Originally Posted By: m37charlie
Originally Posted By: Fraser434
Looks like that low saps oil is offering great protection.....
Also keep in mind TBN goes up/ lubrication goes down, balance of additives.The combustion by product acids are mainly from sulfur. ULSD doesn't need as much TBN; hence low saps, C3, 229.51 oils will have a lower TBN.
Overall you're going to see TBN go down across the board for HDEO looking for better wear numbers.
Not true IMHO. Why does my TBN drop from 10 to 3.5 in 11000 mi burning ULSD, in the BMW? The reason is EGR. With EGR the engine inhales its' own NOx which is very acidic - forms nitrous and nitric acids in combination with water vapor in the exhaust.
OTOH my Unimog sans EGR has TBN drop only from 16 to 12.4 in 17500 mi.
Charlie
The TBN would would be affected more with higher sulfur in the exhaust which would go through the EGR.
It's more than just NOx that goes through the EGR HC, CO,PM, SO2,SO3 etc. The purpose of the EGR is actually to lower NOx levels.
Point is you're not going to see 10+ TBN numbers with newer oils , and don't consider them "weak" because they don't measure 12 TBN. TBN isn't lubrication, it's detergents.