what high mileage oil do you guys recomend the most. i have a 99 f-150 with 191,XXX miles and looking for something to keep it running smooth for even longer, i have always ran a conventional oil and i was just wondering if i should switch to something different??

 

As much as I'd love to promote Amsoil, I'd have to say if you have already put this many successful miles on this truck then keep doing what you've been doing.

 

What "conventional" oil have you been running?

 

Bingo, the last thing you need is a oil with more detergents cleaning away the inside of the motor and now you develop leaks from various gaskets

 

YUP, don't go to another oil different than what you are already using.

May I ask what brand you are using?

Good Luck!

 

Mine has almost 150,000, and I run Castrol GTX 5w-30, I have no problems with it, and the truck runs smooth considered the way it is driven all the time.

 

Ive never seen any evidence to suggest that they are any benefits to be had with using a high-milage oil.
If you wanted to make a switch that would give you better fuel economy, Motorcraft 5w-30 would be a good choice. Its a synthetic blend, so it gives you some of the benefits of a synthetic but its not as expensive as a synthetic. I think it costs something like $2.50 a quart.
However, if you are having good luck with what you have been using, you could stick with it.
Ive got 173,000 miles on my truck with few problems (knock on wood). Most of those miles were ran on Mobil Drive Clean and Mobil Clean 5,000. I recently made the switch to Castrol GTX because it has the highest rating of any conventional oil, but I will likely make the switch either back to Mobil Clean 5,000 or to Motorcraft because of how expensive Castrol is.
Castrol is good stuff though.

 

I've used Valvoline since day 1 in my 2000 f150 .After 100,000 I started using Valovine High Mileage . Now, I'm at 208.500 miles. Needless to say ,I'm using Valvoline In my 06 as well.

 

I use castrol gtx high millage works good for me