Detergents and dispersents in the context of oils should not be completely lumped in together especially with long drain oils.
Detergents have a much shorter life cycle and evaporate early in the oils life ie 1000-3000 miles. These simply remove formations left over from the previous oil change and pull them into suspension where the dispersents take over and prevent them from rebonding with the engines surfaces.
The reason for a short life of detergency is that it reduces the ability of EP (Extreme Pressure) additives from bonding with the metal surfaces. EP additives are what protect the critical areas that do not rely on boundary layer lubrication ie lifters, pistons skirts, rings etc.
The dispersents live on for the life of the oil and prevent clumping of soot, and retain combustion by-products in suspension in the oil without permitting them to adhere to the inside of the motor. The bigger advantage to dispersents is that they do not prevent the EP additives from bonding to the engines high pressure regions which is critical in achieving the performance required of extended drain oils. Dispersent effectiveness is generally tested using soot loading tests where the concentration of soot is increased to around 8-9% then the engine is run of for 500 hours to see if there is any adverse wear. Dispersents are also the reason why soot remains "dispersed" in the oil and prevents clumping that can result in conglomerated particles large enough to cause damage to the high pressure regions of the motor.
You can to a limited extent lump the two into the same category, however only one remains effective after the initial 1000-3000 miles that being the dispersents.
I am looking ahead to cooler weather oil changes with the 15W-50 oil. Not cold weather, because I will go back to 5W-40 TDT.
Please when and if I get an answer to this, let us drop this subject. I think it might apply to the 5W-40 oil as well but it is just a question and not intended to become a thread off track thing.
The OP in one sense is switching to a higher viscosity oil and the time to drain at oil change time would be longer. I have switched to 15W-50 and the time to have the oil drain down will be much longer. I suppose that the fact that I change with the engine as hot as possible is best.
Now here is sort of how this all fits together. Your statement:
"Detergents have a much shorter life cycle and evaporate early in the oils life ie 1000-3000 miles. These simply remove formations left over from the previous oil change and pull them into suspension where the dispersents take over and prevent them from rebonding with the engines surfaces.
The reason for a short life of detergency is that it reduces the ability of EP (Extreme Pressure) additives from bonding with the metal surfaces. EP additives are what protect the critical areas that do not rely on boundary layer lubrication ie lifters, pistons skirts, rings etc."
Now it would seem to a hick living in Mississippi backwoods that shortly after adding detergents and getting the formations left over into dispersion would be the time to change oil.
Why load the engine up with detergents at the beginning of fresh oil use? Why not add a bottle of detergent right before an oil change (maybe with a new filter) and get the contaminants out of the engine.
Like I say now I am a simple thinking fellow from the back-woods and might not be able to follow logic.
Next, if detergents harm EP additives, why add the detergents right at the time when the new additives are added?
Just being an old red neck. It would seem an oil would have a moderate detergent at foil change time and use a kicker at the end of the oil life to remove the deposits. Just being dumb and all.
So Amsoil sells / does a flush (?). Is this what they do? Help a fellow think through all this.
I do respect your oiling thoughts.
eddif
