Ford Repair: Motor Oil, castrol gtx, oil additives

Question
Would you recommend switching to synthetic oil in either vehicle or both
vehicles? If not what brand of conventional oil would you recommend
Pennzoil, Valvoline, Mobil 5000, Castrol GTX? Also should i use the high
mileage oil or a synthetic blend or standard oil?

Thanks

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Followup To
Question -
Is Mobil 1 a synthetic? I ahve been using regular
oil in both vehicles.
Answer -
Kenneth-

  Yes, Mobil 1 is a full synthetic.  I've found that synthetics, for the most part, provide better protection and resist breakdown better especially in tougher duty conditions.  Other brands like Royal Purple or Amsoil are probably better (Amsoil being the best I've ever seen), but both are much more expensive and can be very hard to come by.  You can switch out regular SAE oil for synthetic, no problem.  Just make sure when you change the oil you let it drain as long as possible.  By your second oil change it should all be gone (the old SAE oil, that is).  Hope this helps.

Steve

Answer
Kenneth-

  Yeah, I'd recommend it in both vehicles.  If you do decide on a conventional oil, however, absolutely DO NOT use Pennzoil.  A lot of Fords have problems with that oil for some reason.  I've seen a lot of clogged oil screens due to Pennzoil.  That "high mileage" oil is a bit of a gimmick to me.  I suppose it might work like it says, but even if it does it's just a band-aid.  If my motor has problems, I'd rather know right away and not have some oil additives cover them up until it gets worse.  So I'd just stick with the normal synthetic.  Hope this helps.

Steve