-- Last Updated: Nov-07-12 12:57 PM EST --
Deks D1 is a penetrating oil that results in a finish similar (but better) than Watco oil. Both are very different from the finish obtained with a good quality varnish, however. The difference in the finish is very readily apparent. Although Deks is more durable than Watco, it doesn't have the staying power of polyurethane or spar varnish, but it doesn't scratch up the same either.
Watco makes a Satin Wax product that can be applied over their regular penetrating oil that does produce a fair satin finish but not as nice as using the Deks D1:D2 mixture. To my knowledge, Watco doesn't make a product that produces a finish equivalent to the high gloss finish obtained by applying undiluted D2 over D1. I haven't tried applying varnish over Watco. I don't know how that would work out.
When I bought my first wood gunwaled (an MRC Explorer) back in the 1970s, I bought a quart of D1 and D2 from a local supplier in Minneapolis and used it every couple of years until I moved. After that, I couldn't find Deks locally and switched to Watco oil and have used several varieties. It is pretty easy to apply a quick coat of Watco, but I find that it doesn't stay nearly as well. After car-topping my boats and paddling them there are often bare looking areas along the midships gunwales and where the racks contact the rails after even one weekend trip. And I have never gotten as nice an appearance with Watco as with Deks, although Watco is not bad.
I think if you would use the product the difference in qualities between Deks and Watco would be immediately apparent.
White ash varies somewhat in density but is generally considered a denser wood, not as dense as some teaks, but comparable to maple and most mahoganies with some varieties approaching the density of hickory. It is generally considerably denser than spruce and most pines.