Castrol is a GroupIII. PAO's are a GroupIV.

Ken

Just a little note on the Shell Helix. Ferrari specifies this oil for their engines. Let me just say this, I don't know of a single Ferrari Tech who recomends this oil. It has a very bad habbit of foaming. The Ferrari Challange guys found this out years ago with fluctuating oil pressure, and no longer use it. The oil is not well regarded in the Ferrari community, and I won't run it in my car.

BTW, Shell is Ferrari's largest sponsor in F1.


Darrell.

Ken, you are correct- I keep getting the two confused. PAO's are typically the better oils, and they are Group 4. This terminology gets mixed up all the time.

Mobil 1 VTwin 20W-50..

Ditto that. Get your wallet out though.

Which Viscosity to Use?
On the other hand, we can't see (in oil analysis) where it hurts anything to run heavier 10W/30s or even 10W/40s in modern automotive engines. The heavier oils provide more bearing film, and that's important at the lower end. If your oil is too light, the bearing metals can increase. If the oil is too heavy, the upper end metals can increase.The trick is to find the right viscosity for your particular engine, which is why we suggest following the manufacturer's recommendation. Same is true in marine engines. Too light or too thick will cause extra wear on the upper or lower critical parts of the engnie.

Merc's 20w-40/Mobil1 15w-50/V-twin20w-50/40wtetc...

Automotive applications and marine applications are totally different as we know

Merc's Synthetic Blend for outboard or outdrive setups is a great oil. I would sure us it if I wanted an upgrade and not void a warranty or have any wories.

25w-40
[http://www.mercurymarine.com/otherpr...verado.phpurl]

25w-50
http://www.mercurymarine.com/otherproducts/maintenance/mercruisersynthetic.php[/url]

496 Mag / 496 Mag HO...
87 Octane recomended, or 89 if thats the lowest grade at the docks... Change the oil and filter every 40hrs or at the end of each season.

MERCRUISER (25W-40) ENGINE OIL
Specifically formulated and developed to meet the needs of:

High-output sterndrive and inboard engines.
Multi-viscosity 25W-40 oil formulated to eliminate thermal breakdown (no viscosity improvers necessary) under extreme temperatures and loads.
Field-tested and proven in gas and diesel applications.
Provides superior lubrication and protection of internal components from corrosion, wear scuffing and scoring - even in higher temperature engines.
Provides warranty protection for Mercury MerCruiser engines.
Available container sizes: Quart, Gallon, 55 Gallon
http://www.mercurymarine.com/otherpr...mercruiser.php

Mercury 25w40 or 25w-50 semi syenthincs are the way to go for those who want to "stay in documented warranty" and are not sold on fully synthetics. Merc says with 40hr changes.

In my opinion the 25w-40 is good up to 80* temp and the 25w-50 ought be used beyond that or for hard running.

Racing calls for super premium synthetics...v-twin...racing RP and Amsoil.

My .02

You are allowed to use whatever oil you want, as long as it meets or exceed specs, without voiding any warranty. Its a federal law.