After sitting for that long the cylinders have probably lost all their oil too as it would have run down by now.
Oil in the rings helps compression so I personally would shoot a couple of squirts of oil into each one and let it sit overnight.
I used a squirt can and a piece of fuel line to get through the GP holes.

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique