Hi everyone. ('84 1.9L gas)

I just bought this van, and I don't know what oil the PO had in it.  The
filter was junk though. I'm now running it with castol gtx 5w-30 (as best I
can remember) with a mahle filter. I put in this oil as a cheap stop-gap
before going to amsoil.  I was ignorant to what grade oil to put in, and put
in what I had around... a poor choice. I replaced three pushrod tubes (with
collapsables) when I changed the oil.

Before I changed the oil, the oil pressure light never came on,  now it
comes on after the vehicle it at operating temperature. I guess, no suprise
because I think I have a light weight oil in it..

My local parts supplier (who sells amsoil) recommends that I use 15w-40 year
round.

1. Do you think the oil light is likely to still come on?
2. Is 15W-40 amsoil what you would recommend? I've heard wonderful things
about this product (amsoil)
3. From somewhere on the web, I read that you should clean the oil pressure
relief valve.  I intend to do this.  Would you?

Thanks

Brad