I just got my first b-service on my 99-clk 430 this past week...i saw on the sheet of paper they gave me that they put in castrol oil...i was wondering if that is synthetic oil they are putting in or is it just a mix...since i don't drive my car very much (21,000 in three years) and i follow the FSS counter i usually get my oil changed once a year...i thought maybe i should be using synthetic oil instead...maybe something like mobil 1....thanks in advance...

I think it would be wise to switch to synthetic. I don't know if the oil they put in was synthetic or not. Since on a 99 you would be responsible to pay for all the maintenance yourself, you can tell if it's synthetic by the price. The non-synthetic at most dealerships would run in the neighborhood of $2 a quart, the synthetic would probably be 6 bucks a quart, and the engine should have had 8 1/2 quarts put in. At our dealership, the oil is in bulk, both the synthetic and non-synthetic, so we can charge out a 1/2 quart, your dealership may have charged you 8, 8 1/2, or 9, depending on their own capabilities. So, if it's synthetic, you would have paid roughly $40 to $55 for the oil alone, or if it wasn't synthetic, it'd be more like $16 to $18. I'd recommend the Mobil1 0W-40 if you can find it. Also on the oil, if the price is confusingly in the middle of the range I speculated, just call the dealer and ask what type of oil the Castrol is that they put in.....Gilly

For a short while, MB dealers in the UK supplied cars with Castrol GTX Magnatec, a fully synthetic oil. I believe some still use this at service time in preference to Mobil 1, which has become the recommended brand.

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JJ Rodger
2013 G350 Bluetec
1999 SL 500
1993 E300 diesel T
1990 190

Since MB has signed a big $$$$$ with Mobil/Exxon, all of the US dealers have to suggest that oil as the BEST!

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Well, not to brown nose MB or Mobil, but I've never heard anyone say Mobil1 is BAD oil...Gilly