Cost of operating a Skyhawk

Not possible without knowing how many hours per year you will fly

It's perfectly possible. The only one of the variables he listed that
changes with the total number of hours flown will be normal maintenence.

You can figure about 8 gph. You'll need to find out what gas costs
where you fly the most. Most 172's run great on mogas and this can save
a lot. You will need 87 octane minimum and no alcohol in the gas. Oil
will depend on the engine. The Lycs burn less than the Continentals as
a general rule. I use Phillips XC 20W-50 and it costs $23 per case and
I use 9 quarts in my 182. I think the typical 172 will use 7 quarts.
So you're looking at $13.41 per oil change plus a filter if you need
one. I don't use an oil filter but last I saw they were about $12 each.
A typical O-320 overhaul will run about $13-15K with a 2000 hour TBO.
So figure $7.50 per hour for your engine overhaul. Add another 25
cents per hour for your prop. Annual maintenence will vary widely
because shop rates vary widely. I can spend $42 per hour up to $70 per
hour around here. A 172 is pretty cheap to operate. For a single owner
with a fresh PPL and a $50,000 hull value will run you about $600-700
per year for insurance. Tiedown and hangar rates vary even more than
shop rates.