So this is one complaint I actually have in regards to Mcdonald's fries that I eventually caught on to when I was about 10/11, and why I didn't like them as much for a good while.
As an adult I have grown to like them again, but honestly my only complaint is the texture with them feels inconsistent. Some fries have a nice, soft crunch to them while others just taste a bit chewy. Not the best feeling when you munch away on those greasy, salty fries.
If fries taste unusually greasy, it’s time to change the oil.
I worked at a place called Zinburger. (High end burger joint). We cut our own fries (never frozen), and zucchini fries and sweet potato fries too.
With all the fries, you had to change the oil several times a day. Oil has to be 375 degrees for French fries. Any lower temperature, the fries absorb the oil, and you get a mushy greaseball mess.
The temperature drops when the oil starts getting dirty. Fryers have a skimmer to take out burnt fries, onion rings, etc.
At the end of the night, the oil is drained, and the bottom of the fryer is cleaned out of all the sludge that builds up.
It’s like changing the oil in your car. Every 3,000 miles you have to change the oil and all the gunk that builds up.