How do I check if I have bad fuel in my car?

A fuel test procedure and kit (without sending out to a lab) involves 3 steps.

1. The first involves lowering a probe to the bottom of the tank with a paste that changes color if it touches moisture. The probe almost resembles a bicycle cable in a clear sheathe. This requires the probe and the color changing paste.
2. The second involves retrieving a sample of the gasoline. Place the gasoline in a graduated cylinder. Add some amount of windshield washer fluid. Cork the sample and shake the tube. Wait until it settles. Compare how much gasoline you put in to how much is left after everything settles. This shows how much alcohol is in the fuel. It should be no more than 10%. All this test needs is a graduated cylinder that can survive gasoline. This is the easiest thing to acquire.
3. The third involves retrieving a sample of the gasoline. This tests the volatility of the gas known as Ried Vaper Pressure and requires another special testing tool. Chill the gasoline and tool on ice for 30 min. Pour the fuel into the tool and close it. Place the tool into hot water for 10 min and measure the water temperature. Read the pressure from the gauge on the tool. Compare the pressure and temperature to a table that comes with the tool.

Only #2 can be done without super special tools.