Yes the engine will be at the same temperature when warm, but that does not include when it starts and is driven until warm. That's only a real problem when it's crazy cold or crazy hot
10-W30 is just fine for almost all of the temperatures

As with Rod's Z, mine has always had 10-W30 in it and has never had the head off or any problems other then a fuel pump going on it.. it's at 191K miles and counting, driven everyday - hot or cold

 

everybody is comfortable using what they like to use=fact of life #1--nobody i know is saying ya has ta do dis.......no one hAS TO DO ANYTHING THEY DO NOT WANNA DO....oops... ...everyones histories are different asnd find different things to keep in their weird things to know file-----we each have different things we know to make things last longer.....and each one of our histories belongs in different climates, so what one person likes is different than someone elses needs.......an di gort no bubble, bro--i watch and listen and get around this world a lot--i know the names of those who speak to each other---we all have different bases for owr individual knowledge.....haveas much fun with your Zs a s i have with mine and we will all meet somewhere to discuss things------over beer!!!!! or soda or milk or something friendly---- and my main bearing went out because the oil pump failed at 244k miles.otherwise the engine is strong like oxen.....and running well, now....big difference between an old used engine and a newly rebuilt and blueprinted special engine........

 

You can run the thinnest oil possible that wont burn out of the motor before the next oil change. Actually, on healthy motors I have noticed that most will use less oil between changes if its not too thick. I run 10-30 in my z that has unknown actual miles on it and was driven hard by many teenegers, including myself. Burns a quart in 3k haulin *** miles, doesnt worry me at all. The other thing is that thicker oils wont flow as freely through smaller passages as the thin stuff will. you can do more harm than good to the top end with insufficient oil volume.

 

Exactly

 

Point taken, I'd love to have some grape juice right now haha.

 

I'm kinda late to the party on this one, but if you're just starting your motor after sitting for a while, use an oil with a high zinc content. i.e. valvoline vr1, or something similar. The zinc will protect metal to metal contact in flat tappet cam engines like ours. There was a huge stink about it on hybridz and most agree that you should use a higher zinc content oil, at least in the .12% range or higher. (VR1 is .21% or thereabouts) As for weight, I guess it all depends on where and what use you have for your Z. If you're going to see sustained high oil temps, use a heavier weight oil. For track use, I use 20-50, but on the streets it's 10-30 or 10-40 depending on where my oil temps end up.

 

5 W 30 for northern climates (if you plan to drive at all in colder temps)