Personally, could never tell the difference, unless the jar was about 6 months old. The mayo always 'stood out' from the immitation at that point.
And with 116 degrees in Baghdad, mayo is probably not the best choice.
Mayo is basically eggs and oil.
We Jews have all kinds of crazy laws about what is and isn't kosher for Passover. Like, "if the Hebrews didn't have it during the exodus from Egypt, it's not kosher."
Well, they had chickens, so therefore they had eggs, and they had oil, because the Bible mentions oil.
So therefore, mayo is kosher for Passover.
Especially when they're knocking off all the ice vendors.