synthetic blend
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Senior User
Joined: Oct 2006
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synthetic blend
im changing the oil in my 351 cleveland and dont want to use full synthetic because im afraid it will leak as the seals are cleaned. Is a synthetic blend a better way to go with an older engine (1972) or just a waste of money?
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Joined: Jan 2004
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From: SW Va
Well if potential leaks are such a worry, you could sorta sneak up on the synthetic thing, by considering using a "high mileage" recipe oil, for a change or two, as they have seal softening agents in them,, that may be able to soften & or swell any potential seal leaks.
Then you could try a blend & see how that goes, then maybe a full synthetic, if your of a mind to use that in the end.
Perhaps you may also need to pay attention to the phos & zinc levels in the lube you choose for this older engine, as the newer SM oils have had those additives cut back & there are questions about possible cam lobe wear on older engines, on those oils that haven't had their add pack recipe adjusted, to make them backward compatible.
Some say there is likely no problem, unless your racing, or have a high lift cam, or high oil shear engine desgn.
Just some things to ponder.
Then you could try a blend & see how that goes, then maybe a full synthetic, if your of a mind to use that in the end.
Perhaps you may also need to pay attention to the phos & zinc levels in the lube you choose for this older engine, as the newer SM oils have had those additives cut back & there are questions about possible cam lobe wear on older engines, on those oils that haven't had their add pack recipe adjusted, to make them backward compatible.
Some say there is likely no problem, unless your racing, or have a high lift cam, or high oil shear engine desgn.
Just some things to ponder.
Posting Guru
Joined: Jun 1999
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From: Northern California
Full synthetic oils are much, much much better with seals than they were even 10 years ago. 70s and 80s, a night and day difference.
Now if you have, old, brittle valve cover gaskets in a '72 motor, that is one thing. However, modern synthetic oils will not cause normal seals or gaskets to leak, based on it's oil content alone.
I've used 5w30 oil, both Mobil 1 and Royal Purple in an '87 Aerostar van. 140K, 3.0V6. Van is garaged nightly, and the garage gloor is spotless, never a leak or oil consumption in this engine, using full synthetics.
Ed
Now if you have, old, brittle valve cover gaskets in a '72 motor, that is one thing. However, modern synthetic oils will not cause normal seals or gaskets to leak, based on it's oil content alone.
I've used 5w30 oil, both Mobil 1 and Royal Purple in an '87 Aerostar van. 140K, 3.0V6. Van is garaged nightly, and the garage gloor is spotless, never a leak or oil consumption in this engine, using full synthetics.
Ed
Senior User
Joined: Dec 2006
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I agree, synthetics have been out of the dark ages for some time now. You can use a blend to start with, or go whole hog if you feel daring.
Either way, if you wish, at the first sign of the slightest weep, seep, or leak, you can go back to conventional oil with no further worries.
If your older engine is historically or personally valuable, oil analysis would be a good thing for keeping track of how your oils are working in your motor. Some oils work better for a particular engine than others.
Since your engine has lasted this long on regular conventional oil changes, it would be safe to continue them. However, synthetics can work just as well, and better in many instances.
Either way, if you wish, at the first sign of the slightest weep, seep, or leak, you can go back to conventional oil with no further worries.
If your older engine is historically or personally valuable, oil analysis would be a good thing for keeping track of how your oils are working in your motor. Some oils work better for a particular engine than others.
Since your engine has lasted this long on regular conventional oil changes, it would be safe to continue them. However, synthetics can work just as well, and better in many instances.
