How much will I spend in fuel?

I'm 16 and I'm thinking about buying a 1999 Ford Explorer XLT as my first car. I'm also thinking about going to college 3 hours away. I will have to make occasional trips home for breaks. I'm just curious how much I'll spend on gas. How often will I have to stop to get gas? I don't want to find a different car. I'm paying for the car and gas myself.

The amount of gas used and the cost is directly related to the miles you cover, the cars capabilities and the way you drive. From the info you give this is impossible to work out.

No one can tell you. As Timbo already pointed out to you, there's a direct correlation between total fuel consumption and distance traveled.

But two large factors will be how you drive the vehicle and what type of shape it is in. If you drive the vehicle at higher rate of speed and/or the vehicle is out of tune, that can increase your total fuel bill significantly.

Lastly, lets not forget the ever fluctuating cost of the fuel. When the price at the pump increases, so do your fuel bill.

Considering the car is in good condition and is the 4WD model, it will give about 16 combined mpg. And considering that your college, which is 3 hours away, assume it is about 200 miles one way distance. And finally, assuming that you drive at a fairly decent rate of acceleration and cruise on the highway within the speed limit, and basically overall drive like a decent citizen, you be looking at consuming about 12 gallons of gas just for going one way from home to college or college to home. Making one more assumption that the average price of 87 octane gas is about $3.75, that is $45 spent only on gas for going one way. Considering any Slight error in calculation, just assume it will cost you $50 for a one way trip, and so $100 for a round trip. If you think you tend to drive a little on the faster side on the highway, or if gas prices are cheaper or more expensive in your area, then make an adjustment to my train of thought above.

You should get approximately 20 mpg on the open road so to drive 3 hours @ 60 mph = 180 miles you should burn 9.0 gallons of fuel. At the current average of $3.50 p/gal the trip should cost approximately $31.50 each way.