Question on oil weight?

Thanks for the info Mr. Incredible. I don't know if I will switch, I don't mind the 5k intervals since tires are ready to rotate among other things. We were so surprised with the increase in the guzzler Jeep it made me wonder if the Prius would respond the same. I appreciate all the info and everyone's willingness to share with us still a learnin'!

 

Actually, pour point has nothing to do with an oils cold temp pumping performance. Under SAE J300, pour point isn't even mentioned or tested.

Pour point is tested under ASTM D97. An oil may "pour" but still be far too thick to pump. It has been determined that once a Mini Rotary Viscometer viscosity of 600 Poise is reached or exceeded, the oil pump will cavitate

The only recognized test for low temp pumping performance is the ASTM D4684 MRV test, which sets 600 Poise as the absolute viscosity limit. For low temp cranking, the ASTM D445 is used as the CCS test

Let's contrast several "0W" oils from Mobil, as unlike the 5W-30, Mobil readily publishes MRV data on them. I run Mobil 1 0W-40 in my FJ, Mobil 1 0W-20 in my Prius, and used to run Mobil 1 0W-30 in my Prius

Mobil 1 0W-40: 26,242 cP at -40 C
Mobil 1 0W-30: 11,100 cP at -40 C
Mobil 1 0W-20: 5,642 cP at -40 C

Since all three oils easily pass the absolute limit of 60,000 cP, all three are appropriate as winter oils. It should be obvious that if you live in a very cold part of North America, the 0W-30 and especially the 0W-20 are far more appropriate

By reference, a conventional 10W-30 can exceed 100,000 cP at -40, and a conventional 5W-30 can exceed 70,000 cP at -40

 

According to the Sigma Automotive site Toyota is switching all of the Prius to OW-20 synthetic oil. I have discussed this with Toyota Service and they haven't heard this yet. Any thoughts on this? I understand that some people are getting 3-4 mpg increase when using this oil.

ENEOS Nippon Oil :: Sigma Automotive

 

Jayman, thank you for your copious information. It is quite illuminating. Being from Cold County I'm sure you've given this much thought.

I was mostly using the information I posted to illustrate the lack of a huge spread between 5w & 10w 30s. They are close enough to be interchangeable in most instances.

I wouldn't think a 10w-30 of the M1 variety would be a problem in Ohio for the next 5k miles.

do not know. The possibility exists of cavitation, but what are the realities of it and at expected temsp? To laypeople like me who are unfamiliar with the standards, numbers, test names, and tools you cite, I get most of it but with 10w's being the most purchased DIY oil you'd think problems would have shown up by now if they were lurking very closely to the surface.

Certainly I'm not saying to use 10w-30 under any and all conditions. What's best isn't what's in use, but one fill of M1 isn't going to kill anything.

 

Actually, based on MRV and CCS testing, there is a very wide spread in cold temp performance of conventional 5W-xx and 10W-xx oils. Synthetic 5W-xx and 10W-xx oils perform much better

The OP - xartis - originally stated he had filled with M1 10W-30. As you may recall, I stated that he should have no problem with that in Ohio winter temps. At -35 F, M1 10W-30 will still pump better than a conventional 5W-30

However, the OP ammended his information to state he had instead filled with a conventional 10W-30. As you will recall, I then changed my original statement and concluded he should change the oil to a 5W-30. Others have posted the Prius TSB that states a no-start condition, and a MIL, will be set if an oil too thick is used in the Prius motor in winter

Although generally true that most motors are able to cope with a wide variety of oils, the Prius motor is much more sensitive. There are TSB's from Toyota that caution about this, regarding oil viscosity and even fuel octane (Using Premium fuel may cause cold start difficulties in winter)

Actually, up here 10W-30 is only used in summer. Every winter, during our expected -40 cold snap, there are a rash of blown front seals when folks try to start their cars on gelled-up conventional oil. When you factor the cost of a tow, replacing the front seal, etc, it's far cheaper to just run a good synthetic in winter

Conventional oils also behave differently, depending on how the "cold soak" is performed. THis is due to the polymer additives in the oil. A rapid cold soak will generally have the oil perform close to its rated spec. A *slow* cold soak, say 48-72 hours or more - imagine leaving the car parked at an airport lot for a week - really buggers up conventional oils

As I have always stated, a person should match the viscosity to the expected ambient temp. You will generally cause little damage by running too "thin" an oil, even over extended periods. However, you can cause immediate and catastrophic engine damage running too thick an oil

I've never understood a person chosing a 10W-30 over a 5W-30. The 10W-30 offers no better "protection" over the 5W-30: at normal operating temps, there is little difference in viscosity

If you feel a motor can benefit from a somewhat thicker oil, there are a variety of synthetic 0W oils that offer the cold start protection of a 0W with better operating temp protection. Based on numerous oil analysis performed on my FJ, I now run Mobil 1 0W-40: this oil meets tough extended service, severe duty specs in the EU under ACEA A3/B3-B4

A good choice in a 0W-30 is Castrol Syntec, their 0W-30 is the only Syntec I'd use. It's actually made in Germany, approved for current Mercedes and older VW specs. It tests out on the thicker end of the 30 spectrum.

As previously stated, the OP changed the information provided. He did not fill with M1 10W-30, he filled with a conventional Mobil 10W-30. That is why I changed my opinion and told him to change the oil. I originally told him to leave the Mobil 1 until the next oil change

 

I run Mobil 1 0W-20 year round in my Prius, due to the excellent used oil analysis results up to 16,000 km. In summer, I've never noticed any difference in fuel economy. In winter, perhaps 2-5 mpg

 

No, it is not

 

Jayman, I missed the part about syn turning into conventional. The hazard, perhaps, of trying to post while trying to get work done. I should pay better attention to the posting, rather than the much less important work. My apologies...

Being an old(er) buzzard with much experience but being a Prius newb, Been Around A While is bound to bump up against Modern Technology. I confess I had not noticed the no-start condition related to cold and oil. Such a weak sissy motor that can't start its way out of a cold paper bag...I can hardly imagine it. It will take some getting used to, for sure.

Not having been privvy to the standards and numbers of which you speak, I can't really say whether you are holding up the golden specifications that relate to the real world or not. It sounds good. I guess the difference you cite between standard 5w & 10w 30weights becomes a real issue at lattitudes I don't visit and with Barney Fife motors I never operated until now.

I will review further, and I thank you for your information.