WHATS THE BEST OIL? 0W20? GOOD?

Patrick

Good points. Again, I find it interesting that EU market Toyota's are "allowed" up to a 20W-50, but a 5W-30 is prefered. Not that I am suggesting a 20W-50 for everyday use

I've had very good results with M1 0W-40 in my FJ, so based on the used oil analysis will continue to use it. M1 0W-20 appears to work best for my Prius, but YMMV

There are many interesting differences in oil change intervals and recommended viscosity, when one compares EU market to North American market. I travel extensively to the EU on business, and their large city commute is just as bad as ours can be. I've been to Kiruna Sweden a few times, their climate compares to Thompson, Manitoba.

I still believe in matching a viscosity to the ambient conditions. With modern engine designs, there is little to no need for a xW-50 oil. Some motors, like the V6 in my FJ, appear to benefit from a light-duty 0W-40. I still find it amusing that I was one of the first in this area to use the "water thin" 0W-30 as a winter oil, with very good results

If you enjoy maths and good technical reading, I've attached some interesting technical articles

jay

 

What quantitative measure shows that 0W-20 works better in your Prius than the recommended 5W-30? Yeah, I know, it's cold in Manitoba in the winter, but after ten minutes or so it's not very cold inside the engine. If it ever seizes don't come crying to us :_>

 

The used oil analysis that I do on my Prius. Wear metals and nitration improved with M1 0W-20, compared to M1 5W-30 and M1 0W-30. M1 0W-30 had better wear metals and nitration compared to M1 5W-30

 

Hi Jay,

Thanks for providing the articles.

Hi Richard,

I asked Ken (@Japan) about this. He was kind enough to provide a link to the current JDM Prius owner's manual. This goes beyond the little excerpt that Jay provided, and shows 0W-20 is recommended for all ambient temperatures, at least in Japan. See page 5 (out of 9).

So - I now feel better about 0W-20 being used in hot weather.

 

Patrick

Thanks for attaching the Japanese market manual. I know a person who is fluent in speaking/writing Japanese, I will have to bribe/coerce him to translate!

jay

 

Here is a JDM 0W-20, ENEOS - manufactured by Nippon Oil.

It is now available in the USA. In fact some Toyota / Lexus dealerships are now carrying it.

www.eneos.us

 

Count me in as one of those switching to 0W-20 oil. The fact that Toyota back approved that 20 weight oils for their engines (Prius excepted) and that the Japanese Prii are specified to use such oils and that the used oil analysis's show good wear with 20 weight oil all convinced me to go to 20 weight.

Our car is used as a "mommy" car and is subjected to mostly short length trips in which the engine spends are larger than usual time below operating temperature. That first five minute bar is a larger chunk of the trip and takes a big bit out of our MPG. I hope, especially in the colder months, to see some small improvement going to Amsoil 0W-20 over the current Mobil 1 5W-30. Approximately 400 miles to the next oil change so we shall start the 20 weight oil run soon.

Rumple

 

My hypothesis for why Toyota has held the Prius to 5w-30 is fuel dilution. I've seen fuel in my Prius' oil on several analyses, and a couple other members over at BITOG have had gas in their 1NZ's oil too. But some Prii don't. And obviously, my hypothesis does not account for the different spec for non-US cars. That said, I think they may be worried about a few extreme dilution cases in which the use of a 20 wt oil might actually result in oil sufficiently compromised by viscosity reduction that engine damage is possible or even probable.

Again, it's only a hypothesis, to be ultra-clear, I'm not offering this as settled fact. There is also a member at BITOG who has been using 0w-20 in his Prius, and his wear metals were all well within acceptable ranges. Who really knows...

Rumple, if you do go the 0w-20 route, I'd respectfully recommend that you try at least one UOA. It's very easy to do (if you haven't tried it before), and it will at least let you know if your Prius appears to be a diluter, and if it is, whether there appears to be any impact on the lubricated parts.

 

Thanks, I was indeed going to do a UOA at 5,000 miles. I posted a UOA at bobistheoilguy.com for the last changeout on my Prius found here - it was the ??? dealer oil at ~5,200 miles (I thought it was ~6,000 but looking back it that was an overestimate). Luck for me there was no fuel dilution issue at that time for my Prius.

 

Rumple:

As dcoyne, another Prius owner, pointed out, while Blackstone does do quality work, they do for whatever reason, seem to under-evaluate fuel in oil. Terry Dyson's lab has shown fuel in oil where Blackstone has not. Of course, maybe it Blackstone who's on target... But with this engine, I'd at least be careful and not assume no fuel in the oil. At any rate, it's not as if a 20 wt will be an instant problem, just keep your eyes open see how your car responds. And do please let us know how it works for you.

 

Rumple:

To expand some on my last post: the concept here is that in theory, for each engine out there, there is a threshold of oil viscosity after which engine damage will begin to happen (this applies to both the thick and thin ends of the viscosity spectrum). Without doubt, the car makers build in very substantial buffer spaces between the ultimate limit on both ends, and what appears in the owner's manuals. We have a member on BITOG who ran a fill of -- get this -- 0w10 Royal Purple for about 3k miles in a 2.5L Nissan Sentra, with no apparent problems. Wow. Now, OTOH, I have no idea where the boundary for a Nissan 2.5L I-4 really lies. Maybe those engines would be fine with any oil at 5.0 cSt or above (doubt it, but who knows...). Or maybe this fellow was right at the edge of his margins, and showed no harm because although at the line, he never actually crossed it.

The issue here (or one of them anyway) is that the Prius does have a track record of contaminating its oil with fuel. Not surprisingly, if you put enough gas in your oil, the viscosity will start to decline. But for any given engine, no one can be really sure where the critical point at which engine damage begins, lies. Frustratingly, yet predictably, Toyota has not been good enough to share any of their data with their customers (incidentally, there's not a peep about fuel dilution in the Prius on TIS, least not that I've seen...). So we're left to accept their "presumptive" oil prescriptions. I don't think that any-w-20 in the Prius is a "recipe for disaster," but if you do decide to go that route, I'd strongly recommend that you do your own UOA to see how YOUR engine, under YOUR operating circumstances is holding up.

Good luck with it!!!

 

I'm a strong advocate of used oil analysis. At least with my Prius, no fuel dilution issues.

The oil analysis has picked up something odd with my FJ. It's "hard" on oil, very high nitration. That's something you wouldn't pick up unless you had your oil analysed

 

Well, huh. I can't argue with that. So why do they recommend 5W-30 in NA?

 

It's about availability.

0W-20 was not readily available - until recently.

Most Toyota & Honda dealerships have 0W-20 available in quarts.
Now, some dealerships have it available in bulk. Primarily through Nippon Oil - ENEOS (www.eneos.us)

My local Toyota dealership offers a 0W-20 oil change for $44.
But, you have to specifically ask for it. Otherwise you may get 5W-20 or 5W-30.

 

skoh:

I'm sure that they've considered availability, but I don't think that explains the 5w-30 recommendation. 5w-20 has been widely available for a least a decade (it's been almost that long since Ford and Honda took the plunge), and if not "widely available," was still easily obtainable for years before that.

If the basis for the NA 5w-30 rec was a lack of access to 0w-20, but 20 wts were still issue-free for the Prius, why would they not simply recommend 5w-20?

The availability issue is also not consistent with TSB EG018-06 (citing from memory, that may be the wrong TSB ... I'm referring to the one in which Toyota announced almost all cars, minus the Prius, were going to 20 wts). If 0w-20 availability were a problem, why would Toyota release a TSB recommending it, or 5w-20, for almost all its new cars, and yet, still tell us not to use it in the Prius?

 

Looking more closely I see that the Japanese manual recommends (or allows?) 0W-20, 5W-20, and 5W-30 for the same ambient temperature range (from below -30'C to above +40'C). So it's all good.

 

Richard:

While I certainly don't believe that use of anything but 5w-30 will cause the immediate destruction of a US Prius, I wouldn't go as far as to suggest that one can go ahead and use the oils spec-ed elsewhere. First, Toyota went to careful and considerable lengths to distinguish the US Prius' oil spec from the others, while at the same time, moving almost all their other cars over to 20 wt oils. I'm left wondering if there's something about ECU programming, the PCV system, or something else going on that makes the US version of the car a risk on 20wt oil. If not, why go to the trouble to set the car apart from all their other products.

I just wish that Toyota would step forward and eliminate this mystery...

 

ekpolk, thank you for rescuing me from my backsliding. I agree: we do not know why Toyota recommends as they do, so the only safe course is to RTFM and do what is recommended for each region.

 

I agree. I do not speak for Toyota. But, my personal opinion is that they would prefer to go to lower viscosity for the incremental fuel economy benefit.

They had the same situation for ATF. Originally they specified the Dexron/Mercon III because that is what was widely available in NA.
Now, everyone has their own fluid.

And there is the same trend to lower viscosity in ATFs to promote fuel economy. The more recent GM Dexron VI, Ford Mercon LV, and Toyota WS are all low viscoity ATFs.

 

That means I sure don't want it in *my* crankcase. Not until dealerships use industry-standard bulk lube contamination control.

Des-Case Corporation

That means a proper desiccant breather, not a simple inverted pipe with a screen