I'm an amsoil lover so I'm partial to them but.....About you being confused on the branding. You want the Signature series, it's their top tier oil. It uses true synthetic base stock(group IV/V oil) This is why I hate the off the shelf so called synthetics such as Syntec, Mobil 1 and others that are "fake synthetic" meaning they are refined petroleum which is hydro-cracked group III oil.
The OE and XL line are cheaper alternatives that meant to compare to the mainstream brands and benefit from some of the AMSOIL additive package. They have lower "total base number" than signature series which is supposed to be pretty important but I can't tell you why. They don't offer as long of an oil drain interval because of not using the true synthetic base stock.
There are others that use a true synthetic base stock...Redline and top tier Royal purple. One of the best things about true synthetic base stock is it simply does not shear or lose viscosity. When an oil shears, what you think is 30w may actually be 20w or less depending on how much it has sheared and it happens easier than you think and when the oil has broken down....The color of oil means nothing.
