oil weight

[booyaballer]

i'll be changing the oil in my 70 challenger which has a 360 crate engine. The manual says 10-30 is what is recommended which would be if the car was new. being that the engine is from 93, would that change or stick to the same 10-30?

for whatever reason, the last time i put 20-50 in it, though i don't recall why but it definitely had zinc in it.

still learning so i'm open to any advice.

Thanks.

 

[Ricks72Chlgr440]

Is it a flat tappet engine? If so you definitely want oil with zinc. What is your oil pressure hot? You can keep using that 10/30 oil but I would use quality 10/40 to give a little better hot viscosity.

 

[540HemiCuda]

Valvoline VR-1 Racing is probably the best and most cost effective oil for flat tappet engines. It's ALL I have used it in my wedges and Hemis for many years.

The best test for choosing the right viscosity is to take readings with the oil you have in the engine now at operating temperature. 15 pounds at hot idle and about 60 pounds max is all you need. And your old oil will probably read a little lower than fresh oil will. I run straight 30 VR-1 racing in my Hemi just like I have in my big inch wedges. Never a problem. But if you like a multi better than a straight weight, then use that. I have an Accusump to pre-lube the engine before I hit the key, so multi grade oil does not have any advantage for me.

 

[Chryco Psycho]

SJ Or at worst SL is the only oil to use , ZDDP is more important than the weight , Agricultural oils from farm supply are all SJ as they are off road use .
the engine clearances are generally created for a given oil , more clearance for heavier oils & tight for lighter oils , I typically used 10/40w before all of the oils had the Zddp removed