I want to install a utility sink in my garage, which will require approx a 30 ft run of 11/2 " drain pipe.
The 11/2" will be going into the 3" main drain line. I should be able to get 1/4" per foot pitch over the 30 ft run.
My guestion is ,will I need to install a studor vent at the sink trap?

All sink traps need vents and an AAV works in most situations but may not be code in your area. You could run a vent stack up to above the garage roof. If this job is "off the books" with no permit you can try a STUDOR but it may come back to bite you if/when you sell or get caught.

If your local plumbing code allows it, some don't. If you opt for the Studor, make sure you follow the instructions as they will tell you how far above the trap, below the rim etc it needs to be installed. I have 2 of them in my house, a 7 year old log home, and they have been faultfree.

Hi,

You may run a studor vent as long as it is roughed in as high as u can or run the vent at least 10 ft high minimum but outside of garage opposite side of garage sink. Basically your drain and vent would be exposed on other side would be an option. You do not have to penetrate roof.
Make sure 1.5" tee drain to receive discharge from sink is verical and studor is high if installing under sink.