synthetic oil in an old motor?

[GhettoPop]

Are there any negative effects of starting to use Mobil 1 Synthetic oil in my oil changes on my 130,000 mile stang? I dunno, it just doesnt seem like a good idea........what do you all think?

[bmxmon]

its all good, the only place that you dont want synthetic oil is in a new engine.

[Rev]

Originally Posted by bmxmon

its all good, the only place that you dont want synthetic oil is in a new engine.

I think Porsche, Corvette, and some others come from the factory with Mobil 1. Maybe they were broken in first with mineral oil, I don't know. What I do is use high quality mineral oil with a couple of changes for about 5,000 miles for the break in and then switch to Mobil 1. Not sure if that's really necessary, but that's the way I do it.

To address the original question, I think I would just stick with a good multi grade detergent mineral oil after 130,000 miles. I would use a little heavier grade like 10W50 maybe. At least that's what I do with my cars and it has worked well.

I do always use Mobil 1 now with new cars/engines after the 5000 mile break in. It does hurt a little buying 16 qts of Mobil 1 @ $4.50/qt. when oil change time comes for my 3 cars. Just think what it would be if I paid someone else to do it. And then there's the filters, sniff, sniff.

Rev

[grey88gt]

i swaped out my oil to Mobil 1 about a year ago when I got my car. It had 120,000 on it and now has about 130,000. No problems so far. The prior owener had changed the oil every 3000. It was a very clean engine internally when I got it and still is.

[USMC302]

I was always taught not to. Reason being, your seals are not leaking at the moment with the current oil and are "used to" that type and slickness of oil, switching to synthetic with high miles tends to "slip through" the seals because it's a slipperier oil. The non-synthetic oil is fine for you high mileage car if you have had no problems why switch now?

[USMC302]

Here is a story from a Mustanger from this very board.....

[QUOTE=88COBRA]Hey Guys, just some info and a story for you.

My car is a 1988 5.0 with 145,000KM. No oil leaks.

Everyone tells me to switch to Synthetic Fluid, so I try it. I get some Mobile 1 Synthetic 10W 30. I put it in and noticed an improvement right away. I drove it for a week, and I noticed leaks. I thought, nothing serious. BUT it was starting to go bad, Oil Pan, front seal, rear main seal, valve covers, ect.... It seems like every gasket went bad at the same time.

Now I am screwed! I have to pull the motor to get all the damn seals out. This is not a bad thing, but now I have to save every $$$ to do this. If I am going to pull it, I am going to do it right, 306 (maybe) valve job, cam, ect...

I have searched all over the net, and everywhere I go I read that Synthetic is the best, and will actually help stop oil leaks. Well it did the opposite for me. Luckily it is almost time for storage, which I will be doing this weekend.

[GhettoPop]

Originally Posted by USMC302

The non-synthetic oil is fine for you high mileage car if you have had no problems why switch now?

thats whats i'm thinking!

what is "good multi grade detergent mineral oil"? i'm guessing this is good old 10w-30? well, since the factory recommended 10w-30 which is still being used i will stick with it, i might bump it up to 10w-40, at least for the summer months...........the only leak i have is a valve cover leak, been there for years now......

on a side note, when i put in my tri-ax shifter on my t-5, i switch to Redline Synthetic ATF. i remember now that a month after i noticed fluid leaking from where the driveshaft enters the tranny, making a nice smokey drip on my x-pipe. i ended up replacing that seal (driveshaft seal?) anyway, was that a result of the synthetic switch?

[USMC302]

Originally Posted by GhettoPop

anyway, was that a result of the synthetic switch?

\

Makes sense.

[grey88gt]

Not trying to make ppl mad here but I have had none of those problems. But I do agree and it makes since of what you guys are saying. Guess I need to cross my fingers . Oh well engine and the tranys gona come out before long to paint car and freshen up everything. I had never run synthetic oil in anyhting till I bought this car, and all the other cars survied my abuse. Ill let yah know if starts ahh drippen. LOL

[flyin 5.8]

Changing to a synthetic can't "cause" leaks but, they can appear after the change. The better cleaners in the synthetics will clean the sludge from the inside of an engine revealing very small cracks in gaskets & seals. The smaller molecules of the synthetics also fit through these small cracks much easier.

I'm not a scientist but, this is the only explanation I've found for why some engins leak after the change and others are fine.