tigertank

I was wanting to put all synthetic royal purple in motor trans and rear diff..... but I was told this could caus leaking issues on my 82 crossfire all stock motor??

Sunstroked

synthetics are compatible with the engine seals. So thats not an issue. But they do seem to weep past seals easier than petroleum oils. I use synthetics exclusively in all of my cars and motorcycles.

REELAV8R

Royal purple I can see using in the rear diff and the transmission as both will be in there for a long time.
In the motor I find it cost prohibitive.
A stock motor doesn't need to have synthetic. I use and advocate the use of synthetic if it makes sense. In other words you drive it enough to benefit from the extended change intervals or you have a high performance engine that you want a little bit more protection for.

For a stock motor the benefits are limited, but synthetic is still superior to conventional oil. It flows better on cold starts and helps to moderate the wear to the cylinder walls better than conventional can. Has a better high temp tolerance for areas that get really hot, like the exhaust valve or anywhere that lots of pressure is present.

I would use a cheaper alternative as you will be changing engine oil much more frequently than the trans or rear diff fluids.

Mobile one 0w40 at Walmart is $27 or so for 5 quarts. I wouldn't use just any synthetic with a flat tappet engine. You want that 1000 PPM of zinc. 0w40 does have that. The other Mobile one oils do not unless you go to 15w50, but that's a bit thick for most folks. If you got a high mileage engine it may be just right.

Leaks, no. Unless you got bad seals anyhow and only the gunk trapped in them is preventing it from leaking. The detergents in the oil may clean the gunk out and that could result in leaking.

doorgunner

My suv engine with 60,000 miles on it "burned" the synthetic oil/1 quart every 3,000 miles when I switched from regular engine oil.

I wonder if other members noticed this problem with older engines.

ddawson

Yes, I was getting blue smoke at start up when I switched. The smoke went away when I went back to dino.

When I removed the intake I found the gasket at the bottom at the runners was seeping oil because it didn't seal well.

With the new engine and fresh seals I'm back to synthetic.

crawfish333

I have used synthetics on my newer Vettes for many years, but those engines were designed to use Mobil 1. These lubricants did not exist when my 72 was built, so I use regular Quacker State motor oil on it.

Just seems to make sense.

OLE442

I have a case of synthetic/dino blend oil sold by Hemmings that is supposed to have additives in it that aren't in the new oils and its for 60's & 70's engines. They say new oil can mess up the older engines d/t not having certain additives!

Anyone have any thoughts on using this oil in either my 1976 C3 or my 1972 Cutlass 442?

pmr2000

So what ZDDP PPM is enough for our old 350's?...1200?

doorgunner

FYI: Back in the day Quaker State was pitiful/destroyed many engines with internal "gook" buildup.

I hope they have improved it greatly since then. There are many good threads about engine oil.

REELAV8R

1000 PPM seems to be the magic number for a stock flat tappet engine. M1 0w40 has 1100.
If you have say and "extreme" comp cam or the voodoo line cam you may want more in the 1200 to 1300 range. M1 15w50 has 1300 PPM I believe, you can look it up to confirm it. Break in for a flat tappet should be per the cam manufacturer, and may require higher levels of zinc.
I just suggest Mobile 1 since it's easy to come by, has some quality oils and is affordable. There are of course many other oils that will meet the requirements of a flat tappet engine.

Keep in mind that more is not necessarily better. Too much zinc and you will have another set of problems. Racing is a different story and is not related to street driven cars. They change their oil more frequently than most street driven cars. The racing oils may have a much higher level of zinc.

Here is an article that explains zinc use a little.

https://blog.hemmings.com/index.php/...older-engines/

pmr2000

Hmmm I am ready for first oil change, have both Mobil 1 and Vavoline VR1 to choose from....just picked up stock 80k mile L-48 right now no leaks or drips...


Should I put dino or synth?

REELAV8R

Depends on how and when you intend to use the car. Also on a cost basis 10w30 VR1 is about $6 per qt. So $30 for a change.

M1 is $27ish for 5 qts, so slightly cheaper.

On an 80,000 engine if I used it in warm weather primarily and/or it's a bit loose, I would go with 15w50 M1. If it's a tight engine or use it in winter weather I would use the 0W40. On a 80,000 mile gen 1 SBC it's likely got some good wear by now.

If you drive plenty then you can also take advantage of the increased change interval for synthetic. 5000-10,000 miles. I go 10,000 on my dd's and change the filter at 5000 miles.
In my vette I use the 0w40 M1. It's a newly rebuilt tight engine with a roller cam and change it annually.

VR1 is a good oil as well. If you got it I would use it one way or the other Change interval would likely be shorter. That may not be a factor though if you drive less than the change interval in miles per year.