Spring, Summer and Fall I use Mobil 1 15W50. Winter I use 10W30, Im in Central Kentucky. Winters here rarely see teens, mostly mid 20's and above.

Oil weight definitely depends on where you live. Although, I think the Chevy V8's like the heavy weight oil whenever they can use it.

 

some tests have shown that you wont see the benefit of synthetic until 5K miles because it really does last a bit longer and provide protection...

 

Royal Purple 10w30

 

Royal Purple is better.....can not be beaten by anything

 

actually, here in Houston I have about 8 engine builder friends.. All make cars faster than 9sec (people like Lawrence Connolly) and all say stay away from Royal Purple. It leaves a residue and a buildup..


I wouldnt touch it and its made not far from here...

 

Mobil 1 5w40 "SUV"

 

I too run Royal Purple 10W/30.

SteveC

 

Both.

Synthetic means that the BASE oil is a PAO oil. (Manufactured in a lab from a form of alcohol.). This oil is truly a paraffinic structure = a good thing.

Crude oil is typically mostly an aromatic structure which is a BAD thing. This is why we have refineries. They use hydrocracking to convert the Aromatics to Paraffinic structures.

Synthetic oil is a perfect paraffinic base oil to start with then they add the additive packages to it.

So to answer your questions the Synthetics will not typcially oxidize and breakdown as fast; and the Viscosity Index of a Synthetic is much more stable across temperature and with age of the oil.

Now just because you have a Synthetic base oil you still have to have a good additive package to go along with it. A refined oil with a good additive package is better then a Synthetic oil with a crappy additive package. But all things equal the Synthetic is a much better choice.

I change my 01' Blazer every 15,000 miles. I save money and provide better lubrication for my engine. It's a win-win situation.

EDIT: I use 10w30 Mobile 1

(And be careful out there too, companies can now call their oil a synthetic if it is a Group III oil = highly refined)

Mobile 1 - PAO Oil
Amsoil - PAO Oil
Royal Purple - PAO oil

The Castrol Synthetics and other brands are NOT PAO oils, but Highly refined crude oils enough where the feds say it's ok to call a Synthetic (But keep in mind - NOT PERFECT).

Interesting Quote:

"In addition, BP Amoco Chemicals’ Svoboda says, “We have seen some tempering of growth for PAO in North America. We attribute this to the increasing availability of Group IIIs. However, on an international level, PAO demand continues to grow at a rapid pace. PAO in Europe is more than double that of North America. Europe continues to be a strong growth engine for PAO. This is based on the European OEM (original equipment manufacturer) drive for higher performance and by environmental considerations, such as emission reduction and extended drain intervals.” He agrees with Pernik that the PAO market remains strong in Europe and that eventually the rest of the world will follow the higher performance requirements established there.

The primary downside to the NAD ruling and any resulting replacement of PAOs with VHVIs, says Svoboda, “is that North American PCMO consumers will not be getting the higher quality performance level offered by the PAO. Despite claims of equivalent performance, PAO continues to maintain its superior performance over Group IIIs under extreme operating conditions, particularly with regard to low-temperature performance and high-temperature oxidative stability.”

 

I would think that "Red Line" is a PAO oil too.

SteveC

 

Yes, that's one I forgot.

 

That's what I've run in the Z since getting it in November. Though I'll probably switch to Mobil 1 10-40 since the GOOD Castrol stuff is getting harder and harder to get.