I think the only reason they make a blend is for people who don't want to spend 4.50+ a qt for full synthetic. Synthetic oils and gear lubes are the best protection you can put in your tractor or vehicle. A conventional oil will do the job, just not as well. I would not purchase a blend-if you want to use a synthetic lubricant pay the extra money and purchase the extra protection. Go to Amsoil's or Mobil 1's web sites and learn about synthetic advantages. In a semi, rearends and trans will usually run 20 degrees cooler with a synthetic gear oil. If you have to tear a synthetic filled component down for some reason, you can't believe how clean the gears are compared to conventional lubes. Semi truck trans and rearends are warranted for 5year/500,000 mile warranty when synthetics are used vs. 2year/200,000 mile with conventional oil. You will see more and more manufacturers with factory fills of synthetic lubes.