I think barely would be the answer. Most would be 20w by this milage. Even the 10w-30 shear fairly quickly and most of them are 20w by this point. If you need 30 weight consistantly you need a synthetic or a blend. I think I did see one UOA that has stayed in grade pennzoil I believe but other UOA on it showed the same shearing. The 15w-40 so called fleet oils seem to be the only dino's that don't shear. I know Delo comes in a 10w-30 so maybe that would not shear.
Sorry I wrote this before I saw you where concerned only with the low number. No knowledge but I have heard this does change with age also.
[ January 12, 2004, 08:37 PM: Message edited by: TR3-2001SE ]
I would imagine most 5w30s are actually 10w20s by the end of a 3000 mile interval. If you get the viscosity at 40c on your UOAs, that would give you a better idea of how the low end viscosity is holding up, and I'd be willing to bet most 5w30s end up with their viscosity at 40c being quite a bit different than the starting point. Wearcheck Canada and Wearcheck USA will give you viscosity at 40c if you ask for it (for no charge) so if anyone is running 5w30 dino and getting their UOA from them, be sure to ask for the 40c viscosity test.
[ January 12, 2004, 09:04 PM: Message edited by: Patman ]
I think you are asking about the longevity of the cold cranking ability, since you mentioned the 5W number.
This will depend on the quality of the base stock as to how much pour point depressants have to be added. Everytime you cold crank your car some of these will be "used up."
With dino, I would go into Winter with fresh 5-30. Yes, the cold cranking ability will degrade with time.
This is not so with synthetics and less so with Group III basestocks.