Best lube for 3" waste fitting

[RV_daytrader]

My dump valves are getting hard to operate (29 years old!) and so I'm replacing them and changing the piping so they will be higher off the ground.
Anyway, the tank looks to be fiberglass? (see pic) and the abs fitting that goes in it has an o-ring and a clamp to hold it together. I am wondering what to coat the fitting with to make it slide in easier and help it to seal also.

[RV_daytrader]

Thanks guys....looks like I'll use plumbers silicon grease....one regular plumbers grease Home Depot sells says NOT for o-rings.

[ScottG]

donn0128 wrote:
Plumbers grease. Available at any place that sells plumbing supplies.

X2!

[donn0128]

Plumbers grease. Available at any place that sells plumbing supplies.

[phil-t]

Go to the auto parts place and pick up a tube of silcone grease.