Can anyone tell me how a 15/40 diesel oil changes viscosity as it reaches the end of its duty cycle? Are some better than others? Do they get thicker or thinner? Thanks Roger
Changing Viscosity
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Hi,
Roger - in my experience the mineral HDEO's tend to get thicker as intended as long as fuel dilution has not intruded
Synthetic HDEO's tend to end up about 15% above their VOA
Depending on engine type and all other factors being equal of course. And depending on operating conditions too
Regards
Roger - in my experience the mineral HDEO's tend to get thicker as intended as long as fuel dilution has not intruded
Synthetic HDEO's tend to end up about 15% above their VOA
Depending on engine type and all other factors being equal of course. And depending on operating conditions too
Regards
Roger:
There are so many variables involved I would hesitate to guess. All I can give are some examples:
1. HD diesel motors really load the oil with soot, especially if they're the new motors with EGR. Soot will thicken the oil to a sludge if you have too long an OCI. Changing your primary and bypass filters at the recommended interval really helps here.
2. When HEUI (Hydraulic-actuated Electronic Unit Injection, uses oil pressure to make the injector work) first came out, a lot of the cheaper 15W-40 oils experienced permanent viscosity loss due to the extreme shearing caused by the injectors. In some cases the oil sheared right back to a SAE 15W basestock. Oils like Amsoil 15W-40 and Mobil Delvac 1 5W-40 didn't appear to have that problem. Neither did straight SAE 30 and SAE 40.
Also, is the basestock synthetic or regular? A good synthetic basestock such as Amsoil 15W-40 or Mobil Delvac 1 appears highly resistant to shear.
The Esso XD-3 15W-40 appears to be well formulated too, though Esso does warn that continued use past recommended OCI in high soot and high shear can degrade it.
Sorry if I couldn't be more specific.
Jerry
There are so many variables involved I would hesitate to guess. All I can give are some examples:
1. HD diesel motors really load the oil with soot, especially if they're the new motors with EGR. Soot will thicken the oil to a sludge if you have too long an OCI. Changing your primary and bypass filters at the recommended interval really helps here.
2. When HEUI (Hydraulic-actuated Electronic Unit Injection, uses oil pressure to make the injector work) first came out, a lot of the cheaper 15W-40 oils experienced permanent viscosity loss due to the extreme shearing caused by the injectors. In some cases the oil sheared right back to a SAE 15W basestock. Oils like Amsoil 15W-40 and Mobil Delvac 1 5W-40 didn't appear to have that problem. Neither did straight SAE 30 and SAE 40.
Also, is the basestock synthetic or regular? A good synthetic basestock such as Amsoil 15W-40 or Mobil Delvac 1 appears highly resistant to shear.
The Esso XD-3 15W-40 appears to be well formulated too, though Esso does warn that continued use past recommended OCI in high soot and high shear can degrade it.
Sorry if I couldn't be more specific.
Jerry
Roger,
back when we had on site condition monitoring, one of the more switched on analysts decided to track the viscosity in one of the diesel bulldozers at work.
The oil was a big brand name downunder, beong marletted as "The oil that protects".
It dropped about 15% of its viscosity in the first few weeks of service, then thickened up as the soot loading increased.
back when we had on site condition monitoring, one of the more switched on analysts decided to track the viscosity in one of the diesel bulldozers at work.
The oil was a big brand name downunder, beong marletted as "The oil that protects".
It dropped about 15% of its viscosity in the first few weeks of service, then thickened up as the soot loading increased.
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Is there any advantage in using HDEO that is also API SL rated in a gasoline engine that is not particularly hard on oil? I notice it costs a little more than normal motor oil. Is there something in it that makes it a little better? I sort of figured there is something more being paid for and it makes me wonder if it might do well in a gasoline application as compared to non-HDEO. I would appreciate some comeback on this.
[ February 15, 2004, 08:08 AM: Message edited by: krholm ]
[ February 15, 2004, 08:08 AM: Message edited by: krholm ]
Since most HDEO's are dual-certified such as CI-4/SL, that's a good question. Here is what a HDEO has that a regular "starburst" oil will never have:
1. Extra additives to deal with high soot environments in modern emission-controlled HD diesel motors: detergents/dispersants far beyond what just an SL oil can provide.
2. Extra additives to deal with newer HD diesel motors with redesigned pistons that moved the Ring Land much closer to the Crown Land: the additives prevent Top Grove Fill and ring sticking/breaking.
3. Extra protection at high temps, as most HD diesel motors are turbocharged. In particular, the Ring Land area can see +600 F under full load and 100% turbo.
4. For regular 15W-40 oils, the polymer additives are carefully selected to minimise shearing, as most HD diesel motors operate HEUI, which places severe shearing forces on an oil.
5. All other things being equal, the slightly heavier 15W-40 will lower oil consumption while having minimal or nil effect on fuel economy.
I've run HDEO's in all my personal cars and have noticed minimal to nil difference in fuel economy. I would like to try this theory out on something like a Honda Civic that already gets 40 MPG, just to see if lighter oils are CAFE nonsense or truly energy efficient.
As an extreme example, I bought new a 1990 Toyota 4Runner with 3.0 V6. Running Mobil 1 5W-30 and then Mobil 1 15W-50, there was NO difference in fuel economy. But the 15W-50 made the motor almost silent, no "tickticktick" noises whatsoever.
There has been some concern about the additives in HDEO "poisoning" the catalytic convertor and O2 sensors. Since most HDEO's carry SL ratings, I very much doubt that.
And since a 5W-40 or 15W-40 will usually cause a dramatic lowering of oil vapor passed into the exhaust stream, the cat and O2 sensors should last longer.
In the end, I would say a HDEO is far better in most engine environments. At the very least, the motor will stay cleaner and use less oil, even if you extend the OCI.
Jerry
1. Extra additives to deal with high soot environments in modern emission-controlled HD diesel motors: detergents/dispersants far beyond what just an SL oil can provide.
2. Extra additives to deal with newer HD diesel motors with redesigned pistons that moved the Ring Land much closer to the Crown Land: the additives prevent Top Grove Fill and ring sticking/breaking.
3. Extra protection at high temps, as most HD diesel motors are turbocharged. In particular, the Ring Land area can see +600 F under full load and 100% turbo.
4. For regular 15W-40 oils, the polymer additives are carefully selected to minimise shearing, as most HD diesel motors operate HEUI, which places severe shearing forces on an oil.
5. All other things being equal, the slightly heavier 15W-40 will lower oil consumption while having minimal or nil effect on fuel economy.
I've run HDEO's in all my personal cars and have noticed minimal to nil difference in fuel economy. I would like to try this theory out on something like a Honda Civic that already gets 40 MPG, just to see if lighter oils are CAFE nonsense or truly energy efficient.
As an extreme example, I bought new a 1990 Toyota 4Runner with 3.0 V6. Running Mobil 1 5W-30 and then Mobil 1 15W-50, there was NO difference in fuel economy. But the 15W-50 made the motor almost silent, no "tickticktick" noises whatsoever.
There has been some concern about the additives in HDEO "poisoning" the catalytic convertor and O2 sensors. Since most HDEO's carry SL ratings, I very much doubt that.
And since a 5W-40 or 15W-40 will usually cause a dramatic lowering of oil vapor passed into the exhaust stream, the cat and O2 sensors should last longer.
In the end, I would say a HDEO is far better in most engine environments. At the very least, the motor will stay cleaner and use less oil, even if you extend the OCI.
Jerry
I would imagine that all of the CI-4 oils made in the US maintain their viscity pretty well. I've tested several bolivian, brazilian, and argentine oils that lost viscosity by 150 hours and then started thickening up. Notable was Pennzoil Long Life when they produced it here. I've analized 100 or more samples of Delo and not found them thin or thick. The better group I's thicken up after 400 hours or so.
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