5W40 synthetic diesel engine oil in a modern gasoline engine?

[Leejohn]

If you are changing at the 100hr mark what is being gained for double the money?

 

[ray66v]

Recently in my V8 truck in non-severe service I went almost 10,000 mile on synthetic oil with a quality filter. I used to change with less mileage than this but a lot of guys that test their oil say it can go even longer than 10,000 miles. In tractors that get severe usage I change once a year and in those with lighter usage maybe 18 months. I don't usually hit the 100 hours between changes.

I change a tractor to synthetic at 100 hours or so and vehicles at maybe a few thousand miles. I think even this is changing because I have owned two vehicles that came from the factory with full synthetic.

Unless your engine is designed to use a specified breaking oil, (very few still do), there is no need to wait, to switch from mineral to synthetic oil.

Both types of oil are similar in lubricity today, at normal temperatures. So, it isn't going to break in any differently on either one.

 

[RalphVa]

If I could get 0w30 synthetic diesel rated, I'd use it in everything. As the market goes, I'm using 5w40 Mobil 1 or T6 5w40 diesel rated in everything except my Tacoma and Jetta TDI. I put 0w20 in the Tacoma to get more mpg. In the TDI, I put 5w30 Castrol special ESP stuff from the dealer because Mobil 1 ESP is not available locally and is much more expensive.

Ralph

 

[DarkBlack]

Your logic is flawed as are many others.

5w30 is NOT thinner than 10w30
5w40 is NOT thinner than 15w40

They are the SAME.

Last number (after the w) is the oil thickness. The first number tells you how much it thickens when cold. That is why you don't notice any additional leakage in the old tractors. Because you are running the SAME weight oil in there. Just a little better performing as it don't thicken up "as much" when cold as 15w40 does.

Me thinks you got it all bass ackwards.

 

[Copperhead]

Well, he does have it generally correct, just maybe not very clear on first reading. The first number is the "Winter Flow Rating". That is what the "w" stands for. It has nothing to do with weight. The number after the "w" is the weight of the oil at operating temperature. The lower the first number, the better the flow at colder temps. While cold flow may give the impression of being "thinner" a 5w40 and a 15w40 are the same thickness.... both 40w oils. Some confuse restricted flow with thickness. You have to look beyond the appearances and look at the molecular level.

I have not found any appreciable need for something like a 0wXX oil. I don't live in the interior of Alaska anymore. A 5wXX or 10wXX serves my needs quite well. The problem that can occur when the spreads between the cold flow rating and the weight of the oil increases, the amount of viscosity improvers also is needed. it is those VI's that tend to shear under pressure and the motor oil breaks down. a 10w30, for instance, is more shear stable generally than a 15w40. And especially more so than a 5w30 or 5w40. And the issue I have with a 0wXX oil is that the cold flow to viscosity ratio is so extreme, that shearing is something to seriously consider. There are different quality VI's that can negate, somewhat, the dramatic effect of shearing, but cannot eliminate it. Each individual application is different. Chevron recently brought out a 15w30 HDEO that is extremely shear stable. They are pushing it for local P&D type trucking operations primarily.

I have zeroed in on 10w30 as the best overall performing oil for all my diesels. From my little oil burner motor in my NH TC33DA all the way on up to my Detroit 12.7L in my semi truck. Year round in the upper midwest. And most of my gasoline engines also get a 10w30, though not necessarily the same oil as I am putting in the diesels.

 

[arrow]

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I have not found any appreciable need for something like a 0wXX oil. I don't live in the interior of Alaska anymore. A 5wXX or 10wXX serves my needs quite well. The problem that can occur when the spreads between the cold flow rating and the weight of the oil increases, the amount of viscosity improvers also is needed. it is those VI's that tend to shear under pressure and the motor oil breaks down. a 10w30, for instance, is more shear stable generally than a 15w40. And especially more so than a 5w30 or 5w40. And the issue I have with a 0wXX oil is that the cold flow to viscosity ratio is so extreme, that shearing is something to seriously consider. There are different quality VI's that can negate, somewhat, the dramatic effect of shearing, but cannot eliminate it. Each individual application is different. Chevron recently brought out a 15w30 HDEO that is extremely shear stable. They are pushing it for local P&D type trucking operations primarily.

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The primary reason for auto manufacturers to have moved to 0 weight is for engine efficiency. Just about every manufacturer is striving for that. Less friction means more gas mileage. I have an all wheel drive Forester that regularly gets 35 mpg. It uses 0-20 synthetic. Shear concerns have more to do with dino oil than synthetic which remains pretty stable.

 

[Wolfy]

I am not convinced that regular 5W30 is equal to regular 10W30 at all operating temperatures , but I am convinced that synthetic 5W30 is superior to both of them.

 

[Copperhead]

The primary reason for auto manufacturers to have moved to 0 weight is for engine efficiency. Just about every manufacturer is striving for that. Less friction means more gas mileage. I have an all wheel drive Forester that regularly gets 35 mpg. It uses 0-20 synthetic. Shear concerns have more to do with dino oil than synthetic which remains pretty stable.

The issue is not quite as you stated. What is the viscosity of a 0w20 weight oil... 8.5 - 8.7 cSt at 100C. What is the viscosity of a 5w20...8.5 to 8.7 cSt at 100C. It doesn't matter. At operating temperature, the viscosity is the same. As I have contended, the 0 or the 5 in front of the "w" is winter flow rating only. Nothing to do with viscosity. There is no 0 weight oil, synthetic or not, on the consumer retail market. There is a 0 winter flow rating, in the form of 0w20, 0w30, 0w40, but not a 0 weight.

There is an argument to be made that a 20w oil is more fuel efficient than a 30w oil, and that would be the reasoning for auto OEM's specifying a 20w as opposed to a 30w oil, but the winter flow rating has virtually no effect in that regard.

Wolfy may not believe that a 5w30 and a 10w30 are not the same at operating temperature, but that doesn't mean that they aren't. All of these oils have virtually the same viscosity at operating temperature. I selected different brands to prove the point in fairness....

A modern synthetic 5w30 has a viscosity of roughly 10.4 cSt at 100C (Amsoil)

A modern synthetic 10w30 has a viscosity of roughly 10.2 cSt at 100C (Mobil 1)

A modern conventional 10w30 has a viscosity of roughly 10.5 cSt at 100C (Pennzoil)

As I have stated, a oil of a particular weight have the same viscosity. How they flow when cold in the winter is another issue and the number in front of the "w" is that rating.

There is a case that a synthetic has better overall properties, for sure. But it still has the same viscosity in the same grade as a conventional. How an oil has the viscosity it does and and the winter flow rating it does is primarily dependent on additional viscosity modifiers that are present in the oil. Some, like synthetics, require very little VI to reach the goal. Conventional's generally need more VI to have a low cold flow rating. There is a limit to how much VI you can use in an oil to achieve this. This is why you cannot buy a conventional 0w30 for instance. It is not practical to make one. It requires a synthetic or at a minimum a synthetic blend.

 

[arrow]

The issue is not quite as you stated. What is the viscosity of a 0w20 weight oil... 8.5 - 8.7 cSt at 100C. What is the viscosity of a 5w20...8.5 to 8.7 cSt at 100C. It doesn't matter. At operating temperature, the viscosity is the same. As I have contended, the 0 or the 5 in front of the "w" is winter flow rating only. Nothing to do with viscosity. There is no 0 weight oil, synthetic or not, on the consumer retail market. There is a 0 winter flow rating, in the form of 0w20, 0w30, 0w40, but not a 0 weight.

There is an argument to be made that a 20w oil is more fuel efficient than a 30w oil, and that would be the reasoning for auto OEM's specifying a 20w as opposed to a 30w oil, but the winter flow rating has virtually no effect in that regard.

Wolfy may not believe that a 5w30 and a 10w30 are not the same at operating temperature, but that doesn't mean that they aren't. All of these oils have virtually the same viscosity at operating temperature. I selected different brands to prove the point in fairness....

A modern synthetic 5w30 has a viscosity of roughly 10.4 cSt at 100C (Amsoil)

A modern synthetic 10w30 has a viscosity of roughly 10.2 cSt at 100C (Mobil 1)

A modern conventional 10w30 has a viscosity of roughly 10.5 cSt at 100C (Pennzoil)

As I have stated, a oil of a particular weight have the same viscosity. How they flow when cold in the winter is another issue and the number in front of the "w" is that rating.

There is a case that a synthetic has better overall properties, for sure. But it still has the same viscosity in the same grade as a conventional. How an oil has the viscosity it does and and the winter flow rating it does is primarily dependent on additional viscosity modifiers that are present in the oil. Some, like synthetics, require very little VI to reach the goal. Conventional's generally need more VI to have a low cold flow rating. There is a limit to how much VI you can use in an oil to achieve this. This is why you cannot buy a conventional 0w30 for instance. It is not practical to make one. It requires a synthetic or at a minimum a synthetic blend.

You are correct. There is no 0 weight per se. My assertion was to describe nomenclature as stated on the product container for clarity (in this case 0w-20). As manufacturers move toward better engine efficiencies and tolerances become tighter, it becomes important to establish less frictional forces at start up along with less resistance for overall running. Sludge is a primary enemy for this type of build and synthetics do much to relinquish this concern.

 

[Copperhead]

The start up contention would be valid, getting oil thru the motor more quickly using a 0wXX vs a 5wXX. And that is primarily dependent on the outside ambient temperature. On a warm summer day, there is virtually no difference in initial flow at startup from a 0wXX oil and a 5wXX oil and a 10wXX oil. But on the less resistance for overall running, that is in the area of whether one has a 20w, 30w, or 40w. I am all for lower viscosity oils that are being recommended by OEM's. There are a number of benefits to doing so, with fuel economy only part of the reason. Hydrodynamic lubrication is a larger concern. All the heavy diesel OEM's are now fully on board with using 30w oils instead of the old 40w oils. And most all the auto/pickup folks have jumped on 20w oils for most of their engines. But I have not bitten into the idea that a 0 winter flow rating is all that critical unless one is in the winter in N. Dakota. Primarily because it takes more viscosity improvers to do a 0 winter flow rating than a 5 winter flow rating. And viscosity improvers are the main concern of oil viscosity break down.