0W-20 vs 5W-30

[Spart]

5w30 is only good down to -30c...lol, actually my uncle recommends putting 10w30 in everything ...my 12 odyssey also calls for 0w30 and its about 120k miles currently, been doing amsoil for last 50k

I mean, sure. I used to run 5W-30 in my Tacoma.

I run 0W-40 now and it turns over noticeably easier when the temps are around -10°F. Sounds smoother when it's hot, too.

And no small thing - I did UOA before and after switching to 0W-40 and my wear metals are consistently down by half.

Again, most 0W-40 will shear to the point that they have the viscosity of either a thick 0W-30 or just barely are in range for 0W-40. I don't look at this as a bad thing if you know what you're getting. If it protects the engine better in the cold and when its hot, that's a win-win.

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[ashmostro]

Agreed. And knowing that "wider" winter-summer viscosity range oils will degrade faster than narrower ones, just lower your OCI's. Simple, and better overall protection in all thermal conditions.

Example: I am running 0W-30 and plan to do 3-4k OCIs. The other advantage of this is your additive package stays more consistent as you aren't changing weights twice a year.

 

[Spart]

Agreed. And knowing that "wider" winter-summer viscosity range oils will degrade faster than narrower ones, just lower your OCI's. Simple, and better overall protection in all thermal conditions.

Example: I am running 0W-30 and plan to do 3-4k OCIs. The other advantage of this is your additive package stays more consistent as you aren't changing weights twice a year.

0W-30 is probably a great choice. If you don't ever track the car in hot weather, it is very likely all you need year-round.

Like you mention, it's about suitability for a wider range of thermal conditions.

Some people balk at running a thick oil in a car that calls for 5W-20 or 0W-20. Let's ignore CAFE for a moment and also ignore the fact that the UK owner's manual for this engine in the Civic Type R also specs 5W-30 and 0W-30.

The reason that's often given to not run thicker oil is that the engine somehow isn't designed to run on it. You'll hear "modern engines have tighter tolerances" and musings about the variable valve timing needing a specific viscosity of oil.

It is complete and utter hogwash. First of all on the tighter tolerances, I liken the Coyote/Voodoo/Predator engines to a modern V8 Honda engine because of their power curves and overall design. Dual overhead cam with variable valve timing on both exhaust and intake, and the Voodoo has essentially an AP2 Honda S2000's torque curve.

The Coyote calls for 5W-20 in the US (or at least the S550 used to, I'm not up to speed on the S650.)

Roush will take that engine, slap a supercharger on it, and replace the oil cap marked 5W-20 with one marked 5W-50. They change nothing about the internals, not even the oil pump gear.

Then you have the Voodoo and Predator engines which have 5W-50 spec from the factory. Do they have "looser tolerances" in order to run a thicker oil? Absolutely not. The clearances are the same.

What they have is a gas guzzler tax and low volume production, so Ford can spec an appropriate oil weight for their expected use case that gives them a wider thermal operating envelope.

As for variable valve timing systems that rely on oil pressure, what they need is a minimum oil pressure in order to run properly. They will not fail suddenly because you have an extra 10psi. In fact, I can talk your ear off about certain older engines with variable valve timing that experience common failures where the solution for future longevity is a high volume oil pump.

All this is to say that we have collectively forgotten what it was like before CAFE when manufacturers were free to specify many different weights of oil dependent on ambient temperatures.

I'll give a modern example: this is the oil viscosity over temperature chart specified for the Toyota 2GR-FKS out of an Australian owner's manual:

If the engineers had their way and also didn't feel the need to dumb things down, something similar to this would be in the owner's manual of every combustion-engined car on the road today. And particularly with cars that are marketed as being track-capable, they'd have recommendations about specific fluids for track use as well. Engine oil, trans oil, brake fluid - the whole lot.

 

[bvanlieu]

The issue to me (from sampling 5K runs a few times now) is fuel dilution, it is there on our car and really any DI engine. That's the main reason to have a bit more starting viscosity, especially if you are running extended drain intervals.

Note: the tech in todays blends and high quality VIIs used, doesn't mean a 0w30 is worse then a 5w30 anymore either, the base stocks to have a 0w30 can be a tad better, more PAO etc...so really don't go by that, go by what is a good oil for your application.

Side note: tolerances don't change. Example, the bearings in a B58TU2 are exactly the same from the introduction several years ago with the X7 (where 30 grade was in the manual) to our 25 we got this year that says, ahem, 0w12. You can do the same exercise with a SBC, Ford 5.0 and a slew of other engines that have seen grades go down in the US only manual.

You can guess what my preferred grade is in the 400HP monster for 7-8K annual OCI

 

[jolasteddy25]

Agreed, first oil change at 4k miles last week and used Amsoil signature 0W-30 with Amsoil oil filter.

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