This was a recent post that I came across on the Exxon Mobil Industrial forum. Someone posted this question: Why Engine Oil is made by group 1 base or group 2 oil. Why is not made by group 3 base oil. This was the response from Korey Sargent, an engineer in training at Exxon Mobil: To my knowledge, there are products on the market which utilize group 3 base stocks. There is a common misconception that higher base stock group numbers automatically lead to higher quality engine oil - this is simply not true. While the base stock does have some bearing on the final product performance, it does not necessarily mean the product will be superior. There are many other factors in an oil formulation which contribute to a good overall product and a lot of this comes down to additive chemistry. I suggest selecting products based on performance related attributes like OEM approvals, API specifications, proof of performance claims, warranties, customer reviews, etc. These factors are a better indicator of the final product performance. ~ Then, afterwards, some other random person posted this: As we go higher in base oil groups, solubility of base oil drops and in engine oils, we have to add between 20-30% of additives. In this case additives will not dissolve properly. Many companies in north america are blending synthetic blends with group 1&2 with group 3 or PAO to make a fully formulated product. Another reason, is it does not remain cost effective as you are already making PAO based oils. There will be no big difference in cost so it will become tough selling option.