Originally Posted By: Curtis Newton
Originally Posted By: HKPolice
Originally Posted By: KingCake
50/50 is the worst way to make a blend. You should either have a majority of conventional or a majority of synthetic.
This is the only correct post here. Mixing your own oil is never a good idea because you don't know how the different additives will react with each other. Off the shelf semi synthetic oils are made from scratch using additives tailored for a mixed base stock.
For example: Group2 base stock has a lower VI than Group3, so a conventional oil will need more VII than a synthetic oil to reach 5w30 grade.
If you mix conventional 5w30 with synthetic 5w30 then the final grade could be more like a 10w40 because the extra VII from the dino oil will thicken up the synthetic base stock.
Sure, the homebrew mix will work fine but it'll be inferior to off the shelf semi synthetics with an unpredictable viscosity.
I intend to take another sample at 215k, but according to Blackstone the homebrew mix at the 155k oil change looks pretty good (see below). Viscosity looks about right.
I break all of the rules in that I change my oil filter every other change, use a Fumoto valve, mix my own oil and add in 4oz of Tufoil.
As a side note, the early couple of changes were Mobil 1.
This is easy to explain:
1) UOA is from an ES330 with 3MZ-FE engine, 1 of the lowest stressed engines made by Toyota.
2) Interval was only 5K, any oil can survive that with flying colors, even bulk generic dino.
3) Mixing PP & PYB is one of the most predictable brews because they're the same brand and use the same type of additives (Calcium). If you mix different brands with different add packs, the end result won't be so favorable when pushing the limits (10K+ miles).
I think your UOA actually looks pretty bad because the TBN is already low @ 2.3 after only 5K miles. Most off the shelf blends won't reach that level until 7-8K. Also, it has technically sheared out of grade. The minimum for SAE 30 weight is 9.3cST, this oil is already at 9.12cST after only 5K miles.
So in summary, yes you broke the rules but wear numbers still look normal due to the short interval & easy on oil engine. Still, this mix doesn't look any better than off the shelf blends due to poor TBN retention & high shear rate.
