oil viscosity

[gilyZ06]

I have a friend that just bought a new 2004 commemorative Z06. He told me he didn't like the lifter noise on start up after the car had ben sitting for a few days. I told him that mine did the same thing and that I wouldn't worry about it. We thought that the oil viscosity 5w 30w is the reason and wondered why GM would recomend the same viscosity in all their vettes no matter where one lived, S.F. bay area for us. I told my friend that I would get some feed back from you all here at Z06vette. Also, are any of you using a different brand of synthetic oil? What viscosity, and why? Thanks, Gily.

[No Doubt]

They recommend a 5W-30 because they have no idea where a car will end up. That is, what type of climate. They also have to meet CAFE standards for mileage and other environmental rules. Therefore for street use they recommend an oil viscosity range that will work in all climates for normal street use. However, I wouldn't run a 5W-30 if racing in Arizona during the summer. (or just about anywhere else for that matter)

[gilyZ06]

No Doubt, What viscosity are you useing, and is it still mobile 1? Just want the best protection for my engine. I have nothing against mobile 1.

[No Doubt]

I run M1 15W-50 but it's a 427 and 5W-40 in the cooler months on the street. 0W-40 is also good if ambient temps at engine start are real low. But, I also have an Accusump so I can prelube the engine.

It depends on how you drive and what the ambient temperature is. OEM's recommend a weight that works everywhere for everyone, most of the time.

[No Doubt]

Mobile 1's 30 weight oils are on the low end as far as cSt. That is their ?W-30 weight is barely a 30 weight whereas Redline is closer to a 40 weight (even though it's a 30)

Not all oil viscosities are the same even though the numbers indicate they are.

[jdk]

I would think 10-30 would be better suited for cali. I also think that oil viscosity is going to have little to no effect on the noise the lifters make. If he dosent like noisy v8's tell him to get a japanese 4 cylinder

[No Doubt]

10W-30 would work fine in California as would a 10W-40 Synthetic. I hate to suggest the latter because of the bad reputation that multi-vis grade had in years past. However, that is no longer the case especially with modern synthetics.

[gilyZ06]

jdk, That would really piss him off!

[Subdriver]

Gily,
As No Doubt says, GM probably recommends the 5w30 as a compromise the meet the various conflicting requirements of temperature from Alaska to Florida while maximizing gas mileage.
The owners manual does say you can use 10w30 in SF Bay Area weather (I'm from Oakland), but recommends 5w30 anyways.

I switched to AMSOIL this year and become the forum vendor for it, via the link to the left:
<---------------

AMSOIL makes an excellent SAE 5w30 and 10w30 synthetic that compares favorably to Mobil 1.
Comparative Oil Test
AMSOIL vs Mobile 1 Oil Test

They also make an excellent filter:
AMSOIL Oil Filter Comparison

The exact AMSOIL applications for all your vehicles can be found here:
AMSOIL Online Product Application Guide

Thanks.


P.S. I personally use:
- AMSOIL Series 2000 20w50 Racing Oil for the engine as my car sees exclusive track use in the Mid-West high temps
- AMSOIL Synthetic ATF in tranny
- AMSOIL Series 2000 75w90 in diff

[gilyZ06]

Subdriver, Thanks for the imput. I am trying to decide between Red line and Amsoil for the whole driveline. looks like I'll go with 10w-30 or 10w-40 for the engine. Thanks also to the other replies. Gily