I always read that synthetic does not cause leaks.But in the early 90's I had three new cars.A 92 Lumina van,a 91 dodge spirit rt turbo and a 91 mitsubishi mirage.At 3,000 miles I started using synthetic in all of them and by 12,000 miles I had major leak problems in all of them.Had to get many different seals and gaskets replaced under warranty.I have used dino or semi-syn in all my cars after this and have not had leak problems.I would like to try synthetic again but I am afraid to.Did I have 3 lemon cars?or are synthetics different with seal swell then 10-15 years ago?
synthetic and leaks
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I am scared of that too. My wifes 2004 Mazda MPV is going on 12,000 miles and still no leaks on Mobil 1 my truck has 41,000 miles on it and is a 2000 and it has Mobil 1 in it right now with no problem but I will be trying Coastal 10w30 Full Synthetic and Supertech 10w30 HM with seal conditioners this next weekend.
Since the early 1990's BOTH the synthetic oils and gasket materials have improved greatly. This is much less of a problem than it was. On occasion you will get a leak off a vehicle that was run on dino and has some brittle gaskets when you switch it to synthetic. Then again the gasket probably weeps a little anyway with dino. I recently switched a 1991 Oldsmobile to M1 with no problems.
Also while the newer HM oil advertise that they contain "seal swell conditioners" so do modern day synthetics. To what extent? I do not know.
Also while the newer HM oil advertise that they contain "seal swell conditioners" so do modern day synthetics. To what extent? I do not know.
May also depend on the kind of synthetic and the seal material. I used Mobil 1, Amsoil, or Delvac 1 in my Saturn for many tens of thousands of miles with no trouble. One experiment with Redline and my rear main started leaking like crazy. Nothing has helped, including multiple Auto-RX runs, Max Life, and switching back to Mobil 1. Everyone will tell you (as they did me) that the leaks had nothing to do with Redline, that it was a coincidence, that the seals were marginal anyway and Redline simply uncovered a fault, blah, blah, blah. The bottom line? A fault isn't a fault until it's uncovered. I blame Redline.
Every situation is different. There is and always was a chance that syntehtics could cause a problem with leakage. However, one's odds are much better in 2005 than they were in 1990 of not starting a leak IMO.
do you think GIII synthetics are less of a leak risk than PAOs?
I wonder if non-synthetic gear lube would have done the same thing, or did it actually start leaking as soon as the synthetic was installed?
I have had Group III synthetic and a bit of Redline mixed in for 5000 miles in the '92 Aerostar with over 100,000 miles. No leaks yet.
Ran Group III and a bit of Redline in a 120,000 mile engine for 4200 miles and no leaks. And that one had seeps, but they did not worsen. Of course that one also had recently been AutoRx'ed.
I put Valvoline synthetic gear lube in two rear ends (65,000 mile and a 100,000 mile unit) and no leaks. Put Redline in a 70,000 mile rear end and no leaks, but the axle seals were replaced at the same time.
Now the power steering had seeps and I put Redline in it and the seeps got worse to where they now mark the floor.
Nice try! I don't think the lube is at fault on that one.
I first started synthetic years ago when my car had about 80k on it. It did already have a rear main seal leak but I didn't notice it getting any worse. Since then, the seal was replace and I haven't had any unusual leak/consumption problems.
'94 GMC V-6 in our boat. Mobil 1 15w-50 for 11 years. No leaks.
If any low milage car develops leaks with synthetic that means that the OEM used the cheapest low grade junk gasketmaterial available on the earth! I have never had a gasket leak due to the oil used and I have been useing synthetic since about the late 1980's!
If a high milage vechiles develops leaks shortly after switching to synthetic that means that the seal was brittle and dry roted from over extended OCI's with dino oil!
If a high milage vechiles develops leaks shortly after switching to synthetic that means that the seal was brittle and dry roted from over extended OCI's with dino oil!
The opinion seems to be that Group III base oils have a similar seal hardening/shrinking effect. Most Group III "synthetics" contain esters to balance seal swell.
I know it's not supposed to, but my observations in the shop are that synthetics can indeed cause seepage, leaks, and squished out gaskets.
Seems to be much less, now, but for sure in the past there was a 10-20% chance of leakage.
Factory gaskets and seals are very good now.
Seems to be much less, now, but for sure in the past there was a 10-20% chance of leakage.
Factory gaskets and seals are very good now.
Used Mobil One gear oil in my 89
Mazda P/U rear end.It took about nine years to seep out.Had to replace seals or it would seep on to the
brake shoes.It's not worth it.
Mazda P/U rear end.It took about nine years to seep out.Had to replace seals or it would seep on to the
brake shoes.It's not worth it.
And I've had windows in my house my whole life and never had to replace one because of a rock being thrown through it. So what? No offense, but your experience means poo-poo to me if my experience is the opposite. Maybe if you and I shared cars, that would means something to me, but otherwise you're just giving us your opinion about why your gaskets never leaked. Based on what you just said about high-mileage cars, you could just as easily conclude that your cars have simply built up all sorts of "false seals" that your synthetic oil won't clean out. See? Anyone can do it. Besides all that, regardless of what state the seals were in, if I hadn't switched to Redline (I believe -- that's my opinion), they wouldn't have leaked or wouldn't have leaked as badly. Don't really care if they were "brittle" or "dry-rotted." (Never mind that, as I stated, I'd been using synthetic from day one, just not Redline.) As I said before, a problem isn't a problem, practically speaking, until it's uncovered and changes functionally. Another example: Don't care if my radiator is old and marginal if it cools my car to spec. Could drive thousands and thousands of miles like that with no problem. If I put in an additive that gums up some of the passages so that my radiator stops working -- even if in a new, fully functioning radiator it wouldn't have made a difference -- guess what broke my radiator? The additive. That's just the way real life is. (Of course, who's fault is it for trying the additive? That's another question.)
Might depend on the situation. My old 305 leaked a considerable bit of M1, but with Syntec it was as bone-dry as it was with any dino oil. Go figure.
My experience agrees with mechtech's and kev99sl's. Sometimes things leak with synthetics when they don't with dino whether they should or not. My '91 Subaru is that way with its gearbox.
As to whether the primary base stock makes a difference (GIII vs. GIV vs. GV), the info here on BITOG says it should not. However, a fully-formulated oil contains many other ingredients so I would think that such a blanket statement does not quite apply.
As to whether the primary base stock makes a difference (GIII vs. GIV vs. GV), the info here on BITOG says it should not. However, a fully-formulated oil contains many other ingredients so I would think that such a blanket statement does not quite apply.
It's been my experience that introducing an older or high mileage engine to full or blended synthetic can cause leaks, even with the supposedly "better" modern day formulations.
I don't run synthetic unless I have an engine with less than 20k on it or I personally rebuilt the motor.
I don't run synthetic unless I have an engine with less than 20k on it or I personally rebuilt the motor.
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