I searched but still curious, what viscosity oil are you running in your Gen II?

You are correct. I tried using Toyota 0W-20 synthetic on my 2004 but the engine started to consume a noticeable amount of oil so I went back to 5W-30 synthetic.

If your engine has low enough miles so it will not burn oil, I would say that 0W-20 will improve 2G mpg ~5% or more esp in the winter. I'd be cautious about using that very thin oil if your ambient temp exceeds 100 degrees F.

 

I subscribe to the view that in most cases the manufacturer knows best. So I use 5w-30.

 

I had oil left over from the anti-Prius (2001 Nissan Pathfinder), and was adding 1 litre of it at each change (10W30 Mobil 1) the rest being 5W30 Mobil 1. This summer I accidentally put in only 10W30 oil. I was too lazy to drain and correct. I noticed no difference in mileage. I did notice rougher starts and stops when cold. Once warm there wasn't (and shouldn't be) any difference. Switched to full 5W30 last month. Again, no mileage difference noted. Pearl does now start and stop much more smoothly.

 

5w-30 as recommended.

 

0w-30

 

Now your making me nervous. Is 0W-30 OK in a Prius? I've used it since about 5k and have 62k now. The car does not burn oil between changes (5k intervals). By my temp. gets in the upper 90's all summer. Am I going to hurt my car?

EDIT: I use Mobil 1 oil.

 

Just had oil changed Monday. I bought my own oil and filter and had my usual mechanic change it for me (my ramps are too steep for the Prius). Told him to only put in 3 qts and I would top-off as necessary after running the car for a while. After checking it each day for 3 days, I note that the level is about 2/3 the way between the low/high marks.

Went from whatever dino-oil the dealer put in last time to Mobil 1 5w-20. I intend to change it again at about 7500 miles, but I will be checking its condition occasionally between now and then...especially once I get to 5000+ miles. It appears clear on the dipstick, but on a paper towel it looks faintly yellow-brown. The dino-oil looked dark on the dipstick and almost black on a paper towel. This change was at 5500 miles.

Not sure how valid a visual inspection is, but I definitely DON'T plan to run 10,000-15,000 miles like other posters claim to go.

 

0W-30 has the same hot viscosity as 5W-30. The difference is on the cold end where it has slightly lower viscosity. It meets all of the standards of 5W-30 but theoretically may improve FE by causing less drag when cold. I use it because it is the same price for Mobil 1 0W-30 and 5W-30. I haven't seen any difference in FE.

 

Ok cool thanks.

 

I run 5-30, but I run what is labeled as a "full synthetic". From what I've read on PriusChat, US standards don't insure that a 5-30 is a full synthetic, rather they insure any oil that passes certain tests gets to use the "full synthetic" label. To pass these tests requires at least a blend of high grade dino and full synthetic.

I run the full synthetic as cheap insurance against wear since I plan to keep my car until the wheels fall off. I extend the oil change interval just a little, to 6 or 7 thousand miles. I've noticed the oil stays much lighter in color between changes that it did with regular or high mileage oil. Since my engine is still clean inside, the synthetic must still be doing it's cleaning job. Maybe it stays lighter in color because it's more heat oxidation resistant.

I run Carquest full synthetic. It's a very good price here in Oregon. It says it's made by Ashland on the bottle, which is the company that makes Valvoline. Anyone else tried this oil? Can anyone verify that it is Valvoline in a different bottle?

Thanks, Dan

 

I always run Mobil One in all my cars. I've always used 10-30 in my 07 and decided to try Mobil One 0-20. No gain in mpg's and I noticed a little more valvetrain noise with the 20 in there. I went back to 10-30. I don't need real thin oil on start up as its never cooler than 70 degree's here.
Put your car in test mode once in a while and listen to the motor
and you will become familiar with all its sounds. Helpful if you think you have a motor noise issue.

 

A little basic oil info.
If the weight spec. has a "W" in the middle, as in 5W30, it means the two numbers are referenced to the freezing and boiling point of water.
So 5W30 oil has the equivalent viscosity of straight 5 weight oil at 0C or 32F and the equivalent viscosity of straight 30 weight oil at 100C or 212F. Oil temps in an engine vary from ambient (at startup) to about 300F, for the Prius.

If the oil doesn't have the "W" then all bets are off. The oil company can use just about any temp. they want.

Viscosity is basically how "thick" the oil is, or how fast it pours or runs. It's measured by pouring it through a restriction and timing how fast a specific amount flows through under gravity. There -are- more accurate ways of measuring viscosity, of course, but that is the most common.

For those living in the northern areas, a good lesson for you is to take a quart of oil and try pouring it at room temp. Then pour it back into the container, and leave it "outside", (or put it in the freezer - most freezers get down to about 0F or -18C). Try pouring it when it's that cold.
You'll be more gentle on your car on cold mornings when you see how thick the oil gets! Luckily, it only takes a few minutes for the oil to warm up enough to flow well.

 

Last service Toyota marked putting in 3.8 qts of 5W-30. I can't stand and watch them do it, so have to trust it.

Pre-paid maintenance for 3 years, so they do the work.

 

3.8 quarts is almost always too much. Let the car sit OFF for 10 minutes and check the dipstick yourself before leaving.

Why did you buy pre-paid maintenance?

 

Mobil 1 0W-30, 5W-30, and 10W-30 will test out a bit differently at the SAE J300 limit, at least according to current data:

Mobil 1 0W-30: 11.0 centiStokes at +100 C
Mobil 1 5W-30: 11.3 centiStokes at +100 C
Mobil 1 10W-30: 10.0 centiStokes at +100 C

Note: the 10W-30 is the older formulation. There was a 3-4 year period when Mobil thinned out their oils to improve fuel economy. The SAE J300 spec considers an oil to meet xW-30 specs if it tests out 9.3-12.5 centiStokes at +100 C

Under normal operating conditions in temps > -18 C, there should be little to no difference in fuel economy. Or, the difference will be so slight the average person won't even notice

No. It does NOT mean that at all

The SAE determines how oil viscosity is determined, by use of both dynamic and static tests. Such as a rotary viscometer with 1/10 degree C temperature control, and reference oils that are maintained by the ASTM

A "W" means that the oil being tested may NOT exceed a viscosity of 60,000 centiPoise, or 600 Poise, at the test temperature. A 0W-xx oil may not exceed this viscosity at the test temp of -40 C

A 5W-xx oil may not exceed this viscosity at -35 C. A 10W may not exceed the 600 Poise viscosity at -30 C. This tests relate to pumping at cold tests, used to determine yield stress at the oil pump inlet, and are referenced by ASTM D-4684

ASTM D4684 -08 Standard Test Method for Determination of Yield Stress and Apparent...

Cranking tests and measurements are different, they are referenced by ASTM D-5293.

ASTM D5293 -08e1 Standard Test Method for Apparent Viscosity of Engine Oils Between -5 and...

The catch is that the cranking tests are performed at test temperatures 5 C warmer than the pumping tests, by viscosity grade. Eg, an oil that passes the pumping test at -40, must also pass the related cranking test at -35 C. A failure in either test is an outright failure of the oil

The other end of the scale is also compared to reference oils. Oils must meet this test at the test temp of +100 C, except the HTHS test is performed at +150 C. This is a kinematic test, and is referenced by SAE J300 and ASTM D445

ASTM D445 -09 Standard Test Method for Kinematic Viscosity of Transparent and Opaque...

SAE 20: 5.6-9.3 centiStokes at +100 C
SAE 30: 9.3-12.5 centiStokes at +100 C
SAE 40: 12.5-16.3 centiStokes at +100 C

What all this means is that for most people, in a moderate climate, most oils will work about the same, in the average motor. In extreme climates, such as extreme heat, some oils will shear down and possibly cause long-term wear, in addition to forming deposits

At extremely low temps, the quality of an oil is much more apparent. Based on the SAE table, a 5W-xx oil only has to be "good" to -35 C. It is allowed to test "borderline" at -30 C. If your winter temps are that low, or lower, you should consider a 0W-xx oil

Here are some interesting test results provided by Mobil on their three 0W-xx oils, at -40 C

0W-20: 5,642 centiPoise
0W-30: 11,100 centiPoise
0W-40: 26,242 centiPoise

Note that all three oils easily pass, performing far better than the test maximum of 60,000 centiPoise at -40. They also perform far better than conventional 5W-30 oils, which usually turn solid at -40

However, there will be noticeble differences in starting ease at -40, if one uses the 0W-20