My car key started my friend's car and I was wondering how that is
possible?  They are both manufactured by Jeep, but different models
and both are 1998.  Is this unusual; what are the chances?

Dear reifmn-ga;

Thank you for allowing me to answer your interesting question.

?What are the chances??

Well, according to STRAIGHT DOPE there are 100,000 different
possibilities to GM keys and about 5000 different possibilities to
both Ford and Chrysler keys (Jeep is a Chrysler product). Speaking
broadly then, since one key design is theoretically duplicated only
once in every 5000 cuts, your chances of having the same Jeep ignition
key as someone else is roughly 5000:1 (or one in 5000, however you
prefer to look at it).

Obviously these chances can differ based on other variables and they
do not take into account the possibility that a DIFFERENT key, for
some unknown reason, might also function in your friends ignition, but
generally speaking this 5000 to 1 ratio would be the manufacturer?s
perception of how likely you are to have been issued a IDENTICAL key.

STRAIGHT DOPE
http://www.straightdope.com/mailbag/mcarkey.html


I hope you find that my research exceeds your expectations. If you
have any questions about my research please post a clarification
request prior to rating the answer. Otherwise I welcome your rating
and your final comments and I look forward to working with you again
in the near future. Thank you for bringing your question to us.

Best regards;
Tutuzdad-ga ? Google Answers Researcher



INFORMATION SOURCES

STRAIGHT DOPE
http://www.straightdope.com/mailbag/mcarkey.html


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"Different possibilities" keys Chrysler

"Different keys" Chrysler

I don't know about Jeeps, but many car manufacturers have relatively
few different key designs. A few years ago, in a big parking lot, I
accidentally got into someone else's car that resembled mine and was
able to start the car with my key. I might have driven off in the car
if I hadn't noticed some kids' toys in the backseat that I knew didn't
belong to me.

Here's a similar account:

http://archives.dakota-truck.net/0108/0544.html

I found that locksmiths use a set of 64 keys and 4 tools that will
open doors and operate ignintions on all 1989-1999 Chrysler/Jeep/Eagle
vehicles.

TRY-OUT KEYS
http://members.aol.com/leedobbs/try-outkeys/disc.html

reifman-ga  Once again, as usual, Pinky has it right. There was a
time, admittedly long ago, that GM and specifically Chevy keys had
only a few differences. A friend who accidentally locked his keys in a
Chevy at a gas station was soon able to use a stranger's Chevy key to
unlock the door.