To have to add a little makeup fluid after 120kmiles and 15 years doesn’t qualify as a leak IMO. Some of that is evaporation, and there’s no such thing as absolute zero fluid loss. A minuscule loss rate would add up to hitting the add mark after 15 years. I’d assume no leak unless it drops in a short period of time after topping off.
HOWEVER - You might look for wet areas - particularly on the driver’s side of the radiator where the cooler lines from the transmission go into the radiator - they often develop leaks where the rubber hoses get clamped to barbed fittings (at the radiator). Tightening those clamps almost always takes care of it. If not, one of the hoses may have a hole in it under the clamp. The clamps can be difficult to reach to tighten. The clamp screw heads take a 1/4” open end or socket (has to be a 6-point because the clamp screw head has round corners on the hex shape - but also there may not be enough space between the clamp screw head and the clamp band to allow the socket wall thickness, in which case use open-end wrench.
You can get filter and gasket set at auto parts store. Chrysler originally had no gasket - they specified a special transmission-grade Mopar RTV, and later came out with a metal re-usable replacement gasket - the Chrysler part number was posted several times over the years, but search doesn’t work very well for older posts. But people have been using the aftermarket filter/gasket sets without problems - IMO, the most practical solution.
I suspect any Valvoline ATF+4 is the same thing - maybe they changed the labeling. Do they actually have two part numbers listed for Valvoline ATF+4 and the prices are different? Or are you seeing different labeling on older and newer lots of the same fluid?
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs
Last edited by peva; 11-24-2019 at 12:18 AM.