I'm not an engineer, but Vaseline is not designed to lubricate moving parts (at least not on reels). ABU and Penn both sell tubes of reel grease and I always use these. Vaseline should okay smeared thinly on the inner surfaces of the side plates as a water repellent though.
I don't own an Abu, but I am a racing cyclist and we use very a good waterproof grease for the bike bearings, I have used it on my reels and find it excellent. You can get it from any Good bike shop ( Not Halfords) that specializes in lightweight racing machines, far better than Vaseline.