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Type of Motor Oil?


Dodge51coronet
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This has been argued many times in these fora. Use a 5 or 10W-30 or 40 diesel oil (CI-4) to get the full zinc ration. CJ-4 has less zinc but is OK. Look for Richard Widman's paper on the fora about oil for his Corsair or try http://www.widman.biz/Corvair/English/Links/Oil.html.

 

You want a 5 or 10W so you get rapid oil pressure buildup when starting from cold. The second number is for when hot. The W does not mean "weight" it means "winter", i.e. cold.

 

It is a myth about non-detergent oil in the engine. If it has such oil, it will be filthy inside, everywhere, with buildups of muck in all the wear spaces (e.g. ring grooves) and there will be sludge in the sump. Clean out the sump and put in a detergent oil, change at 1000 miles or sooner if dirty and do the same again. After a couple of changes it will be much cleaner everywhere in the engine. The materials that will scour bearings are heavy and will settle out in the sump and if you have them your engine is in trouble and you have a serious problem anyway. The super-fine combustion products and other dirt won't harm the bearings and will drain out when you change the oil.

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And don't forget to change the oil filter each time.

Only really needed on full flow filters: If they clog up an internal bypass opens and all the gunk they have collected goes into the bearing. Since you can't see inside the filter to determine if it is filling up, safe practice requires replacement at every oil change.

 

That car was fitted with a bypass filter. If it clogs up then oil simply stops being filtered but the gunk the filter collected stays put in the filter. Good practice is still probably to replace the filter fairly often (5K or maybe 10K miles) but not necessarily more frequently. If the car is setup for using the disposable canister with a depth media (fairly common on Chrysler built cars of that era) then this is especially true as those filters are becoming a little scarce so throwing away one that is not totally used up is a waste. If it is fitted with a replaceable element filter, then those elements are readily available and you might as well toss a new one in on each oil change.

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I'm TOTALLY a detergent oil proponent but don't jump the gun just yet.

Drive it first to determine whether or not it IS an oil burner.

If you can comfortably determine the engine is tight by all means switch to detergent oil.

If it turns out be something of an oil burner stay with non-detergent oil.

Probably the only thing keeping it from being a BAD oil burner is crud in the ring grooves which detergent oil WILL remove after a time.

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51 coronet, google "non detergent oil zinc" and plan to read for a few hours. The best article I've read on this subject was written by Lake Speed's son and appears on Joe Gibbs site. It compares detergent to zinc.These old contraptions don't need zinc because the valve spring tension is not high enough to warrant it. Stay away from opinions and read what engineers say about this subject and then do exactly what you want. You will ultimately be paying the bill.

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