I would like to know which one would be better in blending engine oils -- a straight SAE40 or a lower viscosity base oil added with VI Improvers? I know that VI Improvers don't lubricate, can someone explain more on this?
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It depends on what the final oil is to be. To blend an SAE 40 oil I would think you would want to use base oils with viscosities as close to the target viscosity as possible.
If you are trying to blend a multigrade, then you have trade offs with conventional oil (synthetic is much better). For example, to get a 20w50 you might use base oils near a 30 weight and add viscosity index improvers to get the 50 rating. You may also need some pour point depressants to get the cold properties of the 20w.
Adding some synthetic base stock would increase the viscosity index thereby reducing the amount of viscosity index improvers and/or pour point depressants needed.
Some synthetics have a high enought viscosity index that they already meet the multigrade criteria without any viscosity index improvers. I am told that of Redline's multigrades, only the 5w40 has any viscosity index improvers. Redline Oil is ester (Group V) synthetic.
If you are trying to blend a multigrade, then you have trade offs with conventional oil (synthetic is much better). For example, to get a 20w50 you might use base oils near a 30 weight and add viscosity index improvers to get the 50 rating. You may also need some pour point depressants to get the cold properties of the 20w.
Adding some synthetic base stock would increase the viscosity index thereby reducing the amount of viscosity index improvers and/or pour point depressants needed.
Some synthetics have a high enought viscosity index that they already meet the multigrade criteria without any viscosity index improvers. I am told that of Redline's multigrades, only the 5w40 has any viscosity index improvers. Redline Oil is ester (Group V) synthetic.
