currently we are using SHELL Mysella LA40 for lubrication of our Gas generator which we drain after 1000 hours.can anyone suggest oil so that our drain interval will increase

Just as replied to your diesel application..

Another way to help with the extended drain interval is to make sure your filtration is highly affective. I am not associated with this product but have used it personally and in a few applications with work. Amsoil makes a very god bypass filter / main filter unit that can go down to about 1 micron. The main doesn't filter that fine, but it is the bypass portion. I'm also not sold on a brand because I have used several, but running a synthetic oil can dramatically improve the drain interval. Using this type of a set up, intervals can be increased by as much as 300%. But it can not be stressed enough how important oil analysis is.

Dean,
I could not agree more about the oil analysis. Imranirfan, if your objective is to extend the drain interval, first you need Oil analysis of the new oil, at least four samples of in-service oil analysis at 500 hr intervals to determine Vis, Spectro Metals, %soot, Water, Oxidation, TAN, TBN, pore blockage particle count, and one Drain (end if life)sample for varnish potential.

If these samples are within the guidelines of fit for continued service, except for particle count and soot, then investigate side-stream or kidney loop filters. Continue to sample the oil.

If the soot, water, TBN, and particle count, and all other elements are quantatatively more within limits, following the addition of kidney loop filters, then continue testing while extending the drain interval by small increments.

Please remember to change ate filters every time the oil is changed, or as advised by the filter manufacturer.

For Varnish testing I Know analysts Inc provides this service. See http://www.analystsinc.com

Good luck

My experience with the Mysela LA here in Bolivia is very high nitration and very short life. The best thing you can do with a gas engine is move to a good group II oil. I once sold Chevron products and analyzed hundreds of samples of it and others. If you can get their HDAX Low Ash (you mention Chevron in another post), I can recommend it for long drains, as long as your head temperatures are correct and mixture is correct. I have uncounted hours/weeks in that project.
I have documented double the hours with half the nitration using HDAX over Mysella.

Just for the record as an ex Shell man, and without disagreeing with other comments Mysella LA is Ok with the limitations stated. Gp 11 base oils not readily available everywhere.
You might try Mysella XL (low ash)with claims of double the oil life.
As with all gas engines, regular monitoring is helpful.(necessary)
I assume you are using natural gas or similar as apposed to landfill/sewer gas where different oils are required.