Synthetic Oil Comment---Bad News??

[Heyspike]

I was reading my Covette Fever Mag last night when I read something a little disturbing. February 2003, page 33 ,photo #4. let me quote"It seems that cleanliness was an issue when they were assembled, and the combination of time, heat cycles, and SYNTHETIC OIL will all but gaurantee a leak" .
What's up with that? Do synthetic oils leak more than regular oils?
I just bought an 86 and changed the oil to Mobil 1. Was that a bad move? Your comments please...--John.

 

[vettl83]

I switched the ZR-1 and the 84 CF to synthetic oil two years ago with no problems. I believe the theory is that the synthetics have a better detergent quality and remove carbon build up from seals and gaskets, which may cause a leak. Should that take place the only solution I think is to replace the seal or gasket. I believe if you have a few miles on the clock they recommend using a non kerosine based engine flush first before switching to synthetic. Just my experience. 84 CF 91 ZR-1

 

[WhalePirot]

Synthetics tend to leak more because they are thinner.

They are also a 'narrower' range of product, so they tend not to sludge when the lighter aromatics burn off. I am not sure the detergent level is any higher than any quality oil, but the insides of the engine seem to stay cleaner. Perhaps the lower viscosity keeps the gunkies flowing to the filter better.

 

[Twin_Turbo]

It's not recommended to switch to synth. on a non rebuilt engine or one that has accumulated a reasonable amount of miles.

The leaks are caused by cheapo cork gaskets.Some quality gaskets will keep the engine leak free.

As for the synthetic, there are a couple of sorts. The cheapest is the reconstructed mineral oil with additives.

The pure synthetics come in the di-ester based oils and poly-ester.

The di-esters are the cheapest but since the oil is constructed of 1 sort of chain the complete structure of the oil will disintegrate when you hit the break down temperature.

The more expensive poly based oils are the ones to use in your engine (if you want to fork over the bucks, that stuff is not cheap)

The poly based oil has a selected range of chains (bonds) and when you hit the critical temperature only the weakest bonds (longest chains) will break down, leaving the majority of the oil intact.

This is only a simple representation, it's actually a bit more complicated (bring additives into the picture) but that should give an idea of how things work.

Marck

 

[Heyspike]

Well I thought I would be treating the Vette with top shelf stuff using Mobile 1. Your right it is not cheap. The car only has 51k original miles on it. So hopefully, I will not start seeing puddles of oil under it. Maybe there's not that much dirt inside yet.

 

[The Car Whisperer]

When I tried synthetic in my 86' it leaked oil. There were no oil leaks before the synthetic. I used it for 2 more oil change cycles and it still leaked, mostly around the front crank seal. I changed back to regular oil and the leaks stopped after a few oil changes. I'm sticking with the old fashioned stuff. I change oil and filter every 3000 mi so I don't see any significant gain in using oil that costs 3x the price of good quality regulay oil.

 

[Lucy64]

I have heard this is a problem with synthetic oil. Any minor leak will leak even more with synthetic. I have heard not to change to synthetic with older cars. How old...I don't know?? I have not changed and will not change on my 64. I have a 98 M3 BMW and have considered changing on that, but presently still run Castrol GTX oil.

 

[TomsToy]

If your talking about the C4, I don't think it's always the oil. The intake manifold is known to leak after some number of miles, particularly if the assembly plant didn't get all of the oil film off the surfaces, prior to putting on the sealer. I had the problem and resealed the intake and no problem afterwards. Several of my C4 buds have had the same problem of thier vettes "Marking it's terretory".

 

[The Car Whisperer]

All I can say from my experience is - Had no leaks before synthetic / had leaks after synthetic.

 

[LOUVETTE]

oil

I am running penzoil 5w 30 in my stock 89 with a ac delco oil filter
did have slick 50 in there also but to many bad comments about it so i just run the oil and change the filter 25 k miles. no synthetic here......owners manual doesnt say to run it............lou

 

[Twin_Turbo]

Synthetics are far superior to mineral oils, the properties can be taylored to exact specs, where the minderals are ballpark. I will never run mineral in any of my engines, synthetic means no sludge, clean engine. If you pull an engine that has run on synth apart you will instantly notice the difference.

Marck

 

[chuck]

Marck isn't Mobile 1 still a petroleum base? A true synthetic would be Red Line. Chuck

 

[Twin_Turbo]

It depends on what product line. I'm not sure, but it could very well be possible that the mobil1 is a reconstricted mineral oil.

I have shell Ultra Helix 10W60 (used in Ferrari challenge) and it's a true synthetic.

Marck

 

[qwall]

Re: oil

I am running penzoil 5w 30 in my stock 89 with a ac delco oil filter
did have slick 50 in there also but to many bad comments about it so i just run the oil and change the filter 25 k miles. no synthetic here......owners manual doesnt say to run it............lou

i'm pretty sure you meant 2,500 miles right?
as far as synthetic goes, like mentioned above, it you never udes it and your car has some miles on it, chances are engine will leak, synthetic keeps the engine cleaner and leaves less gunk.

q

 

[Heyspike]

Well I kind of knew this topic would create a good discussion, as far as the technical side of oil--it's all greek to me. It seems to be a matter of personel choice. I'll keep the Mobil 1 in there, and if I see any problems this spring or summer, maybe I'll change it back.
Was going to get her out again today, but it's nasty here. Snow and rain coming.....................John.

 

[Corvette-Pilot]

Synthetics tend to leak more because they are thinner.

This is something that has allawys bothered me??
Isn't a 10W30 a 10W30 regaurdless of it being natural vs Synthetic?

I thought the basic advantage to Synthetics is that they stay fluid to much lower temps and don't break down at higher temps.

I don't see how the same weight oil is any "slipperyer" either??

Just figured the flow rate at a given temp would be what it is regaurdless.

 

[Twin_Turbo]

The weights refer to the viscosity of the oil. The viscosity is dependant on the chain size of the components and on stuff like viscosity index improvers, they put that in oil to make sure it doesn't thin out too much.

low weight oils have a lot of vii, see it like this. 10W30 is a 0 weight oil that won't thin out more at high temps than a 30 w oil would (or the 10w oil will be as thin at high temp as the 30w would be)

The advantage to synthetics is they are less rpone to breaking down, this means they will keep adequate lubrication with a much thinner oil film than the minerals.

Mineral oils tend to have a lot of VII (especially the low weight, 5W30, 10W30) and VII don't lubricate, oil does.

The VII are coiled up polymers, coiled up they hardly influence the viscosity, when it gets hotter they coil out, long strads do influence viscosity.

Marck

 

[Vettelt193]

Twinnie gives a very good technical view... i will put in in lamens terms to possibly help a bit

Synthetic oil is man made, so they can make every particle of oil the same size, we will call this size X for our sake.

X is just the right size particle of oil, it is small, but not tiny, and not large... this allows for excellent consistancy and protection

Standard oils have a wide range of particle sizes, so, while there are some particles the same X in size, there are many more particles bigger than X, and a minor number smaller than X. Any particle Bigger than X won't protect as well, smaller won't either... there is also a problem with the lack of consistancy.

In synthetic: Since all the oil particles are X in size, if there is a path in any seal or gasket in the engine that an X size particle can get out, any particle of synthetic can work its way through, so you have a nice steady leak.

In standard oil: you may have a few smaller, but the few bigger particles may even act to 'plug the leak' or path out of the engine... so fewer leaks.

The L98 has common leaks with standard oil... with the LT1, those leaks were attemted to be fixed, but the addition of synthetic oil created new leaks...... When my corvette tech talks about the leaks, he refers to the engine as 'seaping oil' since it is just slowly seaping out of the engine.... I have had 3 C4's, my L98 leaked (standard oil), my LT1 did not (synthetic), and my LT4 currently leaks (synthetic).... I think at the end it comes to luck fo the draw... hope this helps

 

[Corvette-Pilot]

Clear as oil :crazy

 

[TomsToy]

LOL, Man! I thought a leak was just a "Leak". Never knew it was rocket science, but thanks for the info.