I worked at McDonalds long ago, and I am a huge fan. If you are interested in understanding why they are so incredible, make sure to read "Grinding It Out" which is the story of McDonalds told by Ray Croc, who turned a small local store into one of the greatest franchises the world has ever known. He was in his mid-50s when he stated, and the whole thing is just inspiring for entrepreneurs no matter how many time you might have failed before. But I digress...

The thing about working at McDonalds is that you learn exactly what everything tastes like - and you notice all the little changes. For example, the difference in quality between a quarter pound patty used in the quarter pounder and double quarter pounder, and a "10" (1/10 pound) patty used in the regular cheeseburger and double-cheeseburger. I have eaten everything on the McDonalds menu, and can tell you what the most disgustingly unhealthy thing by caloric density is (not the fries!).

So, the most important factor we noticed about the french fries was how old the fry grease was. Each night 1 of three things happen to the fry grease:'

1) it is skimmed for any remnants of fries and left to simmer at a low warm temperature for the next day

2) it is run through a cleaning machine (2-3 times per week)

3) it is completely replaced by a technician (every 1 or 2 weeks depending on time of year)

New grease is very clear, like fresh motor oil you put into your car. As the grease gets older turns more and more golden brown as it gets more carbon in it from little bits of fries that break off and burn in the hot oil and disintegrate. Eventually, right before it is replaced, the grease is very brown and the fries will actually come out with tiny brownish bits on them. Some people really liked the "dirty grease fries" but the majority of staff knew when the best french fries were made - when the grease was about 4 days old, right after the first cleaning. I can't tell you exactly why, but these fries were the yummiest to the point where I would only eat them at this point (gotta stay thin somehow working there!) and crew members would bring in their kids on that day to eat.

Its also important to know that fries are never ever cooked in the same grease used for chicken nuggets, fish filets, etc. I'd be curious to know what that tastes like if anyone has every broken the rules and tried it, but that was a religious issue at the McDonalds locations I worked at so we never did.

Anyway, if you're curious and have a regular McDonalds you can always ask them when the last time the grease was cleaned or changed.