This study is focused on the reduction of CO2 emissions and costs associated with ultra-low viscosity (ULV) engine oils for passenger vehicles. Specifically, the reduction in life cycle CO2 (LCCO2) emissions from lower-viscosity engine oil and the oil drain interval (ODI) extension were estimated taking into account both mineral engine oil and synthetic engine oil. Furthermore, the cost-effectiveness of ULV engine oils were investigated by performing base-stock cost analysis. When the volatility limit of the Noack test (American Society for testing and materials (ASTM) D5800) was set to 15 wt %, the results indicated that the lower limit of kinematic viscosity at 100 °C (KV100) for mineral engine oil (with Group-III base-stock) and synthetic engine oil (with polyalphaolefin (PAO) base-stock) were approximately 5.3 and 4.5 mm2/s, respectively. Compared to conventional 0W-16 mineral engine oil (KV100 6.2 mm2/s), the effect of reducing LCCO2 emissions on ULV mineral engine oil (ULV-Mineral, KV100 5.3 mm2/s) was estimated at 0.6%, considering 1.5–1.8 L gasoline engines in New European Driving Cycles (NEDC) mode. ULV-Mineral, which continues to use a mineral base-stock, is considered highly cost-effective since its cost is similar to the conventional 0W-16 mineral engine oil. On the other hand, compared with ULV-Mineral, the vehicle fuel efficiency improvement from the use of ULV synthetic engine oil (ULV-PAO, KV100 4.5 mm2/s) was estimated to be 0.5%. However, considering CO2 emissions during engine oil production, the reduction of LCCO2 emission from ULV-PAO compared with ULV-Mineral was estimated to be only 0.1% or less using 2030 standards (assuming a vehicle fuel efficiency of 66.5 g-CO2/km) when ODI is set equivalent (7500 km) to mineral engine oil. As a result, ULV-PAO’s cost-effectiveness, considering the cost increase of PAO base-stock, was found to be nominal. Contrariwise, when the characteristics of PAO base-stock with higher oxidation stability are used comparatively with the mineral base-stock while extending the ODI to 15,000 km, the effect of reducing LCCO2 emissions of ULV-PAO was estimated to be 0.7% in 2030, making ULV-PAO a competitive and cost-effective alternative. In other words, the popularization of synthetic engine oil toward 2030 will require the consideration of both viscosity reduction and ODI extension.

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The effect of suction flow on the mass transfer coefficient of tubular ultrafiltration membranes, in particular that under a high-flux condition, was studied. We pointed out that N Sh is proportional to N Re 0:875 N Sc 0:25 under turbulent conditions, and that the proportional constant, b, exceeds 0.023 when the effect of suction flow is not negligible. We conducted the velocity variation method using ultrafiltration membranes with MWCOs of 20k and 100k and dextrans having molecular weights of 40,000 and 70,000 at the conditions, where N Re exceeded 3:6310 3. We demonstrated that the effect of suction flow includes not only flux but also the diffusion coefficient of solute, and that the ratio of the flux to the diffusion coefficient, expressed as N Pe w , is an important index. Finally, we concluded that b50:023, when N Pe w is smaller than 2:23310 3 , giving the Deissler equation itself, and that b52:04310 26 3N 1:21 Pe w , when N Pe w exceeds 2:23310 3 .

This paper presents a comprehensive life-cycle analysis of CO2(LCCO2) emissions from automobiles using a hybrid life-cycle inventory approach to predict the growth of electrified vehicles in Japan. Herein, the hybrid electric vehicle (HEV), plug-in HEV (PHEV), and battery electric vehicle (BEV) versions of the mass-produced Toyota Prius hatchback are analyzed, considering the automobile-usage environment in Japan. In particular, a breakeven analysis of HEV vs. PHEV vs. BEV is conducted in terms of LCCO2emissions that are affected by (i) outside air temperature and (ii) CO2emissions during power generation from the present day up to 2030. Our results show that HEV has the lowest LCCO2emissions when the current thermal-power-dependent electricity generation mix (average for 2012–2014) is considered, followed in order by PHEV and BEV. However, it is predicted that in 2030, PHEV will have the lowest LCCO2emissions, followed in order by HEV and BEV, as it is anticipated that nuclear and renewable energy sources will be widely available by 2030. PHEV is expected to gain popularity by 2030. Regarding BEV, large quantities of CO2emissions are emitted during battery production. Furthermore, due to the domestic electricity generation mix from the present day up to 2030, the LCCO2emissions of BEV will exceed those of HEV and PHEV.