Not a problem to store a gas cart in a garage for weeks.....or months (provided there are no leaks in the tank or fuel lines).
Different schools of thought on the empty tank vs. full tank mindset. I always store ours with a fairly full tank. Less potential for condensation forming in the fuel tank during storage. For an example of this, look at a partially filled soft drink container or water bottle that sits for a while. Condensation forms on the empty inside surface of the bottle, particularly when there are swings in the temp and/or humidity levels. I'd prefer to not have that happening in the fuel tank.
Also, I don't jam it 100% full to the brim to allow for some room for expansion of the fuel if needed due to temperature rise (comes out of the underground tanks at the gas stations at a cooler temp than might be experienced once the fuel is in the tank).
JMHO!! Hope it's of some help to you.
Bill
