For a particular car, kbb.com provides a trade-in value of $4800 and edmunds.com says $5600. That's a heck of a spread. Which guide do car dealerships usually use - one of these or something else? nadaguides.com doesn't provide a trade-in value as far as I can see.

Thanks,
Sixto
95 S420
91 300SE
87 300SDL
83 300SD