AbstractThrough co‐oligomerisation of alphaolefins with alkylmethacrylates, fluids are obtained with a unique chemical combination of non‐polar PAO and polar ester oil in one molecule. The polarity of these co‐oligomers between P A 0 on the one hand and ester oil on the other helps to avoid the typical disadvantages of these common synthetic base oils. Thus, co‐oligomers offer superior solvency for DI packages, neutral elastomer behaviour, the hydrolytic stability of sterically hindered esters, a thermal and oxidative stability close to PAO, and free miscibility with mineral oil and synthetic base stocks. Co‐oligomers are Newtonian fluids of high purity and with a viscosity range between 50 and 600 mm2/s at 100°C. Both viscosity level and purity open up a range of applications. Even without high molecular weight VI improver, gear oils, and hydraulic oils with outstanding viscometric performance can be formulated. The purity has a positive influence on properties such as demulsibility, de‐aeration, and foaming behaviour. The present paper compares co‐oligomers with common base fluids and gives examples of typica