need to know
 

I recently purchased a 1998 S500 and am in need of an oil change . Can some one tell me what viscosity oil to use? is it 5W-30? The car also has a vibration that comes and goes in the steering is there a common problem in these models ?

Use Mobil 1 0W-40. The vibration may be a bent rim.

Hey you're from Minnesota. Cool, or cold I should say.

What's the owner's manual say in regards to oil? Usually a good guideline.

Take the car into a Midas or similar rip off front end place, for a free estimate. The mechanic will tell you everything is wrong with the front end. Then look him in the eye and ask what really needs to get fixed, for safety reasons. Ask him to show you. You will find out more about your front end than you knew before. Don't hesitate to get a second opinion. They are free, after all.