Originally Posted by SubieRubyRoo
TBN going to be a waste with 4 qts of makeup oil, not going to be accurate measure of acids.
Other than that minor detail, report looks almost too good to be true at nearly 200k miles!
On vehicles with a fuel consumption of 100 km an oil consumption of 0.5 liters/1000 km is acceptable.
On vehicles with a fuel consumption of >40 liters/100 km an oil consumption of 0.25 % relative to fuel consumption is acceptable.
Limit values for the engine:
An oil consumption of 0.5 % relative to fuel consumption is acceptable.
Quotation from workshop manual for my Unimog U500.
Re oil consumption it is what it is. Mine has been 1L/2500mi since new, no changes, 0.09% of fuel consumption. It is still valuable to do a UOA to monitor if the oil is still serviceable; a higher rate of consumption allows the oil to stay serviceable much longer, all other factors held equal. As far as monitoring for unusual wear patterns, a change in elemental concentration is still detectable. I really do not understand the assertion that consumption/replacement of oil makes acid measurement "not accurate", Naturally acidity will rise and alkalinity drop more slowly with oil consumption and replacement - a good thing, right?
On my last UOA at 25000 mi I determined that I could try for 40k mi next time. TBN was 11.5, Fe 36, viscosity still 13.0 with 5W40.
Basically, engines with larger sumps and higher rates of oil consumption NOT due to wear (i.e. since new) con tolerate very long OCIs.