I just took a flashlight and looked in and around the engine everwhere that I could "visually inspect" and could not see ANY oil ANYWHERE from under the hood. I have not yet took off the undercarriage and looked from there though. Wouldn't I be able to see oil from under the hood though if the head gasket really in fact IS bad? I looked around what I think is the head gasket (the area between the block and the top of the engine) and couldn't see oil anywhere. Now I'm baffled. Should I let the dealer change it anyway if it isn't bad because it's under warranty and I might aswell get it done with the upgraded one (if it hasn't been changed already, don't have any maintenance records)? Help please!

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)