Even without a dipstick I still bet you the stealer uses a topsider. It would be mighty old fasion to have to use a drain plug. You would just need a different adapter for the top sider to make a seal.

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My Daily : 96 E-300 Diesel with 195,000 miles
Retired: 92 300D 2.5 T 345K miles and for sale
Retired: 95 E320 157K miles and currently parked with blown engine

Both retired cars are for sale as is my w124 shop inventory