Hi,
I am planning to use an MQ3 to detect alcohol. The problem is that I need to know when I have Methanol and when I have Ethanol.
Has anyone ever been able to tell the difference with the sensor?
That is not possible 
The MQ3 sensor detects "something" and changes its resistance. It sensitive more or less for a number of gasses. That's all.
Brewing beer in your basement ? Making moonshine ? You need professional equipment or you will risk the health of yourself and others.
(not very serious)
I: take a sample. set it on fire. (flames are differest)
II: ..sample. rub it in your hands. see foam? -> dont drink it.
(this is common test for imported, cheap, alcohol)
The two are chemically very similar (just a CH2 group difference) which makes them hard to distinguish.
Gas chromatography will be able to tell them apart easily. IR spectroscopy may do as well, I would expect to see a different C-O resonance frequency.