I have always doubled fried, my French Fries. The first fry is the important one, this is where you are actually cooking the potato. This is also the lower heat fry. I fry mine at 325° for about 5 to 6 minutes, or until they start to change to a yellowy, light golden color. Remove them from the oil, increase the oil temperature to 375°-390° and place fries back into the oil for 1-2 minutes, until they turn golden brown. Remove salt immediately after removing from the oil.
Also, I use either canola, or vegetable oils, sometimes a mixture of the 2. You have to watch what oils you are using, because the flash points are different. If you are using a mixture of 2 or more make sure you do the math and find what the new flash point will be. If not you could be look at some very serious problems.
Brinkmann Trailmaster Limited
Brinkmann Vertical Charcoal Smoker
Weber Spirit E-320 Propane
Weber One-Touch Silver 22-1/2"
Weber Jumbo Joe 18"
Weber Smokey Joe Gold 14"
Fully Functional UDS 22.5" Dual Layer