Oil recommendation for my 1970 dodge dart with 318 engine
Hey guys what do you guys recommend for my 318 as far as oil grade and brand goes? I live in Houston so gets pretty hot down here...Haha any help would greatly appreciate it!
I'd say use what was recommended in the FSM or owners manual for always above 32 F, or for as low as 0 or 10 F whatever is appropriate.
However some years the factory was quite liberal in the recommended grades. I'm looking at '75 owners manual - pretty anything goes!
I know '69 FSM is a bit more specific.
Temperatures consistantly above 32 F:
straight 30, 10W-30, or 10W-40 or 20W-40.
For year round use where temperatures may occasionally go as low as -10* F
10W-30, 10W -40
I agree with using the oil pressure gage as your guide.
When the engine is heat soaked, if its holding the minimum pressure at idle of 10 -15 psi and most important its going up so its got 50 - 60 psi driving at 60 mph, your good. If its struggling to do that, then go up on the grade, or find an oil with better hot viscosity within the grade.
In short, Grade indicates the minimum and maximum viscosity allowed at 212*F
and W grades are indicators of colder temperature viscosity, which in recent years have a more complex set of specifications than back in '68.
The key thing, as you probably have observed, is that oil viscosity is very temperature dependent.
>Pick one that's heavier than needed, and when its cold, imagine trying to push honey through a straw. Pressure at the pump may be high but not much is making it through to the top.
>Pick one that is too light, and when hot there isn't enough pressure to properly support the bearings.
So that's why paying attention to engine temperature and pressure is useful in determining if a change is needed.