have a 2004 GS300 with 48,800 miles - dealer says i should change the timing belt.

Although timing belt changes vary from 60,000 to 105,000 miles on most vehicles, yours is over 10 years old so I think the dealer is giving you very good advise. Get the timing belt changed cause if it breaks it will be VERY costly.

Yep its time to change you belt, Please hit my helpful link if this gave you some help ..

It’s not Only mileage,it’s Pollution ,the air and the fumes eat that Timing belt material,Change it,If it goes,Your engine will open and close valves out of time,or when the pistons are in the wrong Stoke i.e.: Bent Valves,Holes in Pistons,Cam Lobe Problems,if it happens your probably better off buying a Rebuilt Engine then Fixing Everything,And a 2004 with 40k some miles is worth 10 to 15K depending on condition and Options.Don’t Take a Chance,Different Engine Then numbers won’t Match! Do it ASAP!