Got a bunch of oil cheap. Which is best of these 2?

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Dec 6, 2024
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Long time lurker, first post. I'm not asking about the best oil in general, I don't want to burn this thing down lol. Just between these 2 oils. I've searched but not gotten enough of an answer anywhere.

Valvoline Advanced Full Synthetic 5W-30 and Castrol GTX Full Synthetic 5W-30 Motor Oil.​

I always have a stock of the valvoline in my shop but just got a ton of the castrol for what I think is a great price. I I have all GM vehicles, 1 SUV and 2 trucks. 2020 and a brand new 2025 6.6L gas for towing trailers occasionally. None will get worked super hard. A few thousand miles each per year. Basically of these 2 oils I have what's your opinions of the winner? Just figure I might as well save the better for the new truck. Both are dexos 1 gen 3 full synthetics, so I figure they are about the same myself but i know there are people much smarter than me with this here.

Thank you very much.
 
If given that choice I'd choose the Valvoline because the Castrol is their entry level synthetic but in reality they probably are very close in quality.
 
great, thanks. just wanted to be sure my assumptions were correct. one of those weird ones where i'm staring at 2 different stacks of jugs and wasn't sure if one may be better.
 
Definitely mix them! Otherwise your engine will explode when you run the lesser of the two. :)

Seriously though, I've run both of them separately and mixed together, mixed with other brands, mixed with different viscosities, etc. You and your engine will never know the difference. Great score if you got the GTX at a good price!
 
When I had Valvoline advanced and Castrol edge both in synthetic 10w30, non scientifically the edge seemed thicker than the advanced at room temp, and the Castrol bottle says 10x better high temp performance so with that, I use the Castrol edge during summer and the Valvoline in winter and /or summer. I have one more jug of the Edge in my stash. Will use it in the dead of summer. In your case, both good oils you can run anytime in all your GM trucks
 
I’ve run that Valvoline oil, just in a 5w-20 weight, in my mustang for over a year and over 10k miles. I have the UOA result posited, it did great. I wasn’t tuned into oxidation testing when I did that run but from all other metrics the oil held up fine.

I’ve run long intervals with Castrol Edge, not GTX, and it did great. Haven’t run GTX but I’d be shocked if it didn’t also run great.
 
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