The best way to clean a large floor, or even a small one, is a floor scrubber. It successfully removes dirt and grime and sucks up all the dirty water in one pass. But this brings up the question of what type of cleaning solution should be used so that the machine works to its fullest potential.
When using a floor scrubber you will need to use detergent to clean up the oil, dirt and whatever else is making your floor dirty. Which one is best? Every application is different and may require different products. In every situation, make sure to follow the guidelines on the product you are using. Mixing a concentration of any kind of cleaner too strong is expensive and can cause damage to the machine. Make sure it is a low-foam detergent. Foam in the recovery tank will get into the vac motor and damage it. If this is happening you may need to use de-foamer in the recovery tank.
While some amount of cleaner is good to remove dirt, in most instances, when just cleaning a dusty warehouse floor,less detergent is usually okay. The machine is going to do most of the work anyway. When you do find a dirty area like a loading dock or greasy area, try double scrubbing. Double scrubbing is scrubbing the floor with vacuum off and squeegee up while putting plenty of solution on the floor. Give the solution some dwell time on the floor so that the solution has time to work. Then go back with the scrubber, this time picking the water up off the floor, and see if it is clean. If you haven't had a floor scrubber before, you may have to double scrub a lot of the floor the first time you use the scrubber to get it clean.