A new series of nonionic surfactants with double hydrocarbon tails and a single polyoxyethylene (POE) chain 1,3-dialkyl glyceryl ether ethoxylates with an alkyl length between diC8 and diC12 and ethylene oxide (EO) number between 3.9 and 25.6 were synthesized and characterized. The correlation of their surfactant–polymer (SP) flooding behavior with the alkyl length and EO number were studied. Although the individual surfactants can be made highly surface-active by matching the alkyl lengths with an appropriate EO number as reflected by the low critical concentration range of 6 × 10–7 to 9 × 10–5 mol/L and γcmc as low as 26.5–30.5 mN/m at 25 °C, they are not good surfactants for SP flooding when used alone since ultralow interfacial tension (IFT) between Daqing crude oil and connate water can only be achieved by a few members with short POE chains or hydrophile–lipophile balance (HLB) numbers near 7–8, which are poorly soluble in water. However, those with long POE chains exhibit excellent synergism in red...