Heater Elbow Hose fitting question

I replaced my heater elbow (black plastic)fitting; the one positioned between the belt tensioner and the intake manifold this past June and it starting to leak again. The last time the elbow cracked, but this time it looks like the o ring is deteriorated. Was I supposed to use some lube or RTV on the fitting?
Thanks

The O-ring may have simply been bad when you installed it...but a little bit of lubrication when you replace it will help keep the O-ring from the friction of sliding in. I used a little dab of RTV silicone when I replaced the ring on my brother's 88 when it the old one started leaking and he hasn't had any problems with it since.

Thanks for the advice Alibi, I'll butter it up this time!