oil stress in kwh/gm:
(1/R) * (1 - exp(-Rt/V))
R is specific oil consumption in gm/kwh
t is time in hrs
V is specific oil volume in gm/kw
You have to figure out actual average power output by working backwards from average speed (available on newer vehicles electronic systems, or miles/hrs) and fuel consumption per kwh. 220gm/kwh is a good number for a direct injection diesel, their best is ~200 but figure inefficiency increases with partial load and varying rpm. On my Unimog I came up with 69 kw (peak is 191) average power output and R = 0.175gm/kwh. V for the Unimog is 370 gm/kw with a 29.6L sump, for the BMW X5 (7L sump) it is 270 at 22 kw average output ( max 205kw) , average speed 30 mph
So max possible OSF for the Unimog if I never change the oil and just add 1L every 2500 mi and average 35 mph and 8-9 mpg is 5.7. 1200 hrs (max MB recommendation) would be 2.55, 800 hrs 1.9
On a vehicle like the BMW with zero apparent consumption the equation simplifies to OSF = t/V
So 10K mi on that vehicle is 330 hrs, OSF 1.22. That wiped out weak LL04 oil but Delvac 1 5W30 LE worked well.
At 500 hrs, OSF of 1.5 Delvac 1 SHC 5W40 in the Unimog still had TBN 12.4, Fe only 36ppm
So I am figuring with an OSF of 2.55, even with 350ppm S Russian fuel and 3000ppm Mongolian fuel that TBN will still be 7-9
Actually, at the asymptote of 5.7 Fe should level out at 140ppm, still below condemnation limit of 200ppm, and on North American fuel TBN should level out at 4. The unknown would be breakdown of the base oils with thickening, even though it is a PAO based synthetic. Not worth risking a >$15-20K engine.
Taken from paper:
Oil stress investigations in Shell’s medium speed
laboratory engine
Julian Barnes, Shell Global Solutions, Germany
[email protected]
Jan Hengeveld, Shell Global Solutions, Germany
Simon Foster, Shell International Petroleum Company, United Kingdom
Thijs Schasfoort, Shell Global Solutions, Germany
Rinie Scheele, Shell Global Solutions, Germany
Charlie
(1/R) * (1 - exp(-Rt/V))
R is specific oil consumption in gm/kwh
t is time in hrs
V is specific oil volume in gm/kw
You have to figure out actual average power output by working backwards from average speed (available on newer vehicles electronic systems, or miles/hrs) and fuel consumption per kwh. 220gm/kwh is a good number for a direct injection diesel, their best is ~200 but figure inefficiency increases with partial load and varying rpm. On my Unimog I came up with 69 kw (peak is 191) average power output and R = 0.175gm/kwh. V for the Unimog is 370 gm/kw with a 29.6L sump, for the BMW X5 (7L sump) it is 270 at 22 kw average output ( max 205kw) , average speed 30 mph
So max possible OSF for the Unimog if I never change the oil and just add 1L every 2500 mi and average 35 mph and 8-9 mpg is 5.7. 1200 hrs (max MB recommendation) would be 2.55, 800 hrs 1.9
On a vehicle like the BMW with zero apparent consumption the equation simplifies to OSF = t/V
So 10K mi on that vehicle is 330 hrs, OSF 1.22. That wiped out weak LL04 oil but Delvac 1 5W30 LE worked well.
At 500 hrs, OSF of 1.5 Delvac 1 SHC 5W40 in the Unimog still had TBN 12.4, Fe only 36ppm
So I am figuring with an OSF of 2.55, even with 350ppm S Russian fuel and 3000ppm Mongolian fuel that TBN will still be 7-9
Actually, at the asymptote of 5.7 Fe should level out at 140ppm, still below condemnation limit of 200ppm, and on North American fuel TBN should level out at 4. The unknown would be breakdown of the base oils with thickening, even though it is a PAO based synthetic. Not worth risking a >$15-20K engine.
Taken from paper:
Oil stress investigations in Shell’s medium speed
laboratory engine
Julian Barnes, Shell Global Solutions, Germany
[email protected]
Jan Hengeveld, Shell Global Solutions, Germany
Simon Foster, Shell International Petroleum Company, United Kingdom
Thijs Schasfoort, Shell Global Solutions, Germany
Rinie Scheele, Shell Global Solutions, Germany
Charlie
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