Does anybody know if it would hurt to run a heavier weight oil to gain some oil pressure? I run a heavier oil in my old V8 s10 but I wasn't sure how these newer engines would handle it. I know the owners manual says not to use anything like a 20-50w.

 

in the old days thicker weight oils were favored by racers. the theory was heavier weights gave higher film strength and better boundary layer lubrication.
Today the racers use 0W30 the lighter oils get lubrication to and heat away from the critical surfaces quicker.
todays lubricants especially the synthetics don't need high viscosity to work.
Stick with a quality 5W30 synthetic that meets the GM spec

 

What is 0w30? Is that like a straight 30 weight oil? Right now I use Mobil 1 10w30 and my oil pressure is about40 to 50 going down the road and 28 to 30 at idle. Thats after I have been driving for a while. Fully warmed up.

 

An oil is rated at normal operating temp (the second number, e.g. 30 weight), as well as a "cold" rating (the first number). A 5w30 is actually much much thicker cold, though only a 5 weight, than when hot when it meets a 30 weight standard. As oils go, Mobil 1 tends to run at the low end of the "hot" 30 weight band. Other oils, such as AMSOIL or German Castrol tend to run at the upper end of the 30 weight band, nearer a 40 weight.

These AMSOIL products meet GM Standard 4718M for the C5/Z06:
AMSOIL Series 2000 0w30
AMSOIL SAE Synthetic 5w30

In addition, the AMSOIL SAE Synthetic 10w30 also meets GM Standard 4718M.

You can see the hot (100C) and cold (40C) viscosity of the AMSOIL products on the links above.

 

for a 95k, can i use 10/30?
thanks

 

If you mean a C5 Vette that has 95k miles, then yes, though I would point out that the owners manual for the C5 recommends a 5w30 over a 10w30. However, many 10w30s, such as the one I linked above do meet the appropriate standard for the C5 and may be more suitable for summer time use, or for those who live in FL or Socal.

Keep in mind that a weight rating of an oil has two parts, the first number, which is the "cold" rating (you can think of the "w" as Winter), and the second number is the "hot" rating. It is a common misconception, that a 5w30, or a 0w30 is thinner at normal operating temps than a 10w30. All three of these fall into the same 30 weight band when "hot", or about 212F, which is essentially the vettes normal oil temp. It is also a fairly common misconception, that the oil is thinner when cold than hot as the cold number is lower, e.g. 5 vice 30. Many people will say that a 0w rated oil is too "thin" when cold and won't protect your engine. Actually, the opposite is true, the ratings are just different cold than hot. A typical multi-viscosity 0w30, or 5w30 is about five to six times more viscous (thicker) at 100F than at 212F.

However, taking this a step farther, if you actually look at the viscosity rating of an individual oil, you will see that 30 weight is a band, and oils can be lower or higher in the band, but still be a 30 weight. In general, a 10w30 will be higher in the band than a 5w30, so while both are 30 weights at normal operating temp, the 10w30 may be a little thicker. However, this is not always true. Based on the current product data sheets, Mobil 1 5w30 is actually thicker at normal operating temp than Mobil 1 10w30. This also varies by brand as well, so you can't really compare one against the other unless you look into the actual viscosity ratings.

To demonstrate all of the above, here are the "cold" (40C) and "hot" (100C or 212F) viscosity ratings for several AMSOIL oils and Mobil 1 oils based on the current product data sheets (ranked from lowest to highest "hot" viscosity:
Oil / Cold Viscosity / Hot Viscosity
Mobil 1 10w30 62 10.0
Mobil 1 0w30 56 10.3
AMSOIL 10w30 59.2 10.6
AMSOIL 0w30 56.9 11.2
Mobil 1 5w30 64.8 11.3
AMSOIL 5w30 64.3 11.6