Synthetic to Conventional Oil

[INF3RN0666]

Originally Posted by Polygon

So, you're saying that your gaskets with 485,000Km busted and you're surprised? I'm surprised it lasted that long. Like I said, the oil didn't cause the leak, and ass old gasket did. Also, can you prove that the oil caused the leak? Nope, I'll bet you can't. Also, for your reference her are the cars I've switched to synthetic all with no leaks before and after:

1989 Chrysler LeBaron GTC TII: 142,000mi
1989 Chrysler LeBaron GTC TII: 88,000mi
1994 Eagle Vision TSi: 112,000mi
1998 Chrysler Sebring LXi: 74,000mi
1991 Dodge Stealth R/T TT: 86,000mi

You're right. I can't prove that the oil busted the gasket because the gasket can bust at any given time. But when a gasket busts after 200 Km of changing to synthetic, I would assume that it was the oil conversion. Besides, most people don't replace a gasket before it starts leaking because they're not enthusiasts like you. LIKE I SAID, it's not going to blow your engine, but it will cause a leak if the gaskets are weak. It may not happen on all cars, but it does happen on some. BTW, all the cars you're talking about, with the exception of the first one, don't have high mileage. My eagle vision ran without any need for gasket changes until 450000 Km (not even the head gasket). My impala's engine died at 350000 Km and the gaskets are still fine. My buick is at 200000 and the gaskets are in good condition. So the oldest car you've ever done a conversion on has mileage of 230000 Km. The gaskets in that should be OK. That's most likely why they didn't fail from the conversion. Don't talk about your personal experience and call it fact, just like I'm NOT saying that changing to synthetic will blow your gaskets.

[curtis73]

Originally Posted by caddydaddy

When I opened up a 1972 Cadillac 472 with 98,000 miles, the cylinders still had cross hatch pattern on them. I don't think breaking it in with synthetics would have made it wear less, or not break in properly!

I cracked open a 75 Caddy 500 with 223,000 on it and there were still crosshatches at the bottoms of the bore, and the ridge at the top wouldn't catch a fingernail. The caddy 425/472/500 family used super high-nickel blocks. Great for long term reliability, terrible for revs.

In all actuality, synthetic oil isn't really any "slipperier" than conventional. People ascribe qualities to it that don't really exist because its supposed to be superior. Oil is slippery, so they assume the expensive synthetic oil is slipperier. Its just not the case. GM shipped several hundred thousand corvettes (with and without roller cams) with Mobil1 in the crankcase and no break-in other than driving it off the assembly line to the shipping lot. I've toured the Bowling Green factory, and there isn't a break-in section. Many of the vettes we got at the dealer had 3 miles on them, which is about the distance from the factory to the old lot.

Oil is one of the most misunderstood parts of an automotive engine. I have to say that I've studied it for years and I still don't know as much as I'd like to... and half the stuff I do know for a fact there are a thousand old-school gearheads that scream at me for being a liar.

So... I'll leave the research up to the individual.

[Polygon]

Originally Posted by INF3RN0666

You're right. I can't prove that the oil busted the gasket because the gasket can bust at any given time. But when a gasket busts after 200 Km of changing to synthetic, I would assume that it was the oil conversion. Besides, most people don't replace a gasket before it starts leaking because they're not enthusiasts like you. LIKE I SAID, it's not going to blow your engine, but it will cause a leak if the gaskets are weak. It may not happen on all cars, but it does happen on some. BTW, all the cars you're talking about, with the exception of the first one, don't have high mileage. My eagle vision ran without any need for gasket changes until 450000 Km (not even the head gasket). My impala's engine died at 350000 Km and the gaskets are still fine. My buick is at 200000 and the gaskets are in good condition. So the oldest car you've ever done a conversion on has mileage of 230000 Km. The gaskets in that should be OK. That's most likely why they didn't fail from the conversion. Don't talk about your personal experience and call it fact, just like I'm NOT saying that changing to synthetic will blow your gaskets.

What I am trying to say is that the oil did not cause your gasket to burst. It was on it's way out. Like you said they can go at any time but they should be replaced after a certain mileage just like things like timing belts. I wouldn't go around just waiting for stuff to break before replacing them since they can cause other problems, more expensive ones and leaky valve cover gaskets can cause fires.

I'm not trying to pass my opinion off as fact. What I am trying to pass off as fact is that synthetic oil will NOT blow a seal or gasket. Perhaps it was coincidence. Perhaps the PCV wasn't working right. Maybe it was because your VC rubber seal was so damn old it was going to burst regardless. Chalk it up to coincidence. My current LeBaron's VC gasket started leaking shortly BEFORE changing to synthetic and it only had 87,000 miles on it.

So, take that for what it's worth.