Question about oil weight

Keep in mind that one brand's "0w-30" probably doesn't have the same flow characteristics as another brand's "0w-30."

For instance, Castrol Syntec 0w-30 (aka German Castrol) is just about as thick as Mobil 1 0w-40 at engine operating temps, even though one is a -30 and one is a -40.

That being said, any oil advertised as a zero weight (0w) will be plenty fine for subzero mornings, regardless of brand.

 

Don't think so. Its CAFE. Read my post right before yours?

True, and also oil pressure and flow at normal operating temperature are almost completely dependend on that oil's HTHS viscosity, not the 100 deg. C viscosity. Not all publish HTHS, but it is available if you ask the maker.

The top graph shows measured oil pressure (and so flow) vs known high temperature high shear viscosities.
The bottom shows pressure vs published 100 deg C viscosity. There is only some correlation because higher weight oils tend to higher HTHS. But it is really the thickness in the bearings where the oil is "smashed" to a thin viscosity that controls the back pressure to the pump. The bearing wear characteristics are also dependent on the HTHS viscosity, not the 100 deg C viscosity.

(Graphs are mine, raw data painstakingly collected by the most excellent Caterham at bobistheoilguy.com)

 

The 2010 manual states 5w-20 and 0w-20 for the V6 engine. Says to use 0w-20 for cold starts and better fuel economy.

I'm currently using Mobil 1 Syn 5w-20, but just bought 0w-20 during the Advance Auto special last week.

Based on what I've read in the Bob is the Oil Guy and the Ferrari Chat link posted earlier in this thread I think the 0w-20 will be plenty for 97% of what I do. I pull a trailer occasionally, but nothing extremely heavy.

Not that either link is the gospel, but they state that "cold starts" are anything below engine operating temp. Which is your truck sitting in the summer heat or freezing temp. Obviously, the freezing temp is a tougher start, but you still get wear from the mid summer start up too. The 0w oils help protect against wear better at start up.

I've said before that both of those link never really quantify the numbers they provide. For example, what is the real difference between 0w-20 and 5w-20 at start up? Or 0w-20 and 0w-30 for that matter? Is it even enough to care?

 

I've got a 2007 so I'm stuck with the TSB guidance.

I've looked at the Mobil 1 spec sheets for their 0w20 and 5w20. The differences in viscosity (numbers) were very small but then what do I have to guage against. Soooo... IMO any practical difference at start-up is only worth considering if you park outdoors in Alaska or Canada in the winter and can't run a heater. And differences in fuel economy, whether at cold or hot temp running, would only be something you'd see in a fleet of vehicles; that obviously matters to Toyota who has CAFE requirements to meet. Or over a long operational life...something important to us but probably hard to quantify in order to feel good about.

But then I have read enough people claim clear economy improvements going to 5w20 in their older Tacomas that I'm gonna try it at my next change even though I'm skeptical. Since Toyota clearly endorses it's use, it can't hurt.

 

I got 5W30 on sale so that's what I've been using. This is the first winter for me using syn and I do notice no valve tick on AM start up and it was 17F this AM. Dino used to give me valve tick at 32F until warm up so just for that difference I'm happy.

 

Not in my opinion. Not according to the cold cranking viscosity numbers.
5W is a flippin' 5 weight. We used to run straight 20W all winter.