Viper engine oil qustions 10/30 or 0/40
Discussion
From Tom on the VCA
An SAE 0W-40 would be better.
The "0W" label only means something at very low temperatures; in this case that the oil allows good engine cranking speeds down to -35C and good oil flow through the oil pickup tube at -40C. It means nothing as far as warmed up temperature operation.
The "40" means it is thicker than a "30" when at the warmed up oil sump temperature. However, there is "fluid friction" and so an SAE 40 will have slightly more drag in the bearings than an SAE 30. What the OEMs have done with better precision manufacturing equipment is to make surfaces more uniform, which lets them make clearances overall tighter, and then allows the use of oils with less fluid friction, like the oil designated for the 5.7L HEMI engine - an SAE 0W-20.
Pressure is not relevant other than indicating the energy needed to place the oil where it is needed. The general "10 psi for every 1000 RPM" comes from having to push the oil against the centrifugal force inside the crank so that it reaches the next crank throw. Once the oil is positioned ahead of a spinning journal, it will get pulled in anyway. The 60 psi out of the pump is not going to make much difference to the 10,000 psi pressure under the journal.
An SAE 0W-40 will therefore allow better starting, better fuel economy when warming up, and slightly poorer fuel economy when fully warmed, but with a thicker oil film - meaning directionally better engine protection.
OEMs did have the choice of an SAE 5W-40 in the past, a viscosity grade favored by the Europeans. Now that SAE 0W-40 is available, it will also be formulated for Euro applications, meaning it will have more additive than typical SAE 10W-30 oils. That alone is worth the switch.
______________
Tom,
Fuels & Lubes Geek of the Realm
http://forums.viperclub.org/rt-10-gts-discussions/...
Looks like we can get the oil in the UK.............
An SAE 0W-40 would be better.
The "0W" label only means something at very low temperatures; in this case that the oil allows good engine cranking speeds down to -35C and good oil flow through the oil pickup tube at -40C. It means nothing as far as warmed up temperature operation.
The "40" means it is thicker than a "30" when at the warmed up oil sump temperature. However, there is "fluid friction" and so an SAE 40 will have slightly more drag in the bearings than an SAE 30. What the OEMs have done with better precision manufacturing equipment is to make surfaces more uniform, which lets them make clearances overall tighter, and then allows the use of oils with less fluid friction, like the oil designated for the 5.7L HEMI engine - an SAE 0W-20.
Pressure is not relevant other than indicating the energy needed to place the oil where it is needed. The general "10 psi for every 1000 RPM" comes from having to push the oil against the centrifugal force inside the crank so that it reaches the next crank throw. Once the oil is positioned ahead of a spinning journal, it will get pulled in anyway. The 60 psi out of the pump is not going to make much difference to the 10,000 psi pressure under the journal.
An SAE 0W-40 will therefore allow better starting, better fuel economy when warming up, and slightly poorer fuel economy when fully warmed, but with a thicker oil film - meaning directionally better engine protection.
OEMs did have the choice of an SAE 5W-40 in the past, a viscosity grade favored by the Europeans. Now that SAE 0W-40 is available, it will also be formulated for Euro applications, meaning it will have more additive than typical SAE 10W-30 oils. That alone is worth the switch.
______________
Tom,
Fuels & Lubes Geek of the Realm
http://forums.viperclub.org/rt-10-gts-discussions/...
Looks like we can get the oil in the UK.............
Edited by V1PER on Wednesday 21st May 12:42
Gassing Station | Vipers | Top of Page | What's New | My Stuff