Typically I do not, even though I am in my 40s. Occasionally I shave a few years off just for the fun of it. [which means I am still 2x their age]
Not one girl has ever cared. I actually had this college girl ask me how old I was mid-fuck which was hilarious.
'Are you 36? No.
37? No.
38? No.' She stopped asking but never stopped grinding on top of me. We banged dozens of times after that.
any girl who's 20 thinks everyone over...say, 27-29 is 'old' for her, which doesn't mean she doesn't want to fuck them. If they're running away from you, 95% of the time your age has zero to do with it. You can be 30 or 35 or 45.
Kristian, I suggest that you showing discomfort about the age difference is leading them to be uncomfortable with it. If you seem fun and experienced and non-judgemental, they'll want to bang you regardless of age. Most girls that age are actually looking for an older guy or they wouldn't be talking to you in the first place. It's amazing how fast college girls get tired of keg parties, bad sex, and pizza for dinner these days.....they want a totally different experience.
Give it to them.