I’m a huge fan of using lube for just about any sex act, but you don’t usually need any when you’re giving a blowjob. This is one activity where saliva is usually more than enough.
But I know from personal experience that just because it’s your mouth it doesn’t necessarily mean it’s wet enough. Sometimes, you have to make a conscious effort to drool a bit more, or think about dill pickles or sliced lemons to help you salivate