Oil Question
 

What would be a good viscosity of oil for 90 -100+ temperatures in Texas? I currently have the standard 5w30 in it right now but a change is coming up and I figured I would try something different since we have been experiencing 100+ temps for weeks on end now. I was thinking about trying out a 10w30.

I think staying with the 5w-30 would be fine. Maybe just go with a good brand like RedLine or something.

Running Castrol in it right now and it runs good but I definitely was thinking about switching to Redline or Mobile1 to give it a try. Just wanted to see if anyone was running 10w30 and if it was worth trying in higher temperature areas.

0w40 mobil1 is the only true synthetic made by them and i use it with my Twin Greddys

In theory, there is no diff between 5W30 and 10W30 at operating temps.

/\ x2, that's what we run as well.

No reason to switch.

I like the GC (Castrol 0W30). True synthetic, amazing oil.

5w50 would be a change in the oil when it is operating at higher temperatures. You should be fine with 5w30, you just need a ester based oil. Ester works better in higher temps so it doesnt heat up as easily. Redline is what I'm currently using because it is a fully-synthetic ester based oil. I noticed about 10~20 temp drop when I switched over.

I use Mobil 1 racing 15w50.

You want a high viscocity for higher temps here in Texas as that is what protects the motor at higher operating temps, which the 370z definitely sees.
The W number has only to do with cold starts which are all tested below 0...

Oil's with viscocity of 0w40, etc are good for cold weather and cold starts, but act like a 40 weight at operating temps. the 0w stands for 0 weight in Winter conditions.



What makes ester oils good though is not their resistance to building heat, but their resistance to shearing, extended interval length, etc. They basically keep their viscosity rating through a broader range of their service interval length.

So when lesser oils are near the end of their service life, the viscosity of the oil is generally reduced compared to the advertised rating. This varies between oil types and brands. It can be quite disturbing with some oils to see just how far from advertised they become after a few thousand miles

So, really you should look at a high viscosity oil than 30 for this motor if you plan to mod it or drive it hard, etc.
Or not, up to you.

I do some spirited driving with these 100+ temps but dont plan on tracking it yet. Oil temp stays around 220-230 on the street but was curious if I could potentially lower the temp 5-10 degrees based on the oil. I think I will run 5w30 redline and see how it does in these crazy texas temperatures. Thanks for the responses.

Just buy an oil cooler for around 190 shipped.
I live in Houston and with the oil cooler I run right at 185 in the mornings (around 80 degrees?) and around 200 during the afternoon. If I drive spirited during a really hot afternoon it goes to about 220. Made a huge difference.

The higher viscosity will be a lot better than a 30 weight oil though. The lower the number the less protection the oil provides at elevated temps.

The standard 0w30 and 5w30 oils are going to be in their sweet spot viscosity wise from 200-230 degrees. If you are regularly above that (i.e. dedicated track car or FI) then you might want to step it up to a 40 or 50. I can't see changing to a heavier weight oil on a street car as you are going to reduce performance of the oil in the 180-210 range, just makes more sense to install an oil cooler (the Mobil 1 0W40 is a possible exception). A 15W oil is not going to protect as well as a 0W or a 5W even on a 90F cold start. The winter weight isn't just for winter conditions, take a look at some viscosity charts. The quicker the oil gets to the ideal 10-12 cSt range as Nissan intended the better lubricated you are going to be.

Here's a good warm up chart. Note how thick the 15W40 is even at 35C (95F).
http://www.kewengineering.co.uk/Auto...comparison.jpg

^ makes sense to me

I disagree that ester oil, or at least Nissan's formulation is more shear proof than other synthetics. Here is my uoa on Nissan Ester. Notice it sheared out of grade at 3k miles. I switched to Castrol Edge Titanium, we'll see how that looks.
http://i139.photobucket.com/albums/q...ro/6_23_11.png

Thing is the grade range is actually pretty wide. So there can be as much difference in viscosity between a given 20 and 30 weight as there is between two 30 weights, with one at the light end of 30 and the other at the heavy end. You can see from the manufacturer's info what the oil viscosity really is at the standard test temperature. A person could use one that is on the heavier end while still staying with the manufacturer's recommendation. I wouldn't stray too far from that, a light 10W30 maybe, but 15W50 and such? No way. You could probably also mix grades of an oil to come up with one that is heavier, yet still in spec. This is what I may end up doing if the Castrol shears out of grade. I've read that M1 High Mileage is at the heavy end.

BTW if your temps are normal I wouldn't go out of my way to go up multiple grades just because it is hot out. 220F is not hot for these oils, they do the viscosity test 210-212F in the first place.

I am using Castrol 10w40 semi-synthetic since 2008 with no problem (its recomanded in our hot climate area) , i think the vq engines should only get semi-synthetic oil unless if your car FI.
Correct me if i am wrong.