Thinner motor oil?
 

Yesterday I went on a hunt to see if I could find any of the discontinued Honda Green Oil, which is what Honda recommended and was putting into Insights, HCH's and CR-Z's in Japan. I remembered reading about it a few years ago, that it doesn't have an SAE rating but was probably thinner than 0w16, definitely a lot thinner than 0w20, but it seems it's basically all gone at this point. One source said after Green Oil was discontinued, Honda was recommending the use of Castrol Edge, and that it was thinner than most other 0w20's.

A look on Amazon showed Ravenol sells a 0w16, though it's pretty expensive at ~$40 for 4 liters, as compared with ~$25 for 5 quarts of Mobile one 0w20. However, I live in a cold climate (winters down to -40 sometimes), and I'm considering trying it.

This was a good read:

http://www.ravenol.de/fileadmin/cont..._0W-16__en.pdf

Some further googling revealed Honda has an oil called "Ultra NEXT" in Japan which is recommended for their Earth Dreams engines. It's apparently equivalent to something like an ~SAE8, but has no SAE rating on it either.

http://www.fitfreak.net/forums/3rd-g...800-miles.html

Anyone know where I might find some Ultra NEXT? Or, does anyone have any experience with Ravenol's 0w16, especially in colder climates?

Apparently you can buy NEXT oil here, but they don't ship to the US:

t-joy | Rakuten Global Market: HONDA (Honda) genuine oil ultra NEXT 4 l (08215-99974)

If no one on here knows try bitog.com
I stay away from the super thin stuff.

For what it's worth, I've only ever put 0w20 in my engine and it hasn't burned a drop of oil in the 60,000 miles I've owned it. Every 7-10,000 miles 2.6 quarts come out, and 2.6 quarts go back in. I also have dealer records to suggest that the previous owner only ever had the oil changed at the dealer, and that they used Honda-approved 0w20 or equivalent syntheic oil. Using thicker oil is not recommended by Honda, especially in colder weather, because the tight clearances in the bearings would prevent proper lubrication at typical operating temperatures, much less before the engine is fully warmed up. The 0w20 we can get in the US is a lot thicker than the oil the Japanese have access to and run in their engines.

If you have any where near 100,000 on the engine those tight bearing clearances likely don't exist any more.
On my 8L engine I got the rod and main bearing clearances right at about 0.003 inches and I plan on running 10w-30. Industry standard for bearing clearance is between 0.004 and 0.006 and never less than 0.002 inches. Less than 0.002 the engine will sieze when you first start it up.
So I don't really believe the "tight tolerance" thing because no mass produced engine is going have bearing tolerance as tight as a blue printed race motor.
Manufacturers just don't have the time or money to pay some one to stand around for hours squishing plastigauge and swapping bearing halves on each engine intended for an economy car.

Sure, but do they have equipment that will let them reliably make parts to those tolerances, so that every bearing is e.g. 0.0003 +/- 0.00001? Or even automated measuring equipment, so no one has to stand around squishing plastigauge? Certainly that's technically possible with laser measuring equipment, though I've no idea whether it's economic.

According to their respective websites:

Castrol Edge 0W-20: 8.57 cSt@100C
Mobil1 0W-20: 8.7 cSt
Vavoline Synpower 0W-20: 8.8 cSt
Pennzoil Gold (synthetic blend) 0W-20: 8.3 cSt
Pennzoil Platinum (full synthetic) 0W-20: 8.3 cSt
Quaker State Ultimate Durability 0W-20: 8.3 cSt
Honda (European) 0W-20: 8.2 cSt

Additions 11/08/2016:

Chevron Havoline synthetic 0W-20: 8.5 cSt@100C
Toyota Genuine 0W-20: 8.5 cSt
Amsoil OE Synthetic 0W-20: 8.3 cSt
Amsoil Signature Series 0W-20: 8.7 cSt

Pretty sure there are diminishing returns with going thinner right? On ft86club.com people say that 0w-20 is so thin that at track temperatures of like 260F none of the oil is being bypassed anymore as the pressure is only in the 50psi range at 7400rpm.

We're talking 8.7 vs. 8.2 cSt. I never read up on how units work but that can't be a big difference. If it drops your oil pressure 1psi, that might get you like 0.1% more mpg. A 30 weight oil is around 10-11 cSt at 100C, and the fuel economy gain from going from 30 to 20 is very hard to measure.

The gain is mostly in the thickness when cold.

The 8.* cSt was measured at 100°C.
But even the 0W20 oils have a thickness of more than 40 cSt at 40°C (104°F), that must be over 100 cSt at a cold winter start.
The first digit is more important than the latter. I'd rather use 0W50 than 5W20.

I wonder if "0w16" might not be thinner at cold temperatures than, say, 0w50, there's just no easy way to advertise it since they've already hit zero?

Anyway the gains seem to be enough that Honda and Toyota are chasing making thinner oils available.

EDIT: The Ravenol 0w16 on Amazon is rated at 7.24 / 38.36, as opposed to 8.7 / 44.8 (100c/40c). I'm going to poke around and see if I can find any numbers for green oil and NEXT.

EDIT2: Apparently Honda's Green Oil was rated for 8.154 @ 100c and 32.1 @ 40c.

EDIT3: This thread on botog has a Blackstone analysis of the NEXT oil, that claims 5.13 @ 100c and 20.844 @ 40c.