Guess that brings us back to the old claim:

The Jargon Dictionary entry:
http://info.astrian.net/jargon/terms..._may_vary.html

Your mileage may vary
Your mileage may vary cav. [from the standard disclaimer attached to EPA mileage ratings by American car manufacturers] 1. A ritual warning often found in Unix freeware distributions. Translates roughly as "Hey, I tried to write this portably, but who knows what'll happen on your system?" 2. More generally, a qualifier attached to advice. "I find that sending flowers works well, but your mileage may vary."