

I'm pretty sure that your truck came off the lot with semi synthetic 5w-20 so it should still be ran with synthetic but even if it isn't I don't think it would hurt it