Wouldn't have believed it....

yellowperil · 03-02-2010, 11:41 AM

Wouldn't have believed it if I hadn't done it myself, but changed over from Valvoline 15-40 to Mobile 1 15-50 thinking all that Syn Oil "will cause leaks" was just nonsense. I wanted to use a more modern oil (and the same as my wife's Mercedes). Well I had a totally dry (no leaks) engine, but sure enough my motor started leaking. Only slightly, but still it's a leak and very unwanted. I then re-read the oil bible, and it's quite a brain freezer for a non scientist, but decided to use Swepco 306 15-40. It seemed to be well recommended.

So I suppose hoping to see no more leaks is too much to ask, but will hope for the best. So.... seems like synthetic WILL indeed end up on your garage floor!

yellowperil · 03-02-2010, 11:43 AM

PS This was in my 86 3.2 by the way.

darrin · 03-02-2010, 11:58 AM

As a fellow '86 owner, wanted to throw out that I switched to synthetic after my 3.2's top end rebuild break-in was complete. So far, around 45k miles later, zero drips on my garage floor. I believe that fresh seals/gaskets are the key here.

Steve@Rennsport · 03-02-2010, 12:02 PM

Quote:

Originally Posted by darrin

As a fellow '86 owner, wanted to throw out that I switched to synthetic after my 3.2's top end rebuild break-in was complete. So far, around 45k miles later, zero drips on my garage floor. I believe that fresh seals/gaskets are the key here.

Absolutely right, Sir,....

yellowperil · 03-02-2010, 12:31 PM

So... Just so I understand. even though I had a total dry engine, ( I checked all the time) in order to use Synthetic I would have had to upgrade seals and gaskets?.

tvanbroekhoven · 03-02-2010, 01:01 PM

My SC has old gaskets. I filled her up with Castrol Edge Sport 10W60.

No leaks !

Dixie · Dixie's Garage

Keep in mind that modern oil and cars with flat tappet cams, like an old 911, do not get along. l'lI leave you to do a search if you wish to know more. There's a plethora of info on the forum regarding this topic.

darrin · 03-02-2010, 01:13 PM

Quote:

Originally Posted by yellowperil

So... Just so I understand. even though I had a total dry engine, ( I checked all the time) in order to use Synthetic I would have had to upgrade seals and gaskets?.

My recollection is that conventional oil causes seals to swell over time but that synthetic oil doesn't. Thus, switching to synthetic can cause the seals' swelling to dissipate and the potential oil leak that was otherwise contained by the previously swelled seal to turn into a puddle on your floor.

nesslar · 03-09-2010, 01:35 PM

Well....I had to dig this thread up, because I have been topping up with "old dinosaurs" of late (as in for months), as opposed to returning to synthetic (drained years ago) which was followed by "The Green Oil" for quite some while.....now, recently, no leak, though previously it wasn't very much at all. Hmmmm.......I do like it. '86 3.2.

dshepp806 · dshepp806's Garage

You are right Darren,...you can't blame the oil, at all. Get the seals and gaskets in order,..and you've a dry engine with synthetic............simple.

Doyle

yellowperil · 03-10-2010, 08:03 AM

As I said in my original post, this is what I know for sure. With 15/50 Mobile ! my '86 it would leak a few drops on my garage floor. Not a puddle, just a few drops (after a good warming up). So I changed to Swepco 15/40 a while back and after a good long drive to get operating temp there was no evidence of any leaks on the garage floor. Tried this twice so as to be sure. Both times the engine was up to full temp and it stayed dry. So,.. I'm not trying to start trouble but these are the facts in this particular instance. From here on in it's swepco for me! PS My engine has 99,000 miles and to my knowledge had no evidence of leaking until I used Synthetic oil.

nesslar · 03-10-2010, 08:28 AM

Exactly why I resurrected the thread, since my recent experience mirrors your's, though different brand oil, also 15W/40. The PO had Mobil 1 in it, I had switched to BP a couple+ years ago when I changed the oil. I can see that new seals and gaskets ought to fix ANY leak assuming the associated part/pieces are sound, but I am simply happy to have found that this has occurred, as I'm sure you are; beats tearing things apart! Like you (and the others I'm sure), no intention to be argumentative or anything of the sort, "just the (happy) facts". Though also an '86, my car has only 66K on it, with no record of "long" sitting/storage time....but difficult to say for sure.

86 911 Targa · 06:57 AM

Quote:

Originally Posted by yellowperil

Wouldn't have believed it if I hadn't done it myself, but changed over from Valvoline 15-40 to Mobile 1 15-50 thinking all that Syn Oil "will cause leaks" was just nonsense. I wanted to use a more modern oil (and the same as my wife's Mercedes). Well I had a totally dry (no leaks) engine, but sure enough my motor started leaking. Only slightly, but still it's a leak and very unwanted. I then re-read the oil bible, and it's quite a brain freezer for a non scientist, but decided to use Swepco 306 15-40. It seemed to be well recommended.

So I suppose hoping to see no more leaks is too much to ask, but will hope for the best. So.... seems like synthetic WILL indeed end up on your garage floor!

We have used Mobil 1 30, then 15-50 for decades on our '86, as in all of our cars.

Sure, we had leaks, from the breather tube (replaced), oil pressure sender gasket (replaced), one cam line (replaced).

However, with our front oil cooler fan thermostat set @ 210F (on), and 200F (off), we very rarely see temps over 210F.

Your decision should serve you well.

Good luck,

Gerry