0w30

A good compromise would be to change the oil after 5,000 before the winter cold weather starts.

 

Yes, I agree with xpcman's advice. Which OW-30 oil did you install?

 

0w30 synthetic is fine for 10k.

It may not be the preferred oil but it will do a great job.


iPhone ?

 

I have looked all over the web for information on WHY 0-20w syn oil is so important and have not found anything. I'd like to know what will happen to the engine if this weight is not used? Why is 5-20 or 0-30 not recommended, what will happen if they are used, can anyone make a statement on the pros and cons for the oil issue? There has been enough time for the Prius to be tested, I've owned one since late 2003 ( a 2004 model) and nowhere have I found info.

 

Nothing will happen except a small increase in fuel consumption that you might not even notice. Toyota got it's government mileage rating using 0W-20 oil so they have to encourage owners to use 0W-20 oil. The viscosity requirement really is that simple.

Synthetic is required because of the 10,000 mile oil change interval.

I believe that in some other countries Toyota gives you a choice of viscosity.

 

XS650, speak up where you disagree. On the cold end, 0W-30 oils are typically thicker than 0W-20 oils (by cSt at 40°C and MRV/CCS), but is it thick enough to increase engine wear? Probably not. On the hot end, most 0W-30 oils will rarely, if ever, get hot enough to thicken to a 30 weight, so this is a non-issue, too. Thicker oil does increase friction, hurts mileage slightly.

 

Hi Bruce, good to hear from you. When did you move to OKC?

Most engines get to oil temperatures of 100C+ under normal operating conditions so 0W-30 will act like a 30 weight when the oil is up to normal operating temperatures. That said, Prius engine oil should run a bit cooler than other engines in traffic because the engine is off so much of the time, on the highway though it should run about the same as other cars.

One way to put the viscosity differences in perspective is to look at how much you have to change the temperature of the oil to make two oils of different SAE viscosities have the same actual kinematic viscosity in cSt. It only takes a difference of about 15F at operating temperature to make the kinematic viscosity of an xW-20 and xW-30 the same. We would need the manufacturers specs or lab tests including viscosity at 100C and viscosity index and a viscosity calculator to determine the exact temperature difference, but it usually falls with the 10F to 15F range.

 

If your car does 1mpg less with the 0w30 oil (and i'm not saying it will) at say $4.00 a gallon for fuel and assuming 50mpg with 0w20 oil. In 10,000 miles the extra fuel used would cost you $16.00. However in the UK with fuel at close to $10 a gallon it would cost $40.00 extra so would be cheaper to change the oil.

Grumpy Cabby found this when his gen3 had the wrong oil put in by the dealer.

 

$10 gallons do give you a different mind set.

 

Thanks everyone, I knew there was some reasons behind Toyota recommending 0-20 and I'll go along with the idea that Toyota tested with 0-20 and liked what it saw. I've got 0-30 in mine now and will be taking a 3 week road trip so I'll see if the MPGs suffer. As hot as it is I don't see a problem with 0-30 but if I do I'll dump it and go with 0-20. Even with the 10k oil change period, I always change around 6 or 7k, it's easy to do and takes me only about 20 minutes.

I average 55mpg and this will test the 0-20w and 0-30w challange. Three week road trip coming up on the 14th of next month so I'll find out which weight wins, and will let everyone know.

I put Mobil One 0-30w syn. I'll be able to tell how she performs wheather 0-30w works as well.

 

No big deal ... next time use 0-20.

REV

 

xs650, I've always been in the OKC area. I'm Bruce T on BITOG. You're probably thinking of bruce381 the formulator, who is considerably more knowledgeable about oil. By the way, what happened to the original poster?

I'd be surprised if the oil is hitting 100°C very often, but I haven't seen any data on Prius oil temps. My coolant temps are only 91-94°C (196-201°F) on long highway drives at 100°F, although the oil temps could easily go higher.

 

I was thinking of the formulator.
Oil temperature typically runs higher than coolant temperature. It depends on engine design and operating conditions, but on cars without oil coolers I normally see oil running around 15 to 30 degrees hotter than coolant once the engine is up to operating temperature. Oil pick's up a lot of heat from the cylinder walls and also gets heated a lot as it get sheared in the main and rod big end bearings.

 

That makes sense that the oil temps in most engines would eventually rise higher than the coolant. I'm working with a combination of impressions, but no actual data. I remember Terry Dyson once telling me that hybrids all have low operating temperatures. Also, I saw a post on BITOG from Silber Igel saying his Camry Hybrid's oil temps only hit 152°F:

Prius and Synthetic Oil? - Bob Is The Oil Guy

Ah, now I know why his oil temp sounded suspiciously low. He was taking an IR reading off the dipstick.

 

Yes but, further on in that thread he says he was using an IR thermometer to measure the temperature of the tip of the dipstick after he stopped. Gen Polk in that thread got considerably higher temperatures by measuring the temp of his HyCam oil pan. That's a better way to do it, but will still give reading considerable below actual oil temperature in the sump. Anything short of a temperature probe in the oil inside the sump will give a low reading.

 

Good catch, I missed ekpolk's comment about measuring 175-185°F at the oil pan after shutdown. Yes, anything but a real-time oil temp sensor in the sump isn't going to give accurate peaks. I've noticed that my coolant temp drops very quickly once I back off the high rpm and exit the highway (typically from 198°F to 189°F). The oil temp should drop quickly, too.