Besides it being the recommended weight by APS, it is thicker and I guess better for the turbos and the heat the give off. I should hopefully never have any issues burning oil because it's too thin. Some might complain about their cars starting differently or not as easily with the thicker oil...so what I do out of habit is turn the key halfway and wait for all of my gauges to come up...then fully start the car.

I tried to buy Mobil-1 since I figured it's easier to come by, and found out they don't make a 10w-40 Mobil 1 unless you get it with added preservatives, etc. So I ordered up enough quarts of AMSOIL to last me about 5 oil changes.

I think a lot of people just use what they can find and just end up using something thinner and easier to come by.

 

As per SGP's recommendation I am using straight 30 weight non synthetic....Castro or Valvoline.

 

I use 20-50 Royal Purple

 

Then why don't you use a 50/50 mix of 15w50 and 5w30 of Mobil1? Those are readily available everywhere and would give you a 10w40 grade as per APS recommendations.

 

i never heard that in my life either!!!!!!!! RP is the last to thin out!!