Well, there are ( or were ) various other combinations since the different characters in the 4 letter code have specific meanings

The 1st character seems to be the class of Car, which in the UK is in a sort of ascending order

Group A (Mini)= M (Mini 1.1)
Group B,Q (Economy)= E (Ford Fiesta 1.25)
Group C,E (Compact)= C (Ford Focus 1.6)
Group D,F (Intermediate) = I (Ford Mondeo 1.8 LX)
Group X,Y (Standard) = S (Ford Mondeo 2.0 Ghia)
Group V,T,M (Full Size) = F (Chrysler PT Cruiser)
Group G,J,I6,U6 (Premium) = P (Vauxhall Omega 2.2 CDX)
Group H,A6,B6,T6 (Luxury) = L (Mercedes E240)
Groups S6,L,E6,F6 (Special) = X (Mercedes S320L)

The second character denotes the tyoe of vehicle.
C,D,S,X = Car
F = 4 Wheel Drive
W = Wagon
V = Van
T = Convertible

The 3rd character indicates transmission type
M = Manual
A = Automatic

The 4th character indicates whether it has air conditioning
R = Air Conditioning
N = No Air Conditioning

A compact car with Manual transmission and no airconditioning would be CCMN for example whilst a standard manual convertible with air conditioning would be STMR. The UK list of vehicles is on http://www.hertz.co.uk/byr/fleet/index.cfm .

and the classifications currently are

MCMN, ECMN, ECAN, CDMR, CCAR, IDMR, IDAR, SDMR, FDAR, PDAR, LDAR, XDAR, XFAR, STMN, FVMR, FVAR, IWMR, PWAR, PSAR, PTAR, LXAR, LCAR, LWAR, XWAR, XCAR

Dave

[This message has been edited by Dave Noble (edited 09-28-2002).]