I’m not sure if this is the article I was thinking of originally, but it talks a little on it. Basically what I’m asking about is this: if a blend is already using AN then is there less utility in incorporating ester beyond a certain point? Ester does seem to have downsides.
In this sense they’re not necessarily competing chemically with each other directly… it’s more like they are competing for attention from the blender. Is it that with increasing AN usage, there is a decreasing point of optimal ester amount that is most effective in the blend? In other words once you’re using AN, does only so much ester have a benefit?
Polyalphaolefin (PAO) base oil can’t do it alone! Enter Esters and Alkylated Naphthalene (AN). Torco’s high tech base oils for high tech vehicles 100% PAO engine oils must be mixed with other base oils to maximize additive performance. Once upon a time this was accomplished with esters, but...
torcousa.com
Each base oil has its benefits and detractors. I'm not sure I want to bother getting too much into it here, as I've written on it previously, but it's a balancing act and you have to know what you are trying to achieve with the final product.
- PAO has basically no solvency and is hard on seals (it shrinks them), so you have to blend it with something else to get that solvency, be it Group I/II, AN's or esters, and something to offset the seal shrink, which will be esters or AN's. PAO has incredible cold temperature performance, which is why it is often seen in the 0W-xx grades.
- Esters (generally, there are many different types) have high solvency and high polarity along with very good oxidation resistance, heat handling and seal compatibility, making them a good compliment for PAO. However, being polar, as I noted, they tend to compete for surface area with the anti-wear and FM additives, meaning you need higher doses of those compounds to maintain effectiveness.
- AN's have high solvency but low polarity, along with excellent oxidation resistance, high heat handling and seal compatibility. This also makes them a very good compliment to PAO. However, they have low VI's and generally poor cold temperature performance, which means you are limited as to how much you can use when blending a 0W-xx.
So, the idea with Tri-Syn was to capitalize on the strengths of PAO, while balancing its weaknesses with the AN/Ester mix. Using AN to reduce/offset some of the ester content meant better additive response, while the ester content offset some of the cold temperature impact the AN had.
Of course nowadays, with the improved Group III bases, there is less need, if any, for PAO in many of the grades, so you don't need the AN and/or ester content as a mitigation mechanism and you'll possibly just have some included to bump up performance and/or help with additive response (I'm sure there are other things too).
HPL uniquely blends Group III bases, not just PAO, with esters and AN's for their finished oils, depending on which family you are shopping, so getting a Group III based oil doesn't mean you skip out on the benefits of the esters and AN's.