Ik i have heard that i shouldnt put in full synthetic oil if the engine has more than 100, 000 on it.

Why?

Is this an old wives tale from when synth was first being used?

my 5.2L has 152,000 KM's on it and i want to switch, but i dont was bad things to happen to my seals.

 

Wives tale, you can search for it. Its been discussed

 

Myth, myth?

Girl: Yeth?

(I couldn't resist)

 

i had to read that 5 times until i got it. lol

 

on this forum?

 

Yes, this forum. Also, glad I could make you laugh.

 

IIRC, original synth formulations caused seals to swell differently than petro-based oil, so switching did often cause leak problems. The solution was new synth oil reformulations and the leak problems went away.

But -always one of those- once I shifted the final drive of a motorcycle to synth and it started leading soon after. My opinion was seal failure, but dealer blamed it on me using synth gear oil and wouldn't do a warranty repair. Since I used mfg-labeled synth gear oil approved by the mfg for that final drive, the dealer got overruled and repair was covered. Despite that, I was left with a lingering worry about switching. My wife insists her motorcycle uses more oil when it has synth than petro stuff - I am not sure she's right, but she has been about some things .

When I put my 2 questionable examples up against opinions of oil engineers (incl one who is a personal friend) that switching is fine, that prolly means my examples are BS. I know that motorcycle dealer was full of BS about a lot of other stuff.

 

it's crap... I put in synth in my 2000 at 125k miles and never had a leak from it.

 

I switched at 128K and it is bone dry - no leaks.

 

Ya, synthetic oils do not cause leaks, poor worn out seals cause leaks. If you leak with a synthetic oil, it means that your seals were already bad, just not bad enough for conventional oil to leak through. It's actually the molecular properties of synthetics (molecule size and consistency) that allows it to leak through worn seals more easily then a conventional oil would. Ironically, it is those same properties that make synthetics superior to conventional oil to begin with.