I've recently bought a Kyosho PureTen EP Alpha 2 Subaru WRX from my nephew. I don't really know anything about them or radio controlled models generally, but I'm familiar with working on road cars.

My model came with the original nicad batteries, plus some new ni-mh batteries. My nephew said the nicads had been banned, but not sure if it's still ok to use old ones.

I tried it out last weekend and it goes really well. I had a slight issue with the steering which was fine turning in one direction but didn't move as far in the other. I had a look, and there seems to be some play in the servo saver, although it doesn't look like it's broken. I put a small cable tie around it, and the steering seems much better but I don't think this is a particularly good idea, having read what the servo saver is designed to do.

Can anyone give me any general advice on using the car, or advice about the steering issue?

well you can buy a new servo saver just make sure its splines match the servos.

As for batteries the Ni-Cd's are probably old as hell, and are generally crap even 16 years ago when I was really into RC's Ni-Cd's were rare due to how bad they were all around.

From what I see the RC came out late 90's early 2000's... so the electronics might not like LiPo's very much. NiMh's for RC's still seem to be sold. Basically mAh is run time, and cells are voltage. It all depends on your charger what you can get.
https://www.amainhobbies.com/ecopowe...-5023/p1532757 probably would work all though I think its a tad expensive might need a different connector as not sure if anything was done to the RC prior.

He actually gave me a charger for the new battery so that's good. I assumed the new battery would have a longer life being that much newer and current technology.

How long would you expect a battery to last. I think mines a 7300. When I ran it last week it seemed to be slowing down a bit after about 10 mins or so.

yea.. there are no 7300mah NiMh's unless it is mislabeled.
I think the highest I've seen was 5000
depending on how you were driving it, on what kind of surface, and electronics setup it could vary drastically. But I'm guessing it has 20+ year old electronics in it due to the model... I would guess is a 1500-2000mah battery for 10 mins of runtime... or it is severely degraded, or out of balance.
If its out of balance it will give the charger false positives saying its full when its no where near it. Only real way to fix that is run it, let it die, and recharge it, and repeat. Each time it should get slightly longer. From what I recall my NiMh it took like 15 runs to get it to full capacity as when I first got it the thing would say it was done charging at less then half the capacity. Charger I have has a readout saying how much power it put into the battery. Granted its been 16ish years since I used a NiMh in a RC as I switched to lipo eventually.