So I'm doing my first oil change tomorrow on my 87 TII. I was recomanded getting castro gtx 20w50. I was wonderig is that good? And also what oil filter should I get? And is there any things I should look out for while doing this? Thanks in advance!

 

GTX 20-50 is ok but if you are worried that it may be too thick you can use 10-40. Really, its user preference for the most part. Everything else is pretty normal for an oil change.

 

20-50 is fine where you live. just remember to double check your work

 

And oil filter?

 

try and get an OEM(mazda) filter.(madzatrix,atkins,..spooledupracing has them)
some of the aftermarket stuff such as Fram are crappy paper filters that can(some do) break under pressure and can clog the oil system.

 

so in regards of oil filters. where can I get them? websites anyone? thanks.

 

You can get oil filters at any auto parts store.

The Mazda filters are available at the dealer.

 

I normaly use 10W40 and every 3000 a new oil filter.

 

So after draining, how much should I put back in?

 

Start with 4 qts. Check the dipstick. Add as necessary. Oil level should be in the hashmarks on the dipstick.

 

Thanks!

 

And for the record, you will find oil change information in the Factory Service Manual which can be freely downloaded from the FAQ.