Final answer:
It is possible to mix full synthetic oil with a synthetic blend, but this may not give you the full performance advantages of a full synthetic oil.
Step-by-step explanation:
Yes, you can mix full synthetic oil with a synthetic blend; however, it is important to keep in mind the manufacturer's recommendations and warranty conditions for your vehicle. Both types of oils are compatible since they contain some synthetic base.
A synthetic blend is essentially a mixture of synthetic base oil and conventional mineral oil, so adding full synthetic oil will simply increase the proportion of synthetic oil in the mixture. Keep in mind that you may not fully benefit from the performance advantage of full synthetic oil when mixed with a synthetic blend.