Older adhesives are dissolved in a mixture resembling paint thinner. The newest adhesives do not depend on the evaporation of a solvent and can be hard to remove.
I would start with the paint thinner, then 3M adhisive remover, D-Limone (pure concentrated orange cleaner) opps, goo-off, "Latex paint remover", 3m 5200 remover and finally chill it and scrape it off.
Amen to that
Taking adhesive off old beaters is a cinch compared to what I ran into on our "new to us" van. Letters are eight years young and some dandy adhesive indeed. Acetone (my personal favorite) will do nothing more than spread it over a larger area
guess I'll spring for 3M product next.