Why is maple syrup less viscous than other liquid sugars? I really enjoy making this recipe for oatmeal-raisin cookies:
http://viveleveganrecipes.blogspot.co.uk/2007/10/oatmeal-raisin-cookies.html

However, I'm based in the UK, where maple syrup is much more expensive than in the US or Canada. If I make this recipe, I usually substitute golden syrup or honey. However, I've noticed that both of these are much more viscous than maple syrup, which means that when I get to this step:


  combine syrup, molasses, and vanilla, then stir in oil to incorporate


I find that the syrup doesn't mix nicely with the oil to give a smooth mixture -- you get more of an emulsion instead, which affects it's ability to lubricate the dry ingredients. The recipe still works if you add a bit more liquid (either more oil / melted butter or a bit of milk), but it leaves me with a couple of questions:


Why is maple syrup less viscous than other liquid sugars? Is it a different ratio of glucose, fructose and other sugars? Or just a higher water content?
Is it possible to thin honey or maple syrup to get it to mix more easily with the oil? 
Is there another sugar syrup that would have the same viscosity as maple syrup that would work better? Taste isn't really an issue here -- the spices in the recipe drown the subtle flavour of maple syrup, so any neutral tasting liquid sugar should be fine
Maple syrup is more liquid because it contains more water.

That also depends on the type (category) of syrup; most consumer syrup will be on the lighter side of it and will contain more water as the darker ones because it will be less concentrated.

You could dillute honey or Golden syrup with water to have a lighter syrup but the cookies will taste different.

Maple syrup grading in Québec
http://fpaq.ca/en/federation/quality/grading-system/