10W40 too light?
Not sure what you mean by 'studies'. This is straightfoward engineering. Go look at the specifications for SAE Automotive oil grades. The grade designations are based on viscosity at 100 * C or 212 *F. An SAE 30 most certainly has a different viscosity at 200*F than an SAE 20 or 40.
If you want to know precisely the viscosity of any oil, the manufacturer's data sheets are available, or you can send a sample for testing. The relationship of oil viscosity with temperature is consistant and can be graphed with an equation using any two temperatures within reason. Yes, once an engine is warmed up, the difference between different grade oils is far less than when starting cold, but that doesn't mean its not important. Especially at high rpms and loads, an oil must be in the best working range or stuff will not survive.
Here's a graph of viscosities for four of Brad Penn's oils as an example of the differences. (graph program at Widman's website)
Not sure what you mean by 'studies'. This is straightfoward engineering. Go look at the specifications for SAE Automotive oil grades. The grade designations are based on viscosity at 100 * C or 212 *F. An SAE 30 most certainly has a different viscosity at 200*F than an SAE 20 or 40.
If you want to know precisely the viscosity of any oil, the manufacturer's data sheets are available, or you can send a sample for testing. The relationship of oil viscosity with temperature is consistant and can be graphed with an equation using any two temperatures within reason. Yes, once an engine is warmed up, the difference between different grade oils is far less than when starting cold, but that doesn't mean its not important. Especially at high rpms and loads, an oil must be in the best working range or stuff will not survive.
Here's a graph of viscosities for four of Brad Penn's oils as an example of the differences. (graph program at Widman's website)
