the engine will reset after about eighty miles of driving.
Is 16 miles enough miles?
I am pretty sure Sir Onyx already explained it: It is NOT based on “miles”
Although there are several variables…. it is based on “number of trips” which is defined by a multitude of very specific conditions. (Cold start, run specific amount of time, Full cooldown, car sits specific time…. etc)
The infamous “loose gascap syndrome” is often quoted by dealership personal who do not fully understand the inner-workings of OBDII diagnostics. It is unfortunate that these folks present themselves as knowledgeable and customers actually believe them. 
If your money-light does not go out after a couple days of driving…. The gascap is not the problem.
Take you car to AUTOPARTS STORE and ask them the “read the codes”. (they will do this for free) Do not forget to write down the codes they get from your car.
Also, it is the job of an autoparts-store to sell auto parts. Try to resist any sales-pitch which they try to sell you something to “fix” your car….. they too, are not very knowledgeable about OBDII diagnostics.
