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I recently bought a 68 with a 350, Trick Flow top end, @400+ HP. The previous owner said he used Royal Purple motor oil, but I am a bit unsure of what weight I should use. I live in Nor Cal, so the weather usually doesn't get too hot or too cold(although it has been hot as hell lately). Should i go 10w30? 5w30? 10w40? Any input would be appreciated. Thanks
 

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if it stays hot, use 10w 30, but there really isnt much of a worry, 5 30 or 1030 would work just fine, the only real problem occurs if your engine is worn down real bad, your piston seals are leaking, you have a head leak or distributor leak etc. the 5 might leak out faster than 10, as its thinner.

or is it the other way around? i cant remember to be honest,

as for oil companies. oil is oil is oil. the only difference is additives, several companies are supplied by the same refineries, and royal purple is good and all, but if all you need is to lube up your engine, any oil will work. and really, any weight will too. the only real time i can think of were type would matter is in cold weather


feel free to correct me if i am wrong though.

i wont claim to be all knowing
 

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As prarie kid said, oil is oil. I used to make fun of a buddy who swore religiously by royal purple because he said it was race oil. He loved to put it in his honda civic for that reason. Stock motor and everything. Never thought it made a difference but hey, he can pay $7/qt if he wants to. I used to use only mobile 1 in my truck.

The nova always gets 20-50w conventional, the cheapest junk I can find. Just remember when selecting weights that your going for the 'operating temperature' oil viscosity.

I say this because I warm the car up and take it out for a spin with the 194cid and power glide, and I have 40psi at idle. Ill take that car on the freeway and hold it at 70 for a few miles, the next time I stop at a light the oil pressure will drop to less than 10 sometimes because it is so thin and the bearing clearances are worn. Imagine if I was running a lighter grade what would happen?
 

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HAHA what a douche bag I am! I forgot to mention that my Nova only runs 20-50W Race oil for the ZDDP:eek:

Guess thats a small detail worth NOT leaving out:eek:

Hey Rick, motor install next weekend hopefully....Would it be possible to borrow that leakdown tester for a day or so?
 

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Sure not a problem. Let me me knows whats up. RICK
 

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and thats what i meant by the only difference being additives, if you dont need any special additives, oil is oil, and the additives are just protection.

if you are only concerned about weight, and tempurature, just use 10 30. it wont get too coold and make it thick thats for sure.
 

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To clarify the "oil is oil is oil" comments. It's a fairly true statement except that there is actually a real difference between conventional oil (derived from petroleum base) and Synthetics. Conventional oils are refined to remove contaminants such as wax and sulfur. Conventional oil companies try to remove the maximum amount of wax possible during the refining process but 100% removal is impossible.

In this case, Royal Purple is a synthetic oil which will out perform a conventional 9 times out of 10. If you're simply worried about the oil flowing at cold temps, you should be fine with either weights unless it gets to -24 degrees where you are in Nor Cal. :eek:

I'd be more concerned with the additives, Most RP oils are developed for new engines with better tolerances and clearances. I rep for AMSOIL and we introduced Z-Rod which has a High Zinc Formula for Classic and high performance engines with flat tappet cams like yours. I'd suggest the 10w-30, It flows at -45 degrees which should be more than adequate. There are also rust inhibitive additives in the Z-Rod oil to help protect the engine during storage.
 
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