some thing an old timer told me, if you use dino oil,when your car burns oil you get blue smoke.
try some mobil 1 syntec oil, syntec does not have any color, and it may also get your valve guide seal's sealing again.
i have seen this work very well.
good luck
rich

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88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car