There are two components in this problem. One the Engine and other the oil.
1. Waukesha is a well known brand (possibly the best in Gas engines) used widely on Rigs, Drilling, Power Plant etc. No doubt you would have taken some advice from the OEM on the above problem.
2. The second factor is the lube oil. Mobil possibly the undiputed leader in lubricating Gas engines. Castrol has the NG (Natural Gas series) but not not used widely, except possibly with a variant in France.
3. The extension of life of lube oil in an engine, whatever the application, will depend on 5 major factors and indicative discard or drain periods to be used as a thumb-rule (according to Wartsila - with HFO as fuel) are as follows:
a) Viscosity of oil - Discard level + 45% change in original Viscosity at 40 Deg C. or - 25% decrease in KV 40 compared to original viscosity.
b) TBN - Discard at 50 depletion compared to original TBN.
c)Water - Discard at 0.3% Max by volume
d)Insolubles - Discard at 2.0% wt %
e)Flash Point - Min 170 deg (PMCC)
approx 190 deg (COC)
Have the oil tested by you reached these limits?
Hussam Adeni