Engine Oil Test

Ok boys. I’m going to take one for the team and go get a couple of data points for us because I don’t recall seeing a thread quit like this. I’m going to take my wife’s car, who is due to have her oil change, and take a sample and try a different oil. Here are some facts.

1. Her car is a 2019 Subaru Outback.
2. Next oil change to be performed at 35,000 miles.
3. First 5,000 miles was OEM oil.
4. 5,000 to 25,000 was Royal Purple.
5. 25,000 to 35,000 is Amsoil Signature Series.
6. I will get an oil analysis on this Amsoil.
7. At 35,000 I’m going to use Supertech 20,000 from Walmart.
8. I will perform a second oil analysis at 40,000 on the Supertech.
9. We will compare the two results.
10. 5 quarts of Supertech before sales tax was $19.98.
11. 5 quarts of Amsoil before sales tax is $56.45.
12. Amsoil also carry’s a $10 membership fee every 6 months.
13. All Oil is 0W-20.
14. New filter changed at every interval.

I am expecting/hoping to find no appreciable difference in analysis results between the two and rather than guessing or giving an opinion I will let the data speak. Might there be anything else I should consider that all you might find helpful?

 

I don't think you're really going to prove anything running either oil for < 10k miles.

The additive packs in the oil might be a little different, but it's pretty widely accepted that specific brand oil doesn't really matter. All oils with an API rating in the oil weight spec'd for your vehicle will perform fine under most oil change intervals. It's hard to buy bad oil these days.

If you just want to see what's different between the oils I'm sure you can find virgin uoas for these oils (and lots of others) on the BITOG forums.

https://bobistheoilguy.com/forums/forums/virgin-oil-analysis-pcmo-hdeo.11/

 

I think a taste test will provide us with all the information we need.

 

I guess the point would be you don’t have to spend more on expensive oil to achieve similar results.

 

I think this has already been proven. Supertech oil, Amazon Oil, and Kirkland brand oil all get great uoas on the BITOG forum. People on this forum just like to argue about oil. I say save the $100 bucks on the tests and buy something cool for your truck.

 

You don't really have to do this man. There has never, in recent times, been an engine failure caused by the brand of oil. As long as they are certified and the right viscosity and kept full, it will give you the same result in 10K or 5K miles.
Now, if you get two identical vehicles, drive identical miles identical ways, drive for 200K then tear them down, you maybe might see a slightly different result but not failure due to brand.

 

But that’s boring. Let Mr. Mquibble do his thing and amaze us with the results. I like the guy.

 

Shhhhhhhhhhhh

 

OP, if I recall correctly you’re an engineer. You’ve been through, well, school and stuff. You’ve been educated on the scientific method.

So I would think you already know that the results of this test are meaningless because the sample size is absurdly small and you would really need to run one oil in one engine for an extended period. Let’s say you switch to oil X, and the sample starts showing engine wear. Ok, so can you conclude that it’s because of that oil? Wait a minute…some of the engine time was on other oils. Are they partially responsible? Or maybe it’s just a lemon of an engine? Are you going to tear your wife’s engine apart afterwards and conduct an engineering investigation to rule out all the other potential contributing factors?

Go with a proper methodology on a thousand engines over minimum 100k miles per and control for other variables and then I’m interested.

Maybe ten thousand engines.

 

Yep. Kind of the point. Thank you.

 

I like super tech conventional. I can tell when it's time to change the oil at 3,000 miles because the valve train gets noisy