TrailBeast
AKA Mopars4us on Youtube
We know oil has to create a film over the bearing surfaces and metal to metal contact surfaces.
What most don't think about very much if at all, is that oil flow over the metals carries off heat.
One myth is that the higher the oil pressure the better, but this is totally false in most cases and can lead to premature engine wear.
So how do you tell what viscosity is best for your motor?
Here's the way I go about deciding.
When you start an engine cold what does your oil pressure read? (probably 60-80 lbs)
When the engine warms up all the way what does it read when you rev it?
If the pressure climbs to the same maximum pressure warmed up and at 3,000 or so RPM's you are using to thick of an oil.
Remember, oil volume for carrying off heat is almost more important than pressure, so if your oil psi hits the same lbs warmed up and at RPM's you are wasting power and probably also getting less flow over the metals to carry off heat.
Also once the oil pressure reaches it's maximum any more pressure than that is being bypassed inside the oil pump wasting volume.
Usually the ideal oil viscosity is one that hits your normal cold psi, and then almost hits that same number at RPM's.
This insures the pump is able to reach it's max pressure and volume both and is able to flow as much cooling volume as possible.
Another way of thinking about this is this.
If 40wt oil shows 80psi cold idle and 80 psi hot at 3k and flows 25 gallons a minute, 30wt oil might show 50lbs hot but flow 30 gallons a minute.
That is 5 gallons a minute of cooler oil flowing over your metal surfaces providing better lubrication as well as better heat removal.
I would rather have a lower pressure that guarantees the full volume the oil pump can flow.
What most don't think about very much if at all, is that oil flow over the metals carries off heat.
One myth is that the higher the oil pressure the better, but this is totally false in most cases and can lead to premature engine wear.
So how do you tell what viscosity is best for your motor?
Here's the way I go about deciding.
When you start an engine cold what does your oil pressure read? (probably 60-80 lbs)
When the engine warms up all the way what does it read when you rev it?
If the pressure climbs to the same maximum pressure warmed up and at 3,000 or so RPM's you are using to thick of an oil.
Remember, oil volume for carrying off heat is almost more important than pressure, so if your oil psi hits the same lbs warmed up and at RPM's you are wasting power and probably also getting less flow over the metals to carry off heat.
Also once the oil pressure reaches it's maximum any more pressure than that is being bypassed inside the oil pump wasting volume.
Usually the ideal oil viscosity is one that hits your normal cold psi, and then almost hits that same number at RPM's.
This insures the pump is able to reach it's max pressure and volume both and is able to flow as much cooling volume as possible.
Another way of thinking about this is this.
If 40wt oil shows 80psi cold idle and 80 psi hot at 3k and flows 25 gallons a minute, 30wt oil might show 50lbs hot but flow 30 gallons a minute.
That is 5 gallons a minute of cooler oil flowing over your metal surfaces providing better lubrication as well as better heat removal.
I would rather have a lower pressure that guarantees the full volume the oil pump can flow.
