Question on oil weight?

According to the specs, Mobil 1 10W-30 should be fine in temps of +5 F to +30 F. There might be a teeny difference in fuel economy, compared to say Mobil 1 0W-30

I would leave it in. No sense wasting good clean oil. If you were talking about a conventional 10W-30, however, that would be pushing the cold temp limits of the oil

 

I suggest that you leave the existing oil installed for now. However if you have engine start problems (DTC P3191) then at that point you should drain the old oil and replace with 5W-30. If you have unused bottles of 10W-30, save them for summer use.

 

DTC P3191 Engine Does Not Start

This is a diagnostic code produced by the engine ECU if the engine refuses to start after a suitable period of time has elapsed. In that instance, the check engine light (amber colored engine light) will come on and the master warning light (red triangle) may also come on.

See attached TSB EG050-04 for details.

 

Yes, it does. Change the oil. A conventional 10W-30 will be borderline by 0 F and should never be used below -15 F. Once the temps get below +15 F, you could experience fairly noticeable fuel economy loss

 

The heavier weight oil may make the engine rough when it starts and stops. It will still lubricate just fine.

Being in "real winter" country, like Jay, I use Mobil 1. I'm currently using 5W30 year round. The car is fine with that. But as I said above, when cold, the engine is a little rough when starting or stopping. Once the engine gets a little warm engine starting and stopping is almost unnoticeable.

Once upon a time, we used 10W30 "standard oil" in the winter with no real problems. The -main- reason 5W30 is called for in most modern cars is because it improves fuel economy a bit, giving the manufacturers certain bragging rights, along with better government ratings.

 

I live in Ohio as well, I still would leave it in, no sense wasting it. And even though it gets cold here its not like its an arctic tundra. The 10w30 is thicker, but I would be shocked to hear of any problems. In fact when I have had older vehicles I would use a 10w40 to slow down a few gasket leaks, even in the winter I had never had any issues in my 16 years of driving. Also don't forget that 10W30 oil is still the top selling viscosity in the USA and at least half of all the quick change oil places put it in regardless of what comes in unless you specifically specify otherwise.

 

Don't overlook the basics of what each number means. The 10W (W=Winter) refers to the "startup" viscosity of the oil. The lower the number, the quicker a cold engine is lubricated. The 30 refers to the viscosity when at engine operating temperature. What you have is a poorer performing oil for cold startups. Since only you know how many startups per day and how cold, the decision could be based on your knowledge and desires rather than a group vote.

 

By this he means the actual error code that the computer could trigger, the error codes can be read via a compatible code reader.

As far as your synthetic question most synthetic oils are mixable with conventional (dino) oil. If you were going to switch to a synthetic because you were wanting the benefits of having an extended oil change interval it would be best to follow the the maintenance schedule for at least the first oil change after the switch. For example say at
55,000 miles you have only used dino oil and decide from here on out you want to use synthetic, Switch to synthetic at 55,000 then at 60,000 miles change the oil again as part of the 60,000 mile maintenance then from that point on feel free to take advantage of the longer intervals. Otherwise if you just go by the normal maintenance schedule no need to change early.

 

There are many different brand/weight oils, and their 5w & 10w viscosities overlap quite a bit. By that I mean there are 5w-30s that have are more viscous at room temp than some 10w-30s. Likewise, there are 10w-30s that are less viscous than 5w-30s at high temp.

ICEs are highly adaptable to a variety of oil weights. They are not delicate, lightweight, and easliy killed by using an oil that is slightly out of the recommended range.

It wouldn't hurt to start your car at 0* and even lower with that weight oil. The oil won't be solid, and it will flow. There are better for that temp, but your engine won't die.

Your 10w oil is no problem. Change it out at the next normal interval and you will have done no wrong. Be at ease.

As for the synthetic question, I don't buy synthetic an more. Regular, name brand oil has come a long way. 5,000 mile change intervals are fine for me. Multiple oil analysis' over multiple vehicles has shown highly adequate service using regular oil.

 

Typical Properties

Mobil 1 10W-30
Pour Point, ºC -45

Typical Properties
Mobil 1 5W-30
Pour Point, ºC -48

There doesn't appear to be very much difference in the low-temp pour point.

The Mobil Clean 5000 oils are not a lot different, but not being synthetic their cold pour points are higher. 5w-30 is ºC -33 and 10w-30 is ºC -36. Note the 10w-30 pours at the lower temp.

To also note, M1 5w-30 has viscosities of 64.8 at 40ºC and 11.3 at 100ºC. For comparison, the lightest 5w-30 I have found is Havoline Deposit Shield. DS has viscosities of 59.4 and 9.7, respectively. I haven't been able to find the cold pour point, but I would think it to be at least as good as Mobil Clean 5000.

M1 is a good oil. But it isn't the only oil.

 

As usual there are a lot of misconceptions on oil and the numbers on the top of the container (I was going to say can, but I haven't seen oil in cans for a few years now).

First, there is no problem mixing current (modern) synthetics with "normal" oil. You can even buy it mixed (it's called "synthetic blend"). Oh, and if he thinks one oil change is going to remove all traces of the "normal" oil I've got news for him. Most cars hold at least a litre in the engine/oil cooler, even if you change the filter. It would take a lot of changes to get most of it out. The Prius does so as well. So don't bother trying to "clean it out" with changes.

Second, if you see 10-30 on the container, that means at some unspecified temp the oil behaves like 10 weight oil and at some higher and still unspecified temp it behaves like 30 weight oil.
If you see 10W30 (even if they include a -) the oil behaves like 10 weight oil at 0C or 32F and it behaves like 30 weight oil at 100C or 212F. The "W" doesn't stand for "winter", it stands for water, as in freezing point and boiling point. A standards thing.

 

I have a question for our more knowledgeable members. If you do change over to a fully synthetic oil, how does that affect the extended warranty? I mean as far as needing to comply with the recommended service intervals (5000mi on the oil changes) instead of using the extended service interval? We changed to Mobil1 in our Jeep Commander and squeezed out an extra 3-4 mpg, I expect it would respond similarly with the Prius?

 

Every reference I have seen states the W is for Winter. (Wikipedia for an quick example)

 

Blueberry, if I understand what you are asking...

In general, using synthetic oil and extending oil changes past 5k miles (to, say, 8-10k miles) would only be a problem if,

1) you have an engine failure or condition that was specifically caused by synthetic oil or oil changes extended past the mfg's recommended intervals. Not checking your oil and running low does not count, as it is operator error. Sludge buildup and its effects may be a problem with normal oils but is not really a problem with a real synthetic oil. Mechanical failures are not likely to be caused by a flowing oil of proper amount, so would probably not really count as an oil related failure. Personally, I don't see how this could take place with the appropriate amount of a name brand oil.

or 2) You have a service manager trying to pawn other failure types off as "CLEARLY oil related" since you didn't follow the proper OCI. Be aware and be on guard for this.

Whether a true synthetic would give a Prius more MPGs, I wouldn't know. You would have to say, "Compared to which oil?" I did 10k miles on M1 (when it really was a true synthetic oil) and 10k miles on Quaker State. Both 5w-30 oils. Both under all conditions. There wasn't enough difference to say there WAS a difference. This was in the truck's V10, where the extra mechanicals should have shown a difference had there been one.

YMMV...

 

Yes, from I've been able to gather, the original W test was at 0°F (-18°C), not 0°C. Current tests are done at lower temperatures.

 

I'm away on business, so will have to make this quick

Everybody chiming in with different interpretations about "W" is flat out wrong. Period

The SAE J300 is used to determine an oil viscosity, both at operating temp, and in cold temp

Cold temp oils - the "W" oils - must meet an absolute viscosity limit of 60,000 centiPoise. No exceptions. This test is performed using a mini rotary viscometer, and is covered in detail by ASTM D4684. The test apparatus allows very precise temperature control of the sample oil, down to -40 C

The J300 table requires any oil rated "10W" to have an absolute maximum viscosity of 60,000 cP at -30 C. Any oil rated "5W" must not exceed 600 P - 60,000 cP - at -35 C. Any oil rated "0W" must not exceed 600 P at -40 C

Clearly, oils do not perform exactly the same. For example, Mobil 1 0W-30 is rated 11,100 cP at -40, which is far better than having an oil that hits 60,000 cP at the same temp

At operating temp, a kinematic viscosity measurement is used. The oil is rated in centiStokes, or cSt. The ASTM D445 offers precise details on what this test entails. There is also a high temp, high shear test associated, this is a dynamic measurement in milli Pascals per second, or mPa-s, performed at 10 ^ 6 shears per second, and an elevated test temp of +150 C

Briefly, any oil rated "30" (30, 10W-30, 5W-30, and 0W-30), *must* test out with a range of 9.3-12.5 cSt at +100 C. The HTHS must be a minimum 2.9 mPa-s

Any oil rated "20" (20, 5W-20, 0W-20) *must* test out with a range of 5.6-9.3 cSt at +100 C. The HTHS must be a minimum 2.6 mPa-s

To further confuse the issue, there is also a "borderline pumping temperature." Especially conventional oils, tend to hit this curve about 10 C before their absolute test rating. Eg. a 5W-30 must be "good" at -35 C, but tends to hit the borderline limit at -25 C. A 10W-30 must be "good" at -30 C, but tends to hit the borderline limit at -20 C

Another thing to keep in mind is the cranking viscosity, which is performed with a mini rotary viscometer. This is referenced in ASTM D5293 as the Cold Cranking Simulator - CCS - and is measured in centiPoise

Any oil rated "10W" cannot exceed 7,000 cP at -25 C. Any oil rated "5W" cannot exceed 6,600 cP at -30 C. Any oil rated "0W" cannot exceed 6,200 cP at -35 C. Anybody notice anything interesting about the MRV vs CCS temp scales?

The CCS is performed at temps 5 C warmer than the MRV test. The hope is that the engine simply won't crank when using too heavy an oil, this will prevent cavitation of the oil pump, and engine failure. If you have a warm battery, a booster battery, or the large M/G and NiMH providing starting current, there is the potential the engine could crank and start with no oil flow