For the last 10k miles, I've been using a Heavy Duty (Diesel) Engine Oil called Amsoil ACD in my VW GTI 1.8T. It has high levels of metallic containing additives that form ash when burned. This is quantified in the sulfated ash test. In general, the ash builds up on spark plugs and some other parts of the combustion chamber.
My engine has 106K miles on it now and I've been monitoring the spark plug and piston top deposits every time I've changed the plugs. When I changed and looked at the plugs used while using Amsoil ACD, the spark plugs did not have any more deposits than they did while using passenger car motor oils. The piston top deposits were lower than it was the time I checked it before.
I should note that Amsoil ACD has cut back the oil consumption from minor to undetectable, so that probably is why the piston top deposits are improved now.
So just because one changes to an oil with higher sulfated ash does not mean that ash deposits in the combustion chamber will increase. In my case, they were overall decreased!
My engine has 106K miles on it now and I've been monitoring the spark plug and piston top deposits every time I've changed the plugs. When I changed and looked at the plugs used while using Amsoil ACD, the spark plugs did not have any more deposits than they did while using passenger car motor oils. The piston top deposits were lower than it was the time I checked it before.
I should note that Amsoil ACD has cut back the oil consumption from minor to undetectable, so that probably is why the piston top deposits are improved now.
So just because one changes to an oil with higher sulfated ash does not mean that ash deposits in the combustion chamber will increase. In my case, they were overall decreased!