DON'T BUY A BOUCH ELECTRIC JACKHAMMER.
The seals are designed to fail after 100 hours of use. Bosch rec emends to take the jackhammer to them after 100 hours of use so they could soak you for a huge repair bill. Bosch jackhammers don't have a window on them to tell you when to add lube so its easy to overlook low oil. Try your luck on the Internet and see if you could find out how much lube and what type to add. No one has an answer. The dealer has an answer. Take it to them.
Don't buy any electric jackhammer that doesn't have a way to check the lube level without disassembling the unit.
Greg
March 2011