Jaijui:

Potatoes brown not because of the oil while frying but because of the sugar in it. But frying it in a lot of oil, adds a pleasureable taste .  Please read the following which I got from the Internet. 

"Potatoes "brown" when sugars in the potatoes caramelize. Some potatoes have far more sugar/solids than others, and storage conditions and pre-processing methods make a big difference in the degree and consistency of browning you will get. Generally, I recommend russet Burbank potatoes for frying, and I suggest blanching for 1 minute and shocking in ice water, after peeling and cubing, to prepare the surface of the cubes for frying with minimum soak up of oil. To initiate carmelization without burning, you'll do better to stay away from teflon pans, and use (at a minimum) several tablespoons of a stable vegetable oil (enough to coat the bottom of the pan evenly, with a little more for the potatoes to soak up, because, well, they will anyway). Wesson oil, peanut oil, safflower oil, or other cooking oils that can take temperatures up to 390 degrees Fahrenheit are needed. Olive oil will generally smoke at lower temperatures (375 degrees F) than you need to reliably caramelize potatoes. You need to bring the oil in the pan up to at least 360 degrees Fahrenheit before adding potatoes. And you need to not add so many potatoes at a time that your pan temperature drops well below your frying temperature, as this will just cause the potatoes to soak up more oil, and inhibit the browning process. If you are working with a normal electric range, a cast iron skillet may be your best bet, because of its higher weight and latent heat. Get the oil hot, and keep it hot, and your potatoes will brown, if they have enough sugar."

Regards. 
Rajaputhran.