Indiancreek

The leaks you have were coming sooner or later. seals wear and they leak in time. The benefits of the synthetic out weigh the cost of fixing the leak.
All the additive stuff is putting off the issue. I'd fix the leaking gaskets and seal and it will be done the correct way.
I build engines everyday. Take them apart on a weekly basis. There is a definate differance in the engine bearings of an older engine that has been on synthetic.
This year I have taken two apart with over 150,000 and have been on synthetic most of the. The mains were still as grey as they were from the start, and when mic'ed show very little wear. Both had good oil pressure just came out for a fresh engine during restoration.
I don't like it during break in, but generally switch over in the 10,000 to 20,000 range.
The two piece rear main, if installed correctly have no problem with synthetic. Most of the time I see the leaks from the valve covers, more often than not from shrinking cork gaskets. Sometimes tightening the bolts can end the leak for a time.
Parts that wear and seal fluids will leak in time.IMHO

peterek

So 10W-40 or 15W-40? any oil filter recomendation?

jb78L-82

OMG-Excellent comments!!!

If the leaks bother you or are too large to tolerate, replace the leaking gaskets-They were bound to start leaking sooner or later. All cars from this era leaked oil, sooner or later, with age and mileage and synthetics did not exist back then so blaming the synthetics is pointless!

I tolerate a few minor leaks with synthetic oil since I believe in the superior wear protection^(please see comments above from an engine builder which I am not).

Forget Shell Rotella-it's a diesel oil and DOES NOT have an adequate amount of ZDDP for flat tappet cam engines any longer. This fact is well documented. there are a number of commercially available oils, synthetic and conventional, with the correct amount of ZDDP (please see sticky at the beginning of this forum)

turtlevette

1. I can't believe people are still using cork gaskets. I know modern rubber/silicon based gaskets are at least available for the valve covers. Would be surprised if they are not available for the oil pan.

2. There's a reason for the change to a one piece rear main seal. The 2 piece is less reliable.

3. I don't understand why people are so opposed to additives that make seals swell. Its a simple and effective answer for older engines. What do you think "high mileage" oil contains.

4. If you are so **** that a few drops of oil bothers you, it may be a problem for you to own a C3. You will eventually break down under the stress of making an old car perfect and will wind up spending $150 an hour for psychiatric help. Throw an absorbent pad under the car and get on with life.

I bet if you throw on a couple of these, life will be good for you again.

http://www.jegs.com/i/Mr.+Gasket/720/585G/10002/-1

Remember to flatten out the part of the valve cover right around the holes on a steel cover. They get pulled in over the years from overtightening.

jb78L-82

:

peterek

So I changed the oil to 10W-40 and got Fram Ultra Tough filter,
but When i drained old oil ( 2-3 weeks old, driven 30 miles) it was really dark,
Should that be a case? nice clear oil turning really dark after 30 miles???

73StreetRace

Perfectly normal if previous oils were dyno and the new one is synthetic.
Acted as an engine cleaner.

wheatpj

I started using Mobil 1 15W-50 in my 71 LS5 last year after hearing that Rotella had been reformulated. It leaks at the main bearing seal same as with the Rotella. It might be my imagination but the engine seems to run stronger and less valvetain noise with the Mobil 1

78 C3 Light Corvette Blue

Common, Started using Synthetic 2nd oil change. Bought my car with 52000 miles on it. Previous 2 owners always had used conventional oil. 2nd oilchange went with Valvoline Synpower 10/30. Oil leaked from valve covers. Replaced no problem. Slight leak from pan gasket which after 30 + years was showing wear. Replaced no problem. Synthetic is thinner. By the way, folks will tell you not to use this oil. Hog wash. Valvoline recommends it and so does GM. Valvoline synthetics are still crude mineral base. Still true synthetic. Won't schock your motor and you can go back to conventioal at any time. Per Valvoline.

wheatpj

Just a side note, most of the guys on the forum aren't too high on Fram Oil Filters. I ran a Fram Filter last year but changed to Wix this year based on Forum recommendations.

Good luck with your new vette...happy motoring

jackson

Non-synthetic Shell ROTELLA T 15W-40 continues to provide good protection for C3 motors.

Now too often referenced; "the sticky" is fraught with unsubstantiated claims, personal bias & VOA test results sharing gross disagreement/inconsistency. I recognize the initial intent of OP & primary proponents of "the sticky" was likely to ONLY provide helpful info but I also see how the thread morphed into something less. Fact is, their own VOA numbers jumped up and bit em. Sadly, some of em just don't want to believe that truth. So, even though much $, time, speculation & personal pride went into "the sticky", its conclusions based on VOA are not credible.

Also, in 3 or more identical instances in "the sticky", I was misquoted in what I believe was an effort to discredit my arguments in favor of diesel truck oils. Once may be an understandable oversight but thrice is intentional, malicious fraud. I did not say anything at the time because creative editing was routine in that thread. I did not want my oil comments to become shrouded by a secondary pizzing match about poor character. Now, the thread appears locked; I trust no one will go back into it and change/edit what I point to here. Although the OP did Not execute the misquotes, I believe OP's personal bias allowed it to stand. In other matters, the OP made it amply clear how he held ultimate responsibility for his thread. Gross bias hurts credibility.

Now, I know the Rotella/similar Non-syn diesel truck oil continues to work good for me and lotsa regional flat tappet circletrack racers. They're reasonably priced & widely available.

By the same token, I have no good reason to doubt those synthetics & boutique oils often touted in "the sticky" are good oils & give their advocates good results also.

good day; I'm switching channels to humor & wisdom: click & clack's car talk.

jb78L-82

OMG-Enough with Shell Rotella! It does not have the correct amount of ZDDP-1,200 PPM. There is no documentation anywhere, especially from Shell that claims that Rotella has the correct amount of ZDDP for flat tappet cammed engines-none! Any oil will work in your engine, conventional or synthetic. Most people want to use an oil that provides the BEST protection from friction and wear, and is appropriate these last few years to minimize valve train wear.

OEM Auto manufacturers of high performance engines/cars almost universally fill their engines from the factory with synthetics-this is not rocket science-there is a reason, mainly they feel synthetics provide superior protection over a longer time-period.

If you want to use conventional oil, of course, by all means do so but this constant churn about conventional oils being as good as synthetics is tiring and quite boring at this point in motor oil life cycle since synthetics are well known to be superior.

Lastly, just to set the record straight again about what is a "true synthetic" versus the highly refined mineral based oils that are allowed to be called "synthetic" in the USA. Only in the US, after a legal challenge that our beloved courts allowed to be upheld, were oil companies permitted in the US only to call Group III mineral based oils "synthetic". Group III highly refined mineral based conventional oils are NOT permitted to be called synthetic in Europe and most of the rest of the world.

The following are Group III conventional oils that are highly refined in the USA:

Valvoline, Castrol Syntec (not Edge), Shell.

A true synthetic is a Group IV PAO ester that is chemically formulated so that all the molecules are exactly the same size, which is the real reason for synthetics' superior protection from friction and is man made.

The following are true Group IV synthetcis:

Royal Purple, Amsoil, Mobil 1, Castrol Edge

69vettester

I started up my new engine build with dino break in oil, in order to flush the special additives I had put on the cylinder walls ,cam lobes and rocker tip for the valve stem.
I ran the engine until hot, then changed to dino 10/40 for 500 miles, then put in the mobil 1 full synthetic.
Ill run full synthetic for the rest of the engines life or until they come up with something proven Better.

BAMvette

I'm in basically the same situation as you are. We purchased the '81 about 2 months ago, and the previous owner had synthetic in it.

It has a couple of minor oil leaks that sound about like yours. And the general consensus that Chevy small blocks of this era tend to leak a bit of oil is correct, IMHO. Drive it, monitor it, but I don't think you need to check it every day. Maybe once a week until you're comfortable.

Rather than go to all of the work of changing all the gaskets, I had decided yesterday that this morning I'm gonna change the oil back to Dino and run it from here on out to see whether it might help. Easy to do, and can't hurt. LOTS less work than swapping all the gaskets.

My choice for oil is Castrol High Mileage 10-40, with a Purolator "Pure One" filter.

It's got Mobil 1 5w-30 syn. in it now. No idea why he did that.

Car has 138K miles on it.

Nice to find this thread this morning. Was looking to see if I could find a thread that would tell me if the drain plug uses a disposable crush washer.

Anyone know?

Thanks!

billla

FWIW, although I agree that the VOAs have raised some valid questions the info at the top of the sticky regarding is 100% valid. The intent was always to lay out information and let folks make their own decisions - as noted in the sticky. If you don't like the VOAs, look at the MSDS where available.

I have information I can't add as the thread has been locked (and will soon be deleted) due to the actions of another user...but overall 1000-1200 PPM ZDDP is the minimum - as noted by cam manufacturers such as CompCams.

No bias, no nothing - just good information that everyone needs to evaluate. It's your car - make your own decision

Gaolei

My company builds oil purifiers for large machines, gas turbines and large compressors. This information is absolutely correct.

I once asked a friend who works for Lubrizol about which oil he uses in his car. He said Mobil One. I said how about the other oils. He replied, look I have been designing oil and additives for 28 years. I use Mobil one. You should be using it.

It is fantastic oil with properties that far exceed mineral oils.

On a second issue, oil companies change their oil all the time without admitting there is something different about the oil. Some mineral oils used in large machines used to be group 1 oils. They were changed to group 2 oils and the trade name stayed the same. Turbines began to show varnish problems. Wrong additives were put in these oils, but the name remained the same. New additives were put in the oil and still no change. There is no way to be sure about oil additives and oil design, because the oil companies constantly change the design, but say it is the same old oil you love.

I use Mobile One, You should use it.

Jeff_Keryk

Personally I would find and fix the leaks, one at a time.
I would use the viscosity the engine calls for.

Duane4238

So, did anyone realize this thread was from 2010? I hope he fixed his leaks by now, and figured out what oil to use.
Happy Thanksgiving, all.
Duane

C2C3PO

With all the "resurrected" old threads today one would think Easter was fast approaching....
On the bright side, at least it proves people know how to use the search function !

kjbuster1

I've used Mobil 1 in rebuilt engines in '65,'66, and '72 BB engines with no problems.