On a 135,000 mile car. How bad would a small shot (50 - 100) of nitrous be to the motor, if used once in a while?

 

How is the tune on your motor?
Do you have a bigger fuel pump?
Do you have a wot switch?

If no to any questions, don't use nitrous

 

As long as the car runs good and is mechanically sound it won't really hurt it. I installed a 150shot on a stock mustang with like a 130,000 miles and tha was like two years. that thing still runs. The 5.0 has a forged piston most of the years so he was allowed to run a bigger shot but 50-100 is def. possible.I would recommend a bigger fuel pump but def. go with a wet kit so that you don't have any problems with leaning out. Most nitrous companies are conservative with there fuel jetting to help out. When i had my car dyno'd i went down two jet sizes for a good air fuel ratio.