25K Mile UOA Results

Results from my mid-10K oil check @ 25K miles, including all the prior UOA results below. All on Mobil1 0W-20 since the first change, regular Toyota oil filters up to 10K miles, then TRD oil filters since.

 

Iron and aluminum are primary engine materials, along with chromium that hardens steel. Low levels mean low wear in the engine.

Tin and copper are used in engine bearings, so low levels of these metals mean bearings are in hood shape.

In other threads, concern had been expressed about relatively high silicon levels in new engines (possibly from casting sand residues). That's one reason I changed my oil early the first time. Note that Si levels went down 4x by the second oil change, and had gone down by nearly 10x at 10k miles. Si is not good in an engine.

One important parameter is TBN, which measures the amount of additives in the oil. Mobil 1 0W-20 has a TBN of 9.8 out of the bottle, and a level of 1.0 or less means the oil is worn out. Mobil 1 will go more than 10k miles in a Prius.

I'll do the UOA @ 30k miles, then at 10k intervals.