This question it mainly directed to the guys with synthetic oil in their trucks. My F-250 has got 139K miles on it and has used conventional oil all it's life, the question is will i be ok to switch it to synthetic now? Or would be best to stick with conventional since it has some miles on it? I have been told that it has too many miles on it to make the switch. Also the same question applies to the tranny, yet it only has 65K since it was rebuilt, yet has gotten "warm" on one occasion the temps spiked at 200-220 and she kinda shifted funny when she was that hot.(needless to say a better tranny cooler is on the short list of things to get)

 

with that many miles on it i would just keep using the conventional. i switched one from conventional to synthetic at 15k miles and had no problems, but switched one at about 80k and it leaked like a sieve. anywhere oil could have leaked from it did.

 

I would switch both to synthetic.
The trans would run alot cooler on synthetic.
I have a '95 that I just got, w/138,000 on it, I'm switching trans, engine, & rear end over to full synthetic.

 

I just switched mine over to synthetic a little over a month ago. The Powerstroke has 293000 miles on it. It starts a little better on cold mornings, mileage went up slightly and no leaks.

 

Synthetic oil in everything I own.
My diesels are easier to start, runs quieter when cold and runs smoother.
Your trans will not run cooler with syn oils but it will take much more heat w/o the additives breaking down.

I switched to synthetics on quite a few older engines/trans and only had one leak. It was going to leak soon anyway. The thinner oil (syn) just makes it show sooner.

 

I've got full synthetic in both trucks in my signature, engines, trannys, and differentials. The 97 had 116,000 when I bought it, The 02 had 80,000 on it. No problems at all. Transgo kits are in both trannys, and a big tranny cooler is in the work truck, (the 97).

 

Your trans will run cooler with synthetic in it.

 

Just picked up my 97 with 145k and switched to synthetic, no problems..

 

another question, if i switch to synthetic and it does leak, what do i do form there?

 

synthetic doesnt make it leak you already have the leaks if it leaks the syn oil is just thinner and will seep through the leaks you already have better

 

I switched to syn at 90K, no problems

 

synthetic oil in the winter, conventional in the summer, I'm a some what of a cheap *** with 223,000kms on the engine and the only oil leaks i've dealt with on the engine is those stupid oil gallery plugs in the cylinder head. Curse those plugs, curse them.

 

I run synthetic trans fluid, and use Rotella Synthetic in the motor. Runs smoother and starts easier. 163k

 

Syn fluids all the way!!!
You cannot beat it.
Its vis stable at high and low temps.

Bill

 

i did something stupid based on a suggestion from dad. i bought my truck and it had always had synthetice for 145,000 miles. i switched it over to CONVENTIONALm but have had no motor probs in 60,000 miles