I changed after the 1200 break in to Castrol GTX, and then again at 3750 to Mobil1 Syn and filter. At the next change I am going to switch to either Mobil1 0w-40, or preferably Castrol 0w-30 if I can find it. I am wanting to go 7k interval, but I drive mainly in short trip/ stoplight city/ traffic land; am I safe to go 7k b/w changes, or should I stick w/ the recommended 3750??

 

I have run syn since day 1 in my work truck!240,000 still running strong!

 

my first oil change was to mobil1 full syn. car is running amazing and i change it every 2000 - 2500 miles. once the car is broken in - it seriously can't hurt to keep the oil fresh.

 

not sure why all you guys in warm climates are running 0w30 or 0w40, you would be better off running a 10w30 or 10w40 since with warm weather and 0w youre not doing your engine any favors on initial start, that oil is real thin before the engine warms up. if you arent seeing negative temps in the oil change, you should be using a 10 or 20 winterized.

edit: check out this chart, makes it easy

http://www.aa1car.com/library/oil_chart.jpg

 

Thats a good question for the oil threads lots of knowledgeable people in there. But you probably will never get a 100% bona-fide answer because most of the stuff is speculation at best.

 

That's a pretty incorrect assessment.

Will

 

i have to do it every 500miles right now.

 

What do you consider a 100% bona-fide answer? He's wrong on all accounts, but what would be good proof? Want the math on oil viscosity at various temperatures to prove it? That would be easy to post, but how many people understand J300 specs and the difference between centipoise and centistokes? I could describe what the difference is and give some examples, but then you're taking my word on it and is that considered bona-fide?

Will

 

If you really want to learn about oil, and specifically about oil in relation to your Z, listen to Will (Resolute) and read his UOA threads. Will's post are filled with great information and data -- not speculation. A bunch of people on these forums (including quite a few in this thread) talk about oil like they know what they are talking about, when they obviously don't know jack.

 

care to elaborate?

 

Not in any way calling you out like you're wrong, i'm just eager to hear your full input on this...please?

 

Sure.

Viscosity is a function of temperature. To put it simply, the colder it is, the thicker the oil is. The hotter it is, the thinner the oil is.

It is incorrect to say that the oil is "real thin" before the engine warms up, because the oil is thicker when the engine is first started than when the engine gets to operating temperature and heats the oil.

This is why we have multi-grade oils. The multi-grade oil allows us to have a 30 weight oil when the engine is hot, but only a 5 or 0 weight oil when cold. This keeps the oil's viscosity similar across a broad operating range, compared to a straight 30 weight whcih will be a very thick oil when cold.

Now, even with multigrade oils, the oil is still thicker when cold than compared to when hot. It's just not as extreme a difference in viscosity as a straight 30 weight oil would be. So, even though a multi-grade oil still thickens up with cold, and thins out with heat, the viscosity change isn't as extreme as with a straight weight.

The oil's effectiveness in maintaining a viscosity spread that is fairly even across a broad operating range of temperatures is measured as it's viscosity index. The higher the VI, the closer the oil's cold viscosity is to the hot viscosity.

Thicker oil is harder to pump, and takes longer to circulate through the system. Therefore, having an oil that can stay as close to the operating viscosity as possible, while it is still cold, is a good thing. This means the oil thins out less with heat, and circulates faster upon start-up (the most critical time for wear).

So, a 0W-30 is still a 30 weight oil when hot, but when cold it is a 0 weight oil. A 0 weight oil when cold is still thicker than a 30 weight oil when hot, but the viscosities are a lot closer than a 5W-30 or straight 30 weight would be. The 0W-30 will circulate faster on start-up, protect better on start-up, and have lower pumping losses while cold. When it heats up and thins out it will still be a 30 weight just liike the others.

Whether or not anyone NEEDs a 0W-xx oil is hard to say, since the oil temp when starting the engine varies. There is absolutely no downside to using a 0W-xx oil, however, since it will pump easier than a 5W-xx or 10W-xx oil. Plus, to achieve a 0W-xx grade, better chemistry is usually involved than their older 5W and 10W spec'd counterparts.

There is a more detailed write-up on oil viscosity in the UOA/Oil Data sticky. It has some numbers to crunch for those who wish to read-up a little more on an often hard to understand topic.

Will

 

dealer = salesman that read the f'n brochure. um i did one at 500 one at 1,000 and then every 3,000 thereafter. at 10,000 switching to synthetic (royal purple)

 

awesome, thanks for the clearing up.

 

i guess i should have stated that differently: im disappointed that you all are ok with the extra wear you are getting by using that 0w oil. the point is that just because it flows better doesnt mean it is the right stuff to use. the 0w is too thin at warmer temps and you arent being protected adequately. as it is, nissan recommends a thinner oil here in the states so that they can get the benefits of using energy conserving oil. in europe, they recommend 10w-30 in most of the cars unless it is in a cold area. going thinner than the already thin suggestion...i guess thats your choice

 

A.) you should at least understand multi-grade oils.
B.) Will explained in a very simple summary how multi-grade oils work.
C.) once then engine has warmed the oil, it's not a 0 weight oil.

 

Your summary is inaccurate in every respect.

Will

 

My summary is accurate in every aspect

Trevor

 

a) i do
b) i know
c) were not talking about a warm engine

 

yes, we are talking about a warm engine.