It is better to match at least two tires. This helps keep the car running in alignment and will give you better control. If you have a good, full sized spare tire, one idea would be to match it and put the two on the car, using the worst or mis-matched tire as the spare.
Replace it
You dismantle it and replace the seal.
How to replace a heater hose on a 2001 Oldsmobile silloute
you replace it
replace the seals
Replace the plug.
There is a crack in the battery case. Replace the battery.
Take it apart and replace the main seal.
Replace it, or pour in a tablespoon of powdered metal, available at any autozone/walmart. That should help on small pinhole leaks, but for large ones, you'll need to replace the whole thing, or have the leaks welded. Unless you bought the plastic one I got, in which case you'll have to replace it, and forget the powdered metal. Oh and pouring Mountain Dew/Pepsi in there will not work.
Replace it with a new one.
You just need to replace the washers. anonymous@oola.com
You can replace the rubber gasket.