# Oil for Z?



## ekmixon (Aug 12, 2005)

I recently bought a 1991 300zx coupe. It has 90k miles on it. I know the previous owner had synthetic 10w-30. I don't know what brand. I wanted to know what has been the best synthetic oil to use and what weight? Thanks.


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## JAMESZ (Mar 12, 2004)

Factory is 10w-30 keep it. I like my mobile 1 synthetic.


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## NisMOFO (Jun 2, 2005)

one of the best would be royal purple


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## Bror Jace (Apr 26, 2003)

Royal Purple thins out too quickly. I'd rather have a good conventional oil in my ride than that stuff.

*elmixon*, do a search of this forum using "oil" or "synthetic" and a few of the more prominant brand names like "Mobil," "Pennzoil" and "Chevron" to see lots of past discussion.


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## Spongerider (Nov 18, 2002)

Amsoil 20W-50.


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## Zen31ZR (Mar 24, 2004)

Spongerider said:


> Amsoil 20W-50.


Isn't that a bit thick?


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## Spongerider (Nov 18, 2002)

Zen31ZR said:


> Isn't that a bit thick?


Nope, I rather lose a few hps. to gain engine longivity.


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## Zen31ZR (Mar 24, 2004)

Spongerider said:


> Nope, I rather lose a few hps. to gain engine longivity.


I ran 15w40 in my Z and felt it was sufficient, is all I'm saying. 10w30 in the winter and 15w40 in the summer. I don't feel 10w30 is sufficient as a summer oil by any means, certainly not in a turbo car.
I have heard about blown seal problems with cars using the higher weight oils, particularly the front seal. The one I heard the most about was the TT Supra.


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## Spongerider (Nov 18, 2002)

Zen31ZR said:


> I ran 15w40 in my Z and felt it was sufficient, is all I'm saying. 10w30 in the winter and 15w40 in the summer. I don't feel 10w30 is sufficient as a summer oil by any means, certainly not in a turbo car.
> I have heard about blown seal problems with cars using the higher weight oils, particularly the front seal. The one I heard the most about was the TT Supra.


I have never heard of the Z32 having problem with 20w-50 oil. I only started to use such a weight at 100K.


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## Bror Jace (Apr 26, 2003)

Guys, the only way to know how an oil is _really_ doing is to run a UOA ... Used Oil Analysis.

http://www.blackstone-labs.com/free_test_kit.html

or 

Butler Labs: 701-223-0890 ask for Scott or Ed

Cost is $20-$30 depending, depending.

I've seen where thicker oils seem to be providing less wear ... and others where the heavy film produced strain on the engine and wear seemed elevated. 

I too like 15W-40 oils in high-performance applications. Very robust, shear-stable oils which also have enhanced additive packages to deal with high engine pressures (especially high valvetrain tensions) and greater detergents/dispersants.

My fave is Schaeffer 15W-40 ... but the best mass-market 15W-40 is Chevron Delo400. Look for the label which proclaims "New low-wear formula" as this formulation has a great deal of molybdenum in the formula ... a potent anti-wear additive.


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## ekmixon (Aug 12, 2005)

JAMESZ said:


> Factory is 10w-30 keep it. I like my mobile 1 synthetic.


I live in fl so the weather is hot most of the time. Is 10w-30 still a good weight to use? I have never used synthetic before. How often do you change synthetic? Thanks


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## Bror Jace (Apr 26, 2003)

Thanks to the EPA pushing the oil industry, most 10W30s will shear out of grade in about 2,000-3,000 miles, even some synthetics.

XW-30 synthetics such as Mobil 1, Red Line, Amsoil, Schaeffer hold their grade well ... although Mobil 1 starts out a bit thin.

Avoid mass market synthetics other than those mentioned above as most are group III mineral oil masquerading as "synthetic." 

5,000 miles is easy for the better, stable synthetics ... even 7,500 miles can be OK but I'd do a UOA to be sure the oil is holding up OK.

Of course, change the filter along with the oil.


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## asleepz (Feb 24, 2004)

What exactly would you suggest for a Z31 Turbo running 10 PSI? 

I need something for Summer and Winter here. I run anywhere from 70-105 in the summer and 30-50 in the winter.. I need some weight help here. 

My dad keeps telling me 5W-30, but he doesn't believe turbo cars take something different than your average weight.


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## Zac (Mar 10, 2004)

Amsoil is an exceptional oil but it has shown a tendency to thicken. Redline has not shown to be a good oil for long drain intervals but it does clean. I run Water Wetter by Redline and that is a hella additive. I ran Amsoil for about the first 35k miles and was happy with it. I now run Chevron Supreme because UOAs show this oil to be as good as most synthetics and it is like 2 bucks a quart. No complaints for either one. If you are looking for a good oil to run for lower drain intervals, run Chevron Supreme.


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## asleepz (Feb 24, 2004)

What kind of weight would you suggest.

I change the oil every 1500-2000 miles.. So really longevity isn't a stong point for me.


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## Bror Jace (Apr 26, 2003)

*asleepz*: _"What kind of weight would you suggest? I change the oil every 1,500-2,000 miles ... so really, longevity isn't a stong point for me."_

Honestly? Any oil will work well for such a short interval. The add packs in modern thin oils seem to protect well ... even when a XW-30 oil shears down to a 20 weight at temp. There's a guy on BITOG running a 0W-20 (Mobil 1, I think) in his late-model Ferrari just to show that thin oils can protect well. Talk about putting your money where your mouth is! 

For people stressing an oil, a lot of it has to do with oil temp ... especially oil temps that spike because the oil comes into contact with the piston ... or a turbo's bearings. No sense in running a heavyweight oil if the temps are never getting above 240 degrees. It will just rob you of fuel economy and power ... and ridiculous heavweight oils can even increase wear in some applications.

I've seen Subaru WRX UOAs and you'd swear that turbo engine was one of the kindest to oil. Part of the reason? A very well-balanced (boxer) 4-cyl and liquid-cooled turbo housing.

So, if you can install a good oil temp gauge and monitor your oil temperature, that would be a wise investment. 

Personally, I think any 10W-30 would be fine for up to 2,000 miles in your blown beast. My preferences go with Chevron Supreme, Havoline and Pennzoil. All three use Group II+ base oils with stout moly/boron additive packages.

Want to do a little blending and stabilize the oil some while boosting additive levels? Use Chevron Supreme in 10W-30 and add up to 20% of Chevron Delo400 in 15W-40 to it. Be sure it's the newest formula with the yellow flag on the front which says "New Low-Wear Formula." I saw a UOA of one guy running this blend and it's the type of result which makes synthetics seem silly and pointless. 

I found a local Chevron distributor in my area and want to try Chevron Delo400 in 0W-30 this winter.


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## Zen31ZR (Mar 24, 2004)

Bror Jace said:


> I've seen Subaru WRX UOAs and you'd swear that turbo engine was one of the kindest to oil. Part of the reason? A very well-balanced (boxer) 4-cyl and liquid-cooled turbo housing.


Should be similar for a 4G63T and later model VG30ETs as well. The 4G63 is a pretty well balanced 4 cylinder and has a liquid cooled turbo. The VG30 is pretty well balanced for a V6 and has a liquid cooled turbo. I've had both, but never ran UOAs on them, unfortunately.


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