Applying polyurethane directly to the floor is considered a natural color. Given the age of the floor your going to get a honey color. If its red oak you'll get some pinks but def not as much as if it were brand new.

Water bourne urethane will give you the lightest possible natural color. This will really let the natural color of the wood show.

Either obe of these will not darken the grains. The darker the shade of stain the more the grains "pop".

Standard practice is to add 3 coats of polyurethane. With a light buffing inbetween coats. And generally a gallon will cover 500 sq ft. But thats going to vary. With the older wood its probably going to soak quite a bit in the first coat. By the last coat though you'll probably get about 750 sq ft a gallon.

Thanks for the info. We like the idea of getting a honey color. If we wanted to get some popping of the grain, would the Minwax natural stain do that without darkening the wood?

No the natural stain wont. If you did a side by side sample of poly and that stain it would take a pretty good eye to tell the color difference.

Are you looking to get some darker grains?
If so i have a couple of options you could think about.

Try the color "fruitwood". I believe its a minwax color. Its essentially natural but with enough pigment to darken the grains slightly.

The other would be if you wanted to mix up a custom stain if you cant find fruitwood. All you need to do is take you natural stain and add an ounce of ebony stain. Basucally its one ounce per gallon of stain. You could add more if you want more grain popping.

One problem you will have is that you have nowhere to test the stains.

If you want to accent the grain with minimal color changes, one of the best ways is to use a medium-color penetrating oil stain, apply lightly with a cloth dipped in well-stirred stain, and wipe it off very quickly and well, so the color stays in the pores of the grain and doesn't have time to soak into the rest.

Adding a tiny bit of ebony to the clear stain would make it possible to fille the pores with a dark color ... wipe it off quickly! Then do the clear topcoat.

Looking at my stain test boards from the bath, done on new oak:
Minwax Penetrating Oil Finish
Birch was light brownish
Light Cherry was quite red
Golden mahogany was neutral medium brown
Colonial Maple was reddish, but not as red as the cherry

All the info you've provided has given us an idea. We'd like to have the oak be a honey color but with some popping of the grain. What if we used the minwax golden oak stain and then a water-based polyurethane? The stain to get the color and popping, then the water-based poly for a quick, clear sealing.

Just out of curiosity, if the minwax natural stain doesn't pop the grain, why would anyone ever use it? Is it for furniture projects that won't be sealed with poly?

Thx to all.

Natural stain is used for many reasons. Mostly from my pov as a pro. I use it sometimes if im a time crunch. Ill stain natural and then in a few hours apply the first coat of poly and doing this not only saves me time from poly drying but i dont need to buff inbetween a natural stain and the first coat of poly. I can just apply it. Which knocks off about a days time. But i more or less use natural stain when i custom mix stains.

I run into situations all the time where a customer loves a stock color but would love it just a shade lighter.

You can use water bourne urethane over stain. Just be sure to give you stain ample time to dry. If you try to apply the urethsne too soon. You risk pulling color and causing streaks in the finish.