why do we have many oil grades when we can just go with 5w/50?

[StiMan]

hi As u may know Mobile 1 has 5w/50 synthetic. Why is therefore a need for other oils that fall within this range e.g 10/40 , 10/30, 15/50 basically anything 5 to 50 viscoscity would all be covered by 5w/50. can someone give me an explaination as to why 10/40 or 10/30 would be chosen over 5/50? i'm sure there is a scientific reason, but logically i cant see how. cheers

 

[Slade]

Hey there, Well, to tell the truth even though the oil is RATED for those weights being the fact that it has a warm weight of 50 it will tend to be thicker. Yes, it will run at the 5w during colder weather but, oils like that tend to be a little thicker during COLD winters. In ND I run 5w30 because it's thinner overall for winter running conditions. Unfortunately, I DO NOT believe in the ONE SIZE FITS ALL philosophy when it comes to oil. Slade

 

[Last_Z]

There is also the issue of shear.....such a wide spread means more viscosity improver....this will shear over time and can even form deposits. Also, a 50W might be too thick for some engines and cost HP and gas mileage. Rick

 

[RavenTai]

I am no where close to an oil expert either but I do know that not everybody needs a 50wt oil at operating temperature, the extra thickness is not needed by all engines and would be a waste of gas for most also to get a 5wt oil to act like 50wt at temperature requires a lot of Viscosity index improver's, VII's are one of the first additives to degrade in oil leaving you with much less than 50wt at temperature, also VII's can “temporary shear” in bearings, the oil pump had to pump thick oil to the bearing and then when it got there it sheared down and did not protect as well, worst of both worlds synthetic may not need as much VII's to get that spread but AFAIK no oil synthetic or no would be able to make 5-50 without VII's some people look for a least spread they can find that will still work for their conditions *EDIT* I gues I am the slowest typer [ November 15, 2003, 02:08 AM: Message edited by: RavenTai ]

 

[pscholte]

Won't it be interesting when the first analysis comes out showing a synthetic "straight weight" is the best oil one can use!

 

[Shannow]

pscholte, In my search for what to run in my turbodiesel, one oil that really took my fancy, and the mobil tech agreed it would be good, but was unavailable down under was DelvacHP30. Delvac HP30 viscoscity index 122 pour point -30c

 

[pscholte]

quote:

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Originally posted by Shannow: pscholte, In my search for what to run in my turbodiesel, one oil that really took my fancy, and the mobil tech agreed it would be good, but was unavailable down under was DelvacHP30. Delvac HP30 viscoscity index 122 pour point -30c

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Shannow, What kind of annual temperature variation do you see? I'm thinking that a synthetic "monograde" does not behave like a dino mono and would be able to handle a wider range of temperatures.

 

[TC]

Expanding on others' comments with some articles I've kept, multi-viscocity oils are created by adding polymers to a light base (5w, 10w, 20w), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers unwind into long chains that prevent the oil from thinning as it normally would. Always use a multi grade with the narrowest span of viscosity that is appropriate for the temperatures you will encounter. In winter base your decision on the lowest temperatures you will encounter, and in summer on the highest temps you'll encounter. Polymers can shear and burn, forming deposits that can cause ring sticking and other problems. Ther greater the spread (such as with 5w-50), the more polymers that are required, and fewer polymers are better for all engines. The wide viscosity range oils, in general, are more prone to viscosity and thermal breakdown due to higher polymer content. It is the oil that lubricates, not the additives (except for anti-wear and anti-friction compounds such as zinc and moly). Oils that can do their job with the fewest additives are best. [ November 15, 2003, 07:10 PM: Message edited by: TC ]

 

[Shannow]

quote:

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Originally posted by pscholte:

quote:

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Originally posted by Shannow: pscholte, In my search for what to run in my turbodiesel, one oil that really took my fancy, and the mobil tech agreed it would be good, but was unavailable down under was DelvacHP30. Delvac HP30 viscoscity index 122 pour point -30c

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Shannow, What kind of annual temperature variation do you see? I'm thinking that a synthetic "monograde" does not behave like a dino mono and would be able to handle a wider range of temperatures.

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pscholte, we are supposed to get down to -11C (12F), but the coldest I've seen here is -8C. Summer we get a few 40 plus 105F days per year. (The 25W-70 started in my Camira (J2000 wagon) in -7 this year) In this area, I think I'd happily take a synthetic straight 30 with no VI improvers.

 

[userfriendly]

I doubt if the HP 30 is a synthetic or group III, but quite likely a group II+. It would be interesting to know if the formula was bright stock free. In NA Mobil has 1330 and 1630 that show the same specs as your HP 30. By looking at the viscosity typicals one could assume that the HP30 would easly pass an SAE 15W cold cranking and flow test, qualifying that oil as a 15W30 (and the HP40 a 20W40). Petro Canada has a similar product called Duron 30, with a lower ash than the Mobil product more specifically targeted for DDs in cold weather. I think these and other modern single grade oils are a bargin and can be bought for around $2.00/litre. [ November 16, 2003, 08:08 PM: Message edited by: userfriendly ]

 

[Shannow]

userfriendly, can't answer much on the HD30, but I do agree that it's probably not a full synthetic, if it even goes that far. We get delvac 1330 down here, mineral, V.I of 95. delvac 1630 isn't on the books. I actually meets my nissan specs, but is ruled out in the middle of winter and middle of summer. I'd use the HD30 'though.

 

[Dr. T]

It's a great question... I think a 5-50 is an excellent grade for climates where temperature extremes are noted. eg. in Canada, it can range from -30C to +40C. This definately makes the 5-50 an all-season oil. However, due to the comments above, a 15-50 would be more suited for warmer climates such as Florida, Texas, etc. due to it's somewhat higher grade stability (due to a smaller viscosity range). Unfortunately, in N.A. we're all brainwashed into using a 30 weight oil (due to cheap disposable nature of our cars/economy)...so any comments re: a 50 weight will turn a lot of people off in the first place.