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Oil Recommendations for hemi  

Active Member

Just wondering if there is a general consensus on what the best type of oil is to use in a 56 DeSoto.  Synthetic, conventional, blend, high mileage, weight of oil, add zinc additive???  As far as I know the engine has never been rebuilt.  Odometer reads about 95k.  Car is stored from Nov-April.  I have been using 10W-30 conventional oil and adding a zinc additive, but I'm thinking it might be beneficial to start using a high mileage oil and still add the zinc.  Engine burns a minimal amount of oil, but nothing noticeable.  It does not tend to overheat, unless idling for very long periods of time on a very hot day. 

Posted : May 4, 2019 5:12 am
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The zinc additive isn't really necessary.  My engine rebuilder, who would have to make expensive warranty repairs if he was wrong, only requires a zinc additive in the first 2 oil changes on his rebuilds.   After those oil changes, he allows any oil of choice and specifies no additives.

There's a big debate about that, but under those circumstances, my opinion is that the additives are not necessary on used engines, and only for the 1st couple of oil changes on a newly rebuilt, non-high performance engine.

You might consider popping the valve covers and seeing how gunked up things are with old oil.  If you decide to use a high detergent oil, or a synthetic, you might run the risk of loosening the old gunk, and potentially plugging up passages.

It's supposed to be fun!
1949 De Soto Custom Convertible (project)

Posted : May 4, 2019 5:04 pm