Should we generally use float literals for floats instead of the simpler double literals?

Question

In C++ _{(or maybe only our compilers VC8 and VC10)} 3.14 is a double literal and 3.14f is a float literal.

Now I have a colleague

Answer 1

There is a difference: If you use a double constant and multiply it with a float variable, the variable is converted into double first, the calculation is done in double, and then the result is converted into float. While precision isn't really a problem here, this might lead to confusion.