I am stunned that nobody is talking about AMSOIL
They have good oil too. It is just for laugh
Buy the was if you had a look on the data posted in 4th above post you would see that 10W30 is a ligther oil. Actually it harms less the engin when you start it up at 60F outside temperature. I really don't get why people say that the 0w40 is ligther ?!?!
The advantage of the 0W40 is the pour point. I think it is -70F ! WHO WILL DRIVE HIS VIPER BELOW -20F ? At -20F you speen the rear wheels in 5th gear ... The 0W40 can be used in extreem cold. In Canada when the temperature drops below -30F we need to use one of these extreem oils. Personnaly I believe it was a Daimler pressure to swith the Viper to 0w40. I am still wondering why a performance car runs on this extreem oil ? A 5W40 oil would be perfect too. MB run from -40F to 120F. They are daily driver cars. Nobody will drive a Viper on the North pole !
The best way to understand the viscosity change effect on the oil is to test different tranny oils in the Viper transmission. For instance during the winter we sometime swith to full ATF3 oil in the manual transmissions. The ATF is good to -60F in the trannies. The best place to feel the difference of the temperature on the oil is the Viper transmission. All other major trannies run double synchros so they will not suffer so much from viscosity change. When the temperature is lower at 40F, Try to drive the Viper with ATF3, Light Syncro 75W85 and 75w90 Manual tranny oil. You will feel the difference instantly ....
Double syncro trannies will feel the viscosity change below 10F. For instance a Mercedes tranny will get sticky at 10F.
Now imagine this "sticky" effect within the Viper engin with 5w30 oil, 10w30 and 0w40 oil. When engin is cold it uses the most.
The worst is when you run the engin with all these "lower" temperature modifications. For instance I use a 170F thermostate. My engin runs at a lower temperature. If I use a 0w40 or a 5w50 it would be too thick for highway. So I run my engin with 5w30 which viscosity should be similar to 0w40 at 170F. I just started to regret my 170F a couple of weeks ago ... I destroyed the bearings in my viper transmission at 12000mi. It was running too cold at 140F with a too thick tranny oil ...