Either one of those is a bit of overkill to control Spider Mites or Thrips. If mixing them would be better then spraying each the people that manufacture those products would have already, never, ever mix 2 products without digging into what would happen if you did because some things could cancel the benefits of each other out while others could produce a very hazardous material.
Spider Mites can be controlled very easily with applications of an Insecticidal Soap as well as increasing the humidity around the plant(s). Thrips can be easily controlled with Insecticidal Soaps as well.

ryan7662,

The biggest problem with oils, is getting them into a decent suspension...oil as a rule of thumb is like "oil", does not blend well with water. A lot of "summer oils" get around this by adding something to aid the oil so it does mix/blend well with water..they add an emulsifier, to help keep it in suspension better than just relying on agitation alone...ITEM 1.

For Thrips,Spinosad is still about the BEST product out there (newer chemicals are getting there, but may not be easy for you to obtain). Getting the product to the pest is normally the biggest problem (as with Thrips, they get into/hide in areas of the plant that it is hard to get the pesticide "into") and sometimes a tank mix, that reduces surface tension of your spray water (say insect. soap), would allow the Spinosad to get too the pests better..ITEM 2.

Your best bet is a combination of soap and Spinosad (unless you know for sure the " einstein oil" has an emulsifier or something that may reduce water surface tension). If the pest get's by the first line kill of the soap, the Spinosad will give you a bit more activity/longevity on the plant.

Schmoo

I mix them when necessary to combat pests and fungal disease. I use this combo on all sorts of vegetables and have excellent results. As I live in the hot south I use a gallon size pressure sprayer after the sun is off the garden in the early evening.

Neem and spinosad are showing promise against
most of the major defoliating insects.

Overusing most miticides and such is a surefire way for those pests to become tolerant .

A few days ago I sprayed neem oil thr my pressure spray. Today I mixed spinosad in the bottle but never cleaned it out. there wasn’t any neem oil in the bottle just didn’t rinse it out. Would that offset the spinosad? Also, I used 2 gallons to spray a lot of plants. One website said never spray more than 3 gallons in 1000 square foot area. My garden isn’t 1000 square feet but I have a lot of plants compacted in a med size area. I hope it wasn’t too much?