Below are some notable blended HFC mixtures. There exist many more (see list of refrigerants). All R-400 (R-4xx) and R-500 (R-5xx) hydroflurocarbons are blends, as noted above. 1  R-401A is a HCFC zeotropic blend of R-22, R-152a, and R-124. 2  It is designed as a replacement for R-12. R-401A is a HCFC zeotropic blend of R-22, R-152a, and R-124. 2  It is designed as a replacement for R-12. 3  R-404A is a HFC nearly azeotropic  blend of 52 wt.% R-143a, 44 wt.% R-125, and 4 wt.% R-134a. 4  It is designed as a replacement of R-22 and R-502 CFC.
Diesel vehicles may be making a comeback. Diesel engines are more fuel-efficient and have more low-end torque than similar-sized gasoline engines, and diesel fuel contains roughly 10% to 15% more energy than gasoline. So, diesel vehicles can often go about 20% to 35% farther on a gallon of fuel than their gasoline counterparts. Plus, today's diesel vehicles are much improved over diesels of the past.
While that still may be the case for some models, there are plenty of fuel efficient crossovers and SUVs available in todayâs marketplace, some of which get over 30 MPG on the highway. Compared to last yearâs Top 10 list, fuel economy has gone up across the board. Just a year ago the most fuel efficient SUVs had a worst combined MPG rating of 25 while the best vehicle saw 30 MPG combined. This year, the most fuel efficient model stickers for 31 MPG combined while even models at the bottom of the list are posting a 2 MPG improvement to 27 MPG. So if youâre in the market for a fuel efficient crossover or SUV then youâve come to the right place. Weâve listed the Top 10 most efficient models, based on their combined city/highway rating.