Final answer:
When taking fuel samples, there is not a specific amount of fuel that needs to be drained; just enough to get a clear sample for testing, which is usually a few ounces.
Step-by-step explanation:
The question is how much fuel one should drain when taking fuel samples. Normally, this does not pertain to a specific quantity since the intention is to obtain a representative sample of the fuel to test for contaminants such as water and debris. However, various sources generally advise draining a small amount, just enough to fill a tester — often around a few ounces or whatever is necessary to get a clear sample without contaminants that might be sitting in the bottom of the tank or the fuel line.
For example, one might only need to drain the fuel until the sample appears free of water or debris. When taking fuel samples, initially you would drain a small amount of fuel for testing purposes. The amount of fuel drained may vary depending on the purpose of the sampling, but it is typically a small quantity, such as a few milliliters or ounces.