15k services are pretty subjective but, should be a lube service (7500 mile service) plus air filter(s) change, tire rotation, wiper insert and dust filter if not done on the 30k's.
30k service is all the filters (your car has the 722.6 trans, service it every 60k), plus the 7500 and plugs. Check the caps and rotors on a EZL car. (your should be dis)
At 90k the diff oil is changed and I recomend the activated charcoal filters if you use them. (which are pretty nice when pine pollen season rolls around)
All services get the battery water level checked, latchs, door checks and hinges lubed, sunroof tracks cleaned and lubed, air pressure set (including spare), diff oil level checked and ATM level checked. Of course the obvious, oil and filter change. The power ant mast wiped with light lube and all lights checked. Brake condition checked, suspension components, flex disc's and basic systems function tested.
Naturally, the coolant and brake fluid is changed at the recomended intervals as well as the service books filled out and stamped.
On a car with a 7500 mile service interval I wouldn't have changed it to synth but, being that it already is on synth, I'd leave it on it.
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.