Generally, mixing any brand/grade/base of API licensed lubes (all within the same category) is perfectly fine, if the lubes are mass-market products.
At times, you may be at risk if you are using boutique lubes which have vey specific formulations and then try some other speciality lube in the middle of that OCI. Dave Ward from HPL can talk to this subject deeper, for example. They use some very, very specific additives that, if over or under dosed, can lead to issues. Some additives they use are very sensitive to the right percentage concentration in solution; the anti-foam agents for example. So if you add some other lube or lube-additve to their products, you may risk upsetting the delicate balance of the add-pack. But this is the exception to the rule, and does not apply to most off-the-shelf retail products.
Using broad-based market products are very unlikely to having their chemistry upset, because the add-packs in those products are similar and compatible per the API license category. Don't do things like use a GL-5 gear oil where you need an HDEO, or vice versa, but using one HDEO where another HDEO is already in use is fairly safe.
