What is the different between 15w - 40 and 10w-40 meant in the diesel engine oil?

Answer 1

Diesel don't need something as thin as 10wt. to start. 15 is plenty. I use 15-40 wt. in my gasoline trucks for years in the winter.

Answer 2

The Society of Automotive Engineers Viscosity Classification

The terms SAE 10W-30 and SAE 15W-40 are widely used.
Any viscosity grade should be proceeded by the initials SAE.
This stands for the Society of Automotive Engineers and indicated that the following viscosity classification refers to their definitions. It should be noted that SAE is not a performance category it only refers to the viscosity of the oil. When comparing oils the reader should not only compare the SAE viscosity grades of two oils but also the engine performance classifications in order to be able to fully compare
performance.

Let us consider the following: SAE 5W-40.

The fact that this classification has two parts; the 5W and the 40
indicates that the oil is a multigrade. The first number with the
suffix 'W' indicates the oil's performance at low temperature. In fact the 'W' stands for winter. The lower the 'W' number the lower the viscosity of the oil. Therefore an SAE 5W oil is a lower viscosity oil than an SAE 10W oil.

Since diesels are hard to start in winter, a 5W low viscosity number is appropriate.

The number after the W, in the above case '40'; gives a measure of the oil's viscosity at high temperature. Again the lower the number the thinner the oil is at high temperature. So an SAE 30 is a thinner, or less viscous, oil than an SAE 40.

A multigrade oils is an oil that has two parts such as SAE 5W-40, or 20W-50. A monograde oil only has one part, such as SAE 30, or SAE 40.

The choice of viscosity grade is a difficult subject. The
manufacturer's recommendations should be followed.

Answer 3

For the laymen , the oils are mixed (one for starting and one for running) think of it as density with higher numbers being the thicker / denser oil . They are a mix of different ones because the seasons have different temps (winter - 10 weight - to summer - 15 weight ) so you want a lighter oil in there during the winter for easier starting. The higher numbers are the density when running & since all engines run hot you want the thicker oils (40 weight) to maintain the lubrication of the moving parts once it is running.
I was probably confusing here , but that is my attempt at a laymans explanation.

Answer 4

Beyond the weight- you need to make sure you're using the right GRADE of oil for a diesel engine. I beleive it's a "CF" code on the seal on the back (someone correct me if I got the letters wrong) Most 10w40 oils are not the right formula! All 15w40's are because that's what the standard is. If you don't like the performance, swith to a synthetic or a blend :-)

Answer 5

The winter viscosity rating is lower (the 10W) in the 10W-40.
If you are in a cold climate use the 10W-40.

engine oil
Engine oil grades
As long ago as 1911 the Society of Automotive Engineers recognized a need for standardizing grades of oil for automobile engines. Today the ratings are provided in collaboration with the ASTM and the American Petroleum Institute (API).

In the United States, engine oil ratings are indicated by a trademarked circular design on the package. The mark contains three pieces of information. In the inner circle is a viscosity grade. In the upper part of the outer circle is an API Service Classification, and the bottom of the outer circle may contain an energy conservation rating.

The package may also have a starburst symbol. The presence of this symbol indicates that the oil meets standards set by the International Lubricant Standardization and Approval Committee, whose members represent American and Japanese automobile manufacturers.

Viscosity
The purpose of the viscosity rating is to assure that, in the climate in which the engine is operated, the oil will always be able to flow through the engine's lubrication system. Eleven grades are defined. Six of them end in the letter “W,” beginning with “0W” and proceeding in steps of 5 to “25W.” The W stands for winter. The remaining five grades go from “20” to “60” in steps of 10, without the W. In general, higher numbers mean higher viscosities.

The viscosity of the oil is tested at 100°C. Its viscosity must be greater than a minimum that is specified for each grade. For the grades without a W, a maximum viscosity is also specified. This test basically ensures the oil will perform in a warm, running engine.

For grades ending in W, in addition to the minimum viscosity at 100°C test, a low temperature test is required. The temperature depends on the grade; for the 0W grade it is 35°C , for example. The purpose of the low temperature test is to ensure that if the oil's viscosity is low enough to permit cranking, it will also be low enough to be pumped through the engine. (Those processes involve different kinds of viscosity, so the cranking viscosity is measured in centipoises and the pumpability viscosity in centistokes.) The test temperatures rise by 5°C for each grade; oils with the lower numbers are intended for climates with colder winters. However, to select a viscosity grade for a particular car, consult the owner's manual and not just an outdoor thermometer.

Multiviscosity oils, such as “20W–50,” must satisfy both the low temperature cranking and pumping test for the grade indicated first, and the 100°C test for the second grade. Such an oil would also pass the tests for all the grades in between.

Service classification
The original grades were based only on viscosity. In 1947, three service classifications were added:

Regular, which was straight mineral oil
Premium, which had added anti-oxidants
Heavy Duty, with anti-oxidants and detergents
Both engines and the technology of lubrication became increasingly more sophisticated, so these classifications were replaced in 1952 with:

ML, MM, and MS classifications, in order of increasing quality, for oil for gasoline engines
DG, DM, and DS, in order of increasing quality, for diesel engines
After a number of revisions, those classifications were replaced by an entirely new, more easily extended system in 1983.

For gasoline engines, service classifications start with SA and proceed through (so far) SJ. Classifications SA through SF are considered obsolete, except that SE and SF are needed for certain smog systems which can be poisoned by additives present in later classifications. SA has no requirements at all; while the others are for earlier generations of engine (SC, 1964; SD, 1968; SE, 1972; SF, 1980; SG, 1989; SH, ; SJ, 1996). SJ is suited to a 1996 engine.

A similar set of classifications covers diesel engines. CA, CB, and CC are obsolete; CD, CD-II, and CE are in current use.

Energy conservation
If present, the marking will be either “EnergyConserving” or “EnergyConserving II.” To qualify as “EnergyConserving,” an engine oil must improve fuel economy in laboratory tests by at least 1.5% when compared with a reference oil. If the improvement is 2.7% or more, the oil can be labeled “EnergyConserving II.” These ratings don't guarantee that switching to “EnergyConserving” oil will improve mileage by 1.5% in a particular car, because of the large number of other factors at work.

Answer 6

Not much in the way of viscosity..... (they do make a 5w-40 deisel oil) but never use a sf rated (spark fired) oil in a diesel... it can't handle soot.

Using cf (compression fired) oil in a gas engine is fine, just not the other way around.

Answer 7

motor cycle can I use 2040 diesel the bike is a Harley 2012