So what grade is everyone here using for engine oil? Our oil suppliers here(shell, mobile, caltex, castrol etc) are all recommending 20w-50 for a '75 260z

If Im in Sydney, average temp range 7*C (44F) - 40*C (104F) 5,000 Kms on a recently rebuilt stock engine (weekend street + a few 1000+Km trips now and then) could I go lighter or should I stay with the 20w-50?

I notice a lot of our overseas collegues use a lighter oil 10w-30 (for example), though their temperatures are probably cooler than ours

I think this may be of interest to you. http://www.micapeak.com/info/oiled.html I used to use 10W-40 exclusively. After reading this, however, when I get back in October, when I go back to 30 or 40 for the Skyline. I use a 10W-40 here in Japan and the temperature ranges 0 (32) to 40 (104) where I live.

Im using a 20w-50 i got from repco (generic brand oil) seems to be going ok