When going down a 3 or 4 mile downgrade on a 4 lane highway I dont’ have my foot on the gas but my speed increases. I’d say about 2 mph every quarter mile. Other drivers in fromt of me are not touching their brakes (no brake lights) but I have to hit the brakes every so often to keep within the speed of the rest of the traffic. I don’t have a tachometer so I don’t know what the rpm’s are during this. It idles fine at stop lights. Runs fine otherwise.
Try turning off overdrive or downshifting one gear with the gear shift. This should allow the engine to help brake your descent. This will also save your brakes for when you really need it.
And maybe even save a little bit if fuel.
Your car is normal and just fine. Some cars have transmissions that just “roll” and don’t generate much engine braking. European cars with auto transmissions tend to be set up to provide more engine braking than domestic cars when in “drive”.
If you want engine braking on downhills you can check your owner’s manual look for “mountain driving”. If your car has an overdrive on and off button then turn the OD “off”. If it has D1 or D2 (or D4 and D5) shift to the other D and see what happens. Tapping the brakes isn’t really a problem either and you can just drive on as it is.