This was super easy using a food processor, or I'm sure a blender or mixer would work.
1 T Dijon mustard (optional)
1 T rice wine vinegar or lemon juice
1/2 C Canola Oil
1/2 C Olive Oil (I did all olive oil)
salt and pepper to taste
Using your blender, processor or hand mixer, mix well the first 3 ingredients with 1 Tbls of oil. VERY SLOWLY (I used the oil reservoir on my food processor) add the rest of the oil till well blended. Add seasonings to taste and refrigerate. It should last about a week or so, they say. I've had mine longer than that and it's still fine.
That's it! It's so much healthier to make it yourself, as you can pronounce all the ingredients!