Even though you can’t really do a proper oil change without first starting the engine and warming it up , it would probably be better to drain the old oil from the sump , add fresh oil to the correct level , and before attempting to start , remove the spark plugs , put a SMALL amount of oil into each cylinder , and crank the engine round by hand .
Then , with spark plugs still out , crank it over on the starter a few times , before putting the plugs back in .
This would give it some lubrication before starting after such a long time .
Also worth changing the coolant , with a flushing agent before putting fresh stuff in .
Check all rubber drive belts , radiator hoses and other parts which may be perished .
For safety , I’d consider the tyres to be shot ; I just recommissioned a W140 with a set of tyres which had been stored about 10 years , and they deteriorated within a very short time , so were replaced .
Don’t , whatever you do , try to jump start a R129 - you’ll fry some of the modules , especially the very expensive roof controller . On that subject , syringe all the old hydraulic fluid out of the reservoir under the spare wheel , and refill with fresh ZHM fluid .
Expect the soft top may need multiple attempts and much perseverance to get working again after a long layup . Keep trying it , maybe work back and forward by hand - it will come back - you will also need to reset the door windows after a battery change , otherwise the roof won’t work .
They are lovely cars and well worth the effort .
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