ngent45 wrote: But in general, how many km can a gen 4 2.5i get before it starts to deteriorate?
I went 90,000km before the head gasket blew and took out the heads and radiator.
Also the sub blew around that time.
After an engine swap to one with around 40,000km, no issues until the car had done 150,000km.
That was mostly done running E85 with a tune, injectors and a 340lph fuel pump.
I traded it for my gen V GT. Which I got at 200,000 highway km.
On the gen V, Boot gas struts are gone. Heads lifting under boost. Knocking sound from left front of the car that I haven't diagnosed but isn't good.
After working in a subaru dealership I'd expect to rebuild the top end of the engine every 6 years or 110,000km on a gen 4 2.5i.
Because of head gaskets letting go.
My advice is if that happens, get the heads machined and use arp headstuds with a quality headgasket.
Oil changes every 6000km and frequent coolant changes so that the headgasket lasts.
Other than that they seem very good.
Never had any electrical problems.
Pro tip, don't spend money on it. Just stay on top of maintenance.