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LIving in Texas we have had 20+ days over 100F this summer. I am changing to 10W40 Castrol Syntech... I feel it will handle the heat better than the European 0W40.. Has anyone else changed from Mobil 1 0W40??? Your thoughts.
Thanks
 

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You should be okay in Texas, cold starts should be rare for you, but there probably won't be a diffrence. I'd stick to 0W-40
 

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My '08 smart never had Mobil 1 0W-40. It did go 65 miles on the Mitsu engine factory's unknown fossil oil, then a 5W-30 ever since. My smart center in SE VA uses Castrol Syntec 5W-30. The 40-weight will do you more good in Texas than the 0W-.

Check your OpMan for smart's recommendtions on choosing the proper oil viscosity (it is in the new '09 manual).
 

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Simply stated...
The first number is a tested viscosity rating at cold temps. The thinner the oil is for starting a cold engine the better - and that is regardless of ambient temperatures. A 0W-40 oil is a much better alternative than a 10W-40 oil.

The second number is the tested viscosity rating at operating temps (ignoring the precise testing parameters). It is the significant number for your ambient temperatures and engine operating parameters.

All other considerations aside - the OW-40 oil is a superior blend to the 10W-40 oil. It is a mistake to think you are better off with the 10W-40 blend - you are most definitely not better off with that oil!

For generally knowledgable and reliable information on oils and related technologies go to bobistheoilguy forums.
 

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FWIW...

The first number (the "5" in 5w30) is only a relative number which basically indicates how easily it will
allow an engine to "turn over" at low temperatures. It is NOT a viscosity reference. In other words, a
10w30 is NOT a 10 weight oil in cold temperatures and a 30 weight oil in warm temperatures.
In fact, since SAE viscosity classifications only apply to an oil at 100 degrees C, it doesn't even make
sense to label it as a certain SAE viscosity at any temperature other than 100 degrees C.
Besides, if you thought about it for a second, it wouldn't make sense for a 10w30 oil to be a 10 weight
oil in the cold and a 30 weight oil in warm temperatures. What liquid do you know of that gets "thicker"
as its temperature increases or "thinner" as the temperature decreases?
I would venture to say you probably can't come up with one. This holds true for motor oil as well. If a
10w30 was a 30 weight oil at 100 degrees C and a 10 weight oil at cold temperatures, that would mean
it "thinned out" as the temperature dropped. That just doesn't make any sense considering what we
know about liquids. It just doesn't happen like that.
The fact is that a 5w30 motor oil is thicker in cold temperatures than in warm temperatures. However,
a 5w30 motor oil will be thinner than a 10w30 motor oil when subjected to the same low temperature
conditions - because the "W" number is lower. This is an indication of better cold weather performance.
In other words, a 5w30 flows better in cold weather than a 10w30 motor oil will. Think of the "W" as a
"winter" classification instead of a "weight" classification.
 

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FWIW...

The first number (the "5" in 5w30) is only a relative number which basically indicates how easily it will
allow an engine to "turn over" at low temperatures. It is NOT a viscosity reference. In other words, a
10w30 is NOT a 10 weight oil in cold temperatures and a 30 weight oil in warm temperatures.
In fact, since SAE viscosity classifications only apply to an oil at 100 degrees C, it doesn't even make
sense to label it as a certain SAE viscosity at any temperature other than 100 degrees C.
Besides, if you thought about it for a second, it wouldn't make sense for a 10w30 oil to be a 10 weight
oil in the cold and a 30 weight oil in warm temperatures. What liquid do you know of that gets "thicker"
as its temperature increases or "thinner" as the temperature decreases?

You really need to do a little more research on oil technology and how oils are rated and by whom.

Multigrade oils are tested and certified to have a specific rating at two different temperatures - -18 centigrade for it's cold rating, and 100 degrees centigrade for it's hot rating.
The designation 5W-30 means that the oil was tested to flow as a 5 weight single grade oil at -18 degrees C. The "W" does stand for "Winter". It does not stand for weight.
That same multigrade was also certified to flow as a 30 weight single grade oil at the hot temperature. This does not mean that it is thicker when hot than it was when cold. It isn't. All oils thin as they are heated and that includes multigrade oils. A Viscosity Index Improver is added to standard base oils to prevent them from thinning as much as they would otherwise. This allows them to behave as a thin oil at cold temps and as a thicker oil would when heated to a higher temperature.
Synthetic oils behave a little differently and don't require VI improvers.

That's the simple explanation. I can't be bothered to go into any more detail here now - for something a little more technical see http://www.carbibles.com/viscosity.html
Here's another one - http://mysite.verizon.net/oldhokie/windyridge/oil.pdf

You might also want to investigate rating systems and specifications for different oils to see how they compare.

Also, if you still doubt what I've said then why not try posting what you did here at the bobistheoilguy forums and see how they respond? Those forums are populated by many tribologists and other petroleum experts and interested individuals. http://www.bobistheoilguy.com/
Here's a little bit of general information from that site. http://www.bobistheoilguy.com/oildefinitions.html
 

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You really need to do a little more research on oil technology and how oils are rated and by whom.
Not to sound rude, but you should also do some reading on your own before criticising other peoples' information. Your statements on viscosity are not accurate and several of your comments contradict themselves.

Take a look at the file that lebikerboy posted and you'll find all of the (correct) information you need.
 

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You should be okay in Texas, cold starts should be rare for you, but there probably won't be a diffrence. I'd stick to 0W-40

I agree....I'm here in Indiana and while we have our fair share of 90+ temps, we also have temps in the minus' too. With the oil being changed every 10K, you're going to be constantly going from one extreme to another during the course of one change.

Texas? You should be good with the 10w40, but anywhere your temps get below 30 degrees on a regular basis during the winter....stick with the 0w40. :)
 

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We get temperatures here in Kelowna ,British Columbia, Canada (at the northernmost end of the Great Sonoran Desert) from over 100F in summer to below -30F in winter. I always use 0W40 in my smart car, with no issues in any season.

Cheers.
 

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posted before...doing it again...
Introduction to Motor Oil

jetfuel
I'm familiar with Dr Haas and his writings about oil. He should be read carefully.

lebikerboy - I have no idea what you are referring to. I am also quite familiar with that publication you referenced. It in no way contradicts anything I've said. If you believe it does then make a direct reference and quote which could be discussed.
You may not have reviewed the references I presented in the other post. One of them is actually from the author of that Oil Bible publication.

Padawan - also, please discuss what you believe was inaccurate in my description of multigrade oils and viscosity as well as pointing out how my words were contradictory. Perhaps you didn't fully understand what was written. It is not possible to arrive at understandings when vague comments are being made.

As I alluded to before, the way oils are rated is being misunderstood. There is another misunderstanding of what viscosity is suitable. Further, oil technology has been changing quite rapidly for some time now. The attitudes toward what is suitable, the frequency of oil changes, and the differences in types of oil really need to be researched and understood better.
I've been involved with oil discussions on a sports car forum for many years now. There, the general understandings have been improving and discussions like this seldom take place any more.

Lets really clarify what is being talked about. It will be helpful for all concerned.
 

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In your post, you state:

"Multigrade oils are tested and certified to have a specific rating at two different temperatures - -18 centigrade for it's cold rating, and 100 degrees centigrade for it's hot rating. The designation 5W-30 means that the oil was tested to flow as a 5 weight single grade oil at -18 degrees C."

In actuality (quoted from the article):

"The first number (the "5" in 5w30) is only a relative number which basically indicates how easily it will allow an engine to "turn over" at low temperatures. It is NOT a viscosity reference. In other words, a 10w30 is NOT a 10 weight oil in cold temperatures and a 30 weight oil in warm temperatures. In fact, since SAE viscosity classifications only apply to an oil at 100 degrees C, it doesn't even make sense to label it as a certain SAE viscosity at any temperature other than 100 degrees C."

Each W grade must meet certain "startability" requirements at a specified temperature. For instance, a 0W grade oil must have a maximum CCS centipoise (cP) value of 3250 @ -30 degrees C as well as a maximum MRV cP of 60,000 @ -40 degrees C. A 5W grade oil must have a maximum CCS cP value of 3500 @ -25 degree C and a maximum MRV cP of 60,000 @ -30 degrees C. The lower the cP value for both specifications, the better."

The "W" rating is not simply a measure of the oil's "weight" at -18 degrees. As stated earlier, it is a relative indicator of how well the oil will flow at low temperatures.

You also state several times that a 0W-40 is superior to a 10W-40, and that "the thinner the oil is for starting a cold engine the better", both of which are absolute statements that are not necessarily accurate.

Myself and others may have misinterpreted what you wrote, so perhaps there is indeed need for further clarification in the thread.

And since we're being specific, "its" is the possessive adjective meaning "belonging to a thing", while "it's" is the contraction of "it is."
 

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Padawan, thanks for clarifying what you are referring to. The information you quoted is incorrect or taken out of context, however. Where is it from?

Multigrade motor oils are indeed tested according to SAE at two temperatures, at -18 and at +100 degrees centigrade.
Since the Engine Oil Bible has been referenced - the author actually stated; "...the winter grades of 5W, 10W and 20W are determined by the oils' viscosity at 0° Fahrenheit (-18°C), while grades 20,30, 40 and 50 are determined by its viscosity at 212° Fahrenheit (100°C). Those are the predetermined temperatures."
The first number in an SAE multigrade rating was tested to have that viscosity (flow) rating at a cold temperature. It flows at that temperature as a single grade 5 wt oil would flow at the same temperature. Since it is a cold rating of the multigrade oil, the engineers who chose to use "W" to indicate that it is a cold rating must have had something in mind that the letter "W" should represent. I understand that there is some controversy regarding whether it stands for anything at all, but since it is a cold rating then it's generally considered that the word "winter" could be the origin of the letter "W". But, it certainly does not stand for the word "weight".
You might also consider that a multigrade petroleum motor oil has as a base oil the weight of its cold rating. Viscosity Improvers are added that cause it to not thin out any more than a single wt oil of the hot rating at a measured hot temperature of 100 C. Synthetic oils behave much differently and do not require viscosity improvers. These base oils are chosen to act similarly to the hot rated single wt oils but they do not thicken as much as petroleum oils as they cool. They don't have waxes that thicken when cooled as petroleum oils do so they naturally flow better when cold.

Also, the thinner an oil is the quicker it will flow and lubricate bearings and valve train during a cold start. The requirement for good flow when cold is the primary reason why synthetic oils were first produced. Flow is the critical consideration.

Dr Haas is a proponent for using thin viscosity oils that flow well when cold. Although the reference provided from his writing is old information now, it nontheless is accurately informative.
Here is another reference for Dr AE HAAS - http://www.bobistheoilguy.com/aehaas/index.html
He states; "Remember that most engine wear occurs at startup when the oil is too thick to lubricate properly. It cannot flow and therefore cannot lubricate. Most of the thick oil at startup actually goes through the bypass valve back to the engine oil sump and not into your engine oil ways. This is especially true when you really step on that gas pedal. You really need more lubrication and you actually get less."
Also - "
I truly believe that oil is much better being too thin than too thick. Over the years we have been going to thinner and thinner oils despite hotter engines with turbos and the like. The tendency is that people figure they need a 40 weight oils but then use a 50 instead. Better thinking is that if you think you need a 40, use a 30 weight oil instead. I firmly believe this based on all I know about oils."
And - "Remember, the only difference between a 0W-40 and a 10W-40 is that the 0W-40 thickens less after you turn off your engine. It is still too thick in the morning at startup but not as thick as the 10W-40." The significance of this statement is that even a "0" wt oil is too thick for cold startup. The word 'cold' by the way does not refer to ambient temperature but rather to an engine and oil that is not at hot working temperature.
He also stated; - "Everybody including good mechanics think they are experts in this field but few understand engine oils. Most of what I hear is the opposite of the truth. It is however easy to see how people get mixed up as there is always some truth to the misconception."

To confuse matters further - the "0" W oils, by the way, do not all have the same viscosity when cold. The reason for that is due to a discrepency in the way the rating system works. When first designed the system did not account for oils of that cold vis wt. A 0W-20 and a 0W-40 synthetic oil could vary by as much as 20 cST when cold even though they are both designated as "0" weight. Nontheless, they are both thinner (flow easier) when cold than a 5W oil would be.

Here is another reference that might clarify some things. http://deniliquinsportingcarclub.com/index.php?option=com_content&view=article&id=37:eek:il&catid=31:eek:il&Itemid=9

And another.
http://www.autospeed.com.au/cms/A_0788/article.html

As to the differences between Mobil's 0W-40 and the 10W-40 - a research on oil forums can provide information there. Not all multigrades are the same, whether that be petroleum or synthetic. There are differences in base oils and additive packages. Some also retain their original qualities longer than others. They are also formulated to satisfy different standards.
 

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Padawan, thanks for clarifying what you are referring to. The information you quoted is incorrect or taken out of context, however. Where is it from?
The information came directly from this document: http://www.zag.si/~jank/public/bmw/oil_bible.pdf

It is not incorrect or out of context. If you can find where that article states "W" testing is conducted at -18 C or that a 5W oil performs like a fixed 5 weight when cold, please direct us to it.

Your statements by Dr. Haas are, by your own admission, old. And I have yet to see any test data done with super-thin oils (sub-0W) in start-up situations that demonstrates they provide better wear protection under those conditions. In the absence of that data, I won't discount his argument, but hard evidence would far more convincing that one man's "firm belief."

Finally, you compare M1 10W-40 to 0W-40 as proof of your argument that 0W-40 is the better viscosity. My point, however, was that stating in absolutes that a 0W-40 is ALWAYS better or more preferable than a 10W-40 is not correct.
 

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So, to take a short detour, I can see the benefit of the "0W" part of the spec here in Ohio where we get sub-zero temps in the winter. However, not sure about the "40" part of things. Seems like pretty thick oil to be pushing with a tiny engine, no matter how high the ambient temps are. Wouldn't 0W30 oil work just as well and provide a little extra gas mileage due to lower viscosity on the upper end? :)

https://www.mobiloil.com/USA-English/MotorOil/Oils/Mobil_1_0W-30.aspx
 

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In short, yes. I've actually been toying with the idea of running a good 0W-20 or 5W-20 after seeing a number of very positive UOA (used oil analysis) results from various different engines.
 

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While out on the short detour, if one wants a little better gas mileage look for an oil that is ILSAC GF-4 certified (+/- 2% savings). No 40-weight qualifies as a GF-4.
 
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