Which is the preferred choice for the 1998 C230?
Would there be any problems switching from one to the other?
I do not know what the previous owner used.

Thank you

Mercedes specifies MB229.5 rated oil for that car. The only such oil I can buy locally is Mobil 1 0W-40. There are others and you can search the web for a list. But that is the only one around here. It goes on sale sometimes. You will need 6 qts and it will take 5.7, assuming you drain from the pan. I don't know how much you need if you use a vac. There should be no problem switching from whatever it has in it.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

A 98 model can use the 229.3 synthetics. In addition to the Mobil 1 both the Castrol and Valvoline are available at many auto parts stores.

http://www.whnet.com/4x4/oil.html