In a mixing bowl combine the lukewarm water with a tablespoon of sugar and yeast. Let it sit until the yeast bubbles.
Add oil and whisk in 4 eggs. Add in the remainder of the sugar and salt. Slowly stir in flour one cup at a time.
Add the dough hook to your mixer and knead until the dough is formed into a ball and elastic. You can also do this step by hand. The dough should not be sticky. If the dough is still sticky and wet, you can add more flour until it holds its shape.
Place the kneaded dough into a large oiled bowl. Cover it with a towel and let it rise for an hour.
Punch down the dough and let it rise for 30 more minutes.
To form a four-piece braided challah, divide the dough into 8 pieces, this will give you two loaves of bread. Roll each piece of dough into a long rope.
Place 4 pieces lined up next to each other and seal the ends together. Start forming it into a braid but working with 4 pieces. Seal the end and tuck it under -- this way it will hold the shape. Repeat with the other four strings of dough to make a second loaf.
Place the challah loaves on a baking sheet and let them rise for 30 minutes. Meanwhile, preheat the oven to 375°F.
Whisk the egg and brush the top of the challah.
Bake at 375°F for 30 to 40 minutes, depending on the size of challah. Fully baked challah should be golden on the outside.