I'm looking to switch to a synthetic motor oil like Mobil 1 in my '89 Fox but a friend told me if I switch from regular motor oil to synthetic in a car as old as mine that it would deteriorate the gaskets and cause leaks. Is there any truth to this or is it another urban legend?

 

Ive heard that a bunch of times but dont know if theres any truth to it

 

Yea man switching to regular would be the most wise descision if you want ur car to last. I understand that is top of the line oil. But the oil is made for cars of certain requirements. You should defintaley switch to regular. These vw's last forever.

Dustin

 

I would not use synthetic in a car this old. You will burn more oil, and probably cause some leaks. I am working on a jeep right now that was switched to synthetic @165k it now has 171Kand has a few leaks that just started. Synthetics are wonderful on new or freshly rebuilt engines.

 

I sold industrial lubricants for a number of years... The above statements are partially bunk.
In older engines that were ran on dino oil, you have a fairly thick layer of varnish like buildup. This constitutes a seal, much like painting old leaky windows shut.
Synthetic is much more stable, and doesn't varnish. Synthetics typically have higher detergent levels that clean the crap out of your engine when you drive. The old dry seals that should have been replaced years ago no longer have the varnish keeping fluids from leaking. In many cases, after a few thousand miles the leaks disappear, in others the seals may actually fail completely.

Synthetics overall are best for preventing wear and damage to occur. On the other hand, they will clean the hell out of your engine and can dislodge massive amounts of deposits and varnish. You should drive no more than 1000 miles after switching before you change both oil and filter.

Also, take engine oil samples to a Catipillar or Cummins repair shop for oil analysis. They can tell you EXACTLY what's going on in your engine long before the symptoms manifest themselves... (trace amounts of coolant, or gas in your oil that you can't see or smell- early detection can save you a rebuild) also depending on the wear metals present in the oil you can know which bearings are wearing, or if your valve seats, rings, etc may need attention....

The short answer is that synthetics are the best for protection, but you may have to deal with issues that your sludge and varnish have masked.

Good luck!

 

i would stick with what ever it came with but i would never use synyheci in a car 20 yars old

 

No doubt synthetic lubes are a good product, However, I wouldn't use it in a car that old, and the engine was designed for
straight 30w hd oil, 40w in the South west. As a life long auto
truck,and tractor Tech , i've seen a lot of crazy things going on
with lubricants. A new vehicle started out on synthetic will work
just fine, but it still has to be changed when it's dirty. You will not
have a varnish build up with regular oil if it's been changed
properly. I have a diesel farm tractor that's 21 years old, and all
that's been used in it is Chevron Delo 400 30w. changed just
as it started to turn colors. After all those years I sold the tractor
to a guy that just thought it should be rebuilt, after the tare down
the engine was so clean and varnish free it looked new, and the
seals were not leaking or in bad shape. The engine did not need
the over haul. Oh.....the oil change on the tractor was twice a year.

 

Quality oil, and filters. Don't use Super Tech, or Fram filters. Valvolene, Castrol, Pennzoil...

 

Who learned you how to spoke? I did not read every bloody post on here...

 

I never learned to read. Use synthetic or die!