Back in 2016 shortly after I did the 2zr-fe swap into our Yaris, I sent in a oil sample to be analyzed. I ran the AMSOIL 10W40 for a full 6000 mile interval in my daily driver/weekend autocross swapped Yaris. I did not attend any track racing events during this sample, and I was not using an oil catch can yet. Another thing worth mentioning is that the car still had an automatic transmission, even though I manually shifted it when racing or doing spirited driving. I think that's all of the details so lets take a look at the sample results:
If you look at the comments you'll see they mention the viscosity is slightly low, but aside from that it's a clean sample. I thought it was strange that the Amsoil viscosity didn't hold up in a well maintained Toyota engine, but hey the sample was clean so who cares right? I decided to change my oil every 5000 miles instead and didn't take another sample for a whole year.
Fast forward to 2017 and Ive decided to run the MOBIL 1 10W40 for the sole purpose of comparing test results. We ran this oil for the entire autocross season and 1 track event with TRD cup...with 2 drivers at every event! The car is no longer a daily driver, it is only driven to races and back. It had a 5 speed manual transmission at this time, and we ran a oil catch can for the whole season. I'm not sure how many miles we put on this oil either, maybe I should log them in the future. Oh well, lets look at the sample:
Here again we have the mention of low viscosity in the comments and this oil was run for a significantly shorter time. Aside from that you can see that the wear and multi-source metals look about the same on both samples: Iron, Aluminum, Molybdenum, and Boron. The differences in additives is because these two companies use their own formulas, so there is no way to say either is better than the other. Contaminants are showing a large increase in sodium, this could mean there is a coolant leak somewhere or that could just be part of the Mobil 1 formula. Since my car has never overheated, I'm not going to worry about this unless the number goes way up next time.
There are many factors at play here, but one thing remains constant...low viscosity. Since there was no mention of fuel dilution or any other extreme contamination, I feel like both of these oil products may be inaccurate in their viscosity claims. Other than that both oils did their job and protected my engine even under constant load and high cornering forces, so I'd say these products provide the same amount of protection.
So I ask myself, "how is this possible? Why wasn't the Amsoil much better?" I'm an Amsoil dealer and I'v been using the product for 5 years, I also recommend this product to my friends and family for racing use. I've been through every section of my Amsoil Business page, and read many of the field tests performed by 3rd parties. I was convinced I was using a superior product, and so are many others.
It may be possible that these samples performed similarly because I have a safe little Toyota, maybe if I had a turbo engine or a high horsepower V8 things would be different. Maybe its because a 6000 mile interval is more stressful to the engine oil than a full year of racing(doubt it). I really have no concrete answer as to the reason these two oils yielded seemingly identical results. Maybe you can share your test results and comment your thoughts on this below....