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high mileage switch to synthetic = oil leak?

 
silver97z
I love my Chevy Chevette!
Posts: 4
Joined: 04/08
Posted: 04/12/08 09:21 AM

I recently purchased a '96 TA with 95,000 miles on it.  When I changed the oil I switched to synthetic and now have oil all over the place.  Small bit behind the crank on the front of the block, the block itself is wet.  The oil filter, drain plug, oil level sensor, and tranny are all covered in oil and it's been dripping from each of these as well. Shocked

I've read on cz28.com and heard from a couple of other sources that the sythetic oil has smaller molecules than the dino that was previously used and that it could leak where the dino would not have been able to.  I've also heard that the synthetic would clean the seals and allow it to leak around them until they seal back up? Confused

Anyone have any ideas?

Thanks, Brian  

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steveSSLT1
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Posts: 1
Joined: 04/08
Posted: 04/12/08 01:18 PM

I have a high mileage (^ SS Impala, same thing happened. About 125000 mi, switched to syn oil. Leaked from the rear main, oil pan plug, level sensor, etc. I have repaired a few (not the main) and switched back to a hiogh mileage oil. It has helped a little. My big problem is the oil dripping on the convertor. Smells bad when you stop at a light and park.  

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extanker
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Joined: 04/08
Posted: 04/12/08 03:31 PM

ive heard give it some time and the leaks stop but with high miles the seals are old and hard. good luck  

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insi10
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Joined: 07/09
Posted: 07/13/09 11:21 PM

My car is not a GM car, but a friend with an older Z28 had a similar experience. My experience: In January 2009 I took my Audi S4 to a private repair shop.  Sometime years ago, it had been switched from the synthetic oil it came with to non-synthetic oil.  

In January, there were NO oil leaks--not a drop.  The mechanic who replaced the timing belt and water pump in January decided without input from me to switch it back to synthetic.  Very bad move!  Within a couple of days, the left head gasket began leaking oil onto a hot exhaust manifold.  It was smoking visibly and delivering a bad smell into the car.  By the time I could no longer put up with it in May, it needed leaks repaired in FIVE places, including the seal behind the timing belt.  Oil had leaked onto the new timing belt, necessitating its replacement.  (So there was either leak there before the timing belt was replaced in January, or the mechanic missed it and it wasn't dripping -- an unlikely circumstance.  But it did begin leaking afterward. That strikes me as a very telling detail.)  

Repairs at the dealer in May came to $2,600 for all the leaks and the new timing belt.  Ouch!   I have subsequently done considerable research on the web about this phenomenon because I considered suing the garage.  Again -- it went from not a drop of oil seepage to leaks in five places including the very one at the place the mechanic replaced the timing chain.  That is a very dramatic and sudden change.

I have decided against suing because here is what I find on the web: in most cases, leaks don't happen from changing to synthetics on an old car.  But it does happen to some.  I could find no bulletins saying "Don't do it," and lots of arguments in favor of switching to synthetic.  So I see no reason to believe that the garage should have known that leaks would occur.  The repair shop was clearly pursuing what it perceived to be the best practice in using synthetic oil in my car.

So why does this happen only sometimes, not most of the time?

My theory: possibly certain patterns of driving (I drive fast), or certain combinations of former oil and synthetic oil, or possibly leaving the old oil in too long and getting sludge buildup that acts as a sealer (thereby delaying leaks that might have occurred earlier), or some other combination of events, causes this to happen in a few cars with the switch to synthetics in old age.   Until such time as I were learn differently, and that the garage should have known better, I'm taking the $2600 repair as my bad luck.  

But that is a lot of money to piss away for the small benefit of better oil.  My word to the cautious is: why risk it on an old car?  The old-fashioned oil got you this far.  Stick with what worked.  For a newer car, start synthetic and stay with  it.  

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LS1_TA
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Posts: 1
Joined: 07/09
Posted: 07/31/09 02:29 PM

i WOULD SWITCH BACK TO REGULAR AND CHANGE IT EVERY 3K.  
..

99 T/A SLP LID JETHOT LONGTUBES CUTOUT
TUNE

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RPM1
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Posts: 1
Joined: 08/09
Posted: 08/25/09 06:46 AM

Icon Quoteinsi10:
My car is not a GM car, but a friend with an older Z28 had a similar experience. My experience: In January 2009 I took my Audi S4 to a private repair shop.  Sometime years ago, it had been switched from the synthetic oil it came with to non-synthetic oil.  

In January, there were NO oil leaks--not a drop.  The mechanic who replaced the timing belt and water pump in January decided without input from me to switch it back to synthetic.  Very bad move!  Within a couple of days, the left head gasket began leaking oil onto a hot exhaust manifold.  It was smoking visibly and delivering a bad smell into the car.  By the time I could no longer put up with it in May, it needed leaks repaired in FIVE places, including the seal behind the timing belt.  Oil had leaked onto the new timing belt, necessitating its replacement.  (So there was either leak there before the timing belt was replaced in January, or the mechanic missed it and it wasn't dripping -- an unlikely circumstance.  But it did begin leaking afterward. That strikes me as a very telling detail.)  

Repairs at the dealer in May came to $2,600 for all the leaks and the new timing belt.  Ouch!   I have subsequently done considerable research on the web about this phenomenon because I considered suing the garage.  Again -- it went from not a drop of oil seepage to leaks in five places including the very one at the place the mechanic replaced the timing chain.  That is a very dramatic and sudden change.

I have decided against suing because here is what I find on the web: in most cases, leaks don't happen from changing to synthetics on an old car.  But it does happen to some.  I could find no bulletins saying "Don't do it," and lots of arguments in favor of switching to synthetic.  So I see no reason to believe that the garage should have known that leaks would occur.  The repair shop was clearly pursuing what it perceived to be the best practice in using synthetic oil in my car.

So why does this happen only sometimes, not most of the time?

My theory: possibly certain patterns of driving (I drive fast), or certain combinations of former oil and synthetic oil, or possibly leaving the old oil in too long and getting sludge buildup that acts as a sealer (thereby delaying leaks that might have occurred earlier), or some other combination of events, causes this to happen in a few cars with the switch to synthetics in old age.   Until such time as I were learn differently, and that the garage should have known better, I'm taking the $2600 repair as my bad luck.  

But that is a lot of money to piss away for the small benefit of better oil.  My word to the cautious is: why risk it on an old car?  The old-fashioned oil got you this far.  Stick with what worked.  For a newer car, start synthetic and stay with  it.


It's a shame that that synthetics behave in this manner. I sell synthetic oil and have just come across the leaking problem on a customers Tahoe with 170,000 miles on it. I also believe it's caused from the removal of deposits that act as a seal to hardened/ shrunk older seals. Now the customer needs to reseal oil pan. Looks like I will have to factor in mileage with choosing if a car is a good candidate. In the long run, I feel synthetic oils will benefit car owners in many other ways such as keeping expensive dealer repairs from happening in the first place. It's a shame that the car companies don't start the cars off right when they are built and install full synthetics through out entire driveline. Dino oil will go the way of points and bias ply tires soon.
In the mean time, perhaps sticking with regular oil on higher mileage cars might the way to go, just to be safe.  

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mpayne
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Posts: 258
Joined: 10/07
Posted: 08/25/09 09:38 AM

Strange stuff happening, I have 160k on my daily driver and use systhenic oil after I hit 150k miles and I haven't felt a difference or seen any leaks. I know my gramps always bugged my to switch saying you will get more mileage out of car but I don't see how changing to a better oil should kill a vehicle.  

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midiman1962
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Joined: 06/08
Posted: 09/11/09 03:43 PM

a little mineral spirits might swell those old seals for a few months...just a thought.  

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NuTiger
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Posts: 1
Joined: 10/09
Posted: 10/07/09 03:21 AM

You have 3 choices, go back to dino oil, replace all seals/gaskets, or just deal with the leaks till they seal up again. I had this problem with my 96 9C1 Caprice. It took almost a year before it stopped leaking. Just giving you a heads up.  

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97Firebird3800
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Posts: 2
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Posted: 10/22/09 08:43 PM

At 95,000 try using a fully synthetic high mileage oil. It will give you all of the benefits of a synthetic plus it has seal conditioners to help prevent high mileage leaks. The most likely cause is the fact that synthetic oil cleans your engine much better than the petroleum based oils. The simple fact is, you had bad seals and gaskets before the switch, it is just that all the crap built up on them was sealing it up. The synthetic cleaned the sludge off and now the preexisting leak is showing itself. If you want proof of this, cut open your oil filter right after your first run with synthetic and compare it to the same engine with petroleum oil in it. There will be way more crap in the filter with the synthetic than the petroleum. I did it as an experiment when I got my car, I bought it with 42,000 miles on it and immediately switched it to synthetic. I now have 122,000 miles and no leaks ever. Need even more proof, pull the valve covers before and after the switch. The difference is crazy.
Best thing that you can do at that mileage is pull the engine yourself and give it a once over. It could use a refresher at this point. LT1s are easy to rebuild 2. Summit Racing sells books on rebuilds and performance builds that take you through the whole process. With basic mechanical knowledge, a good machine shop and some friends, you should be able to do it in your garage. My buddy and I built a 383 LT1 for his 1993 Z28 when we were just starting high performance in tech school. Hope that this is of some help. Give it a try, it may be a pain in the ass, but you will have fun with it 2.  

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