Starting a car other than one own with your key--- how common is this???

There are only a finite number of key patterns - I forget the stats but in a given area with say 100,000 of a certain manufacturers cars, there's bound to be quite a few that have the same keying.

It was the same with TRW made remotes for cars. One night I go out to the parking lot and hit the button on my transmitter. Both my car (a '93 Tempo) and the Lincoln Town Car next to it unlocked.

On older Saturns, I think there were only 35 theoretically possible key combinations (7 cuts, 5 depths for each cut including no cut at all). Not all of the the theoretical possibilities are used (like no cuts in all positions, are all positions cut the same). I guess that for a 1995 Saturn there are only 25 to 30 different key combinations. Still there are not a lot of possible combinations, so you and your roommate having identical keys is not a miracle, but it is a long shot. I guess you got lucky... Saturn is not much different than the industry as a whole. I think newer Saturns have more combinations (maybe 45 or 50?). As far as I can tell, about the largest number of key combinations for any domestic manufacturer is 60 or so. Japanese manufacturers usually have fewer.

Ed

bianca equ> i own a green 95 saturn,, and oddly enough so does me housemate.

You've got your math messed...

7 cuts, 5 possible depths per cut = 5 to the 7th power = 78125 possible unique keys, a number which includes the "no cuts", all cut to 5, all cut to 4, all cut to... etc. possibilities.

However, there's another factor that comes into play (or at least did for quite a few years): For a long time, on vehicles where the same key is used for both ignition and doors, only about half of the cuts were used for the ignition, while the other half were used for the door/trunk/glovebox/etc locks. Say you had a 7 cut key - only the first three cuts on the key needed to be right to get it to turn in the ignition. The other four cuts on the key were only there for the door locks, but since the ignition lock had no pins/disks in those positions, it didn't matter. Conversely, the door locks had no pins/disks in the cylinder in the positions occupied by the cuts that worked the ignition lock. Some manufacturers used as few as two pins to unlock the ignition, with the others being used for the doors, others used 4 or 5, with only

2 on the "door section" of the key.

Most car locks I've fiddled with were "El-Cheapo" disk locks to begin with (Security level of a disk lock: just about nill - Just enough to keep somebody from opening something if they only made one attempt then gave up and walked away) that anybody with even minimal competence and a bobby-pin and paper clip could pick in under a minute. Chevy was the worst offender, I always thought... Last time I messed with one, it was a 4-disk lock. Quite bluntly, I wouldn't trust a 4-disk lock to keep my dirty underwear secure in the clothes hamper, let alone keep my car from being stolen. Anyway, this particular chevy took me less than 15 seconds to pop. Using two paper clips, in the dark, in a howling blizzard. And was the owner ever grateful... His keys were in the ignition, in the "on" position, on the other side of door he accidentally locked behind him when he got out to hit the men's room at about half past 3 in the AM in a rest-stop on I-75 in the middle of a northern Michigan blizzard. And like so many rest stops along that desolate stretch of highway, vandals had trashed the pay-phone. I had to fill the newspaper rack at this particular rest stop, so he got lucky.

As far as "how likely", that would be a function of how close the two keys are, how many tumblers are used for the lock, and whether they were similar enough to each other to allow a little bit of "jiggling" to turn the cylinder. In theory, with all cuts used by the lock, the number is 1 chance in 78,125. In practice, lots of variables can come together to make the chances *MUCH* higher.

Well there is a chance that it's the same key, but also calculate wear of the locks into the equation.

I've personally experienced 2 ignition locks worn enough that vaguely similiar keys of the same blank started the vehicles. One was durring a summer job in college. I returned from lunch first and needed to move the '78 ford pickup, however co-workers had taken the keys with them. I was driving a '75 ford maverick at the time and used it's key to start the truck and move it.

DUH- You are right - I don't know what I was thinking.

Sorry,

Ed

Yep, five possible levels over 7 positions = 5^7 or 78,125 - not astronomical but still possible that somewhere, sometime it could happen.

There are not many variations and this is quite common.

You actually need to be multiplying - 5 * 5 * 5 * 5 * 5 * 5 * 5 = 78,125

It happened to me.I bought a Blazer to use as a parts truck.While stripping it I figured I would see if the door key was the same and sure as hell,my key opened it.And no it wasnt because the key(s) were worn,both were almost new.

That's wrong!......LOL !

Here's how it works......

For the first cut, you have five depths......

Incorporate the second cut with the first five, and you can repeat the original five cuts in five combinations with the second cut's five depths for 25 unique combinations.

Incorporate the third cut, and you can make 125 unique combinations (the previous 25 cuts using cuts one and two are each used a single time in combination with each of the five cut depths in the third cut.)

so, it actually *does* come down to 5 to the seventh power....or 78,125

For example.....

One cut of five depths offers 5 cuts numbered 1, 2, 3, 4, & 5

Two cuts allow you to use the previous five cuts in 25 unique combinations with the five depths of the second cut - or repeat all of the above five numbers five times with a 1, 2, 3, 4, and 5 in front for cut combinations numbered 1-1, 1-2, 1-3, 1-4, 1-5, 2-1, 2-2, 2-3, 2-4, 2-5, 3-1, 3-2, 3-3,

3-4, 3-5, 4-1, 4-2, 4-3, 4-4, 4-5, and 5-1, 5-2, 5-3, 5-4, 5-5

Three cuts offer five more unique combinations of the previous 25 = 125 or repeat all of the above 25 combinations five times with a 1, 2, 3, 4, and 5 in front for cut combinations numbered, 1-1-1, 1-1-2, 1-1-3, 1-1-4, 1-1-5,

1-2-1, 1-2-2, ......up to 5-5-4, 5-5-5

Four cuts offer five more unique combinations of the previous 125 = 625 or repeat all of the above 125 combinations five times with a 1, 2, 3, 4, and

5 in front for cut combinations numbered, 1-1-1-1, 1-1-1-2, 1-1-1-3, .....up to 5-5-5-4, 5-5-5-5

Five cuts offer five more unique combinations of the previous 625 = 3,125 or cut combinations numbered, 1-1-1-1-1, 1-1-1-1-2, 1-1-1-1-3, .......up to

5-5-5-5-4, 5-5-5-5-5

Six cuts offer five more unique combinations of the previous 3125 = 15,625

Seven cuts offer five more unique combinations of the previous 15,625 =

78,125

OR...

5 cuts X 5 more combinations X 5 more combinations, etc.

5 X 5 X 5 X 5 X 5 X 5 X 5 = 78,125

OR

5 to the seventh power = 78,125

David wrote in article ...

You must be wrong, Woody, because Brent says you can't believe your eyes. Your answer doesn't fit his experience so it must be wrong. Meanwhile, lots of folks are opening doors with keys from other vehicles.