oil consumption question

[RF Overlord]

We have a Cummins 6 cyl natural gas engine that's part of an Onan 250kW standby generator. We bought it new in Oct of '03 and it now has approx 66 hours on it. The factory fill for this motor was Cummins Premium Blue, which I understand is made by Valvoline. I've been topping it off with Delvac 1300S 15W-40, which is the recommended viscosity, according to the manual. At the most recent oil change (its first), the maintenance company put in Rotella 15W-40 and now it seems to be using oil at a faster rate than it did before the oil change.

Is it possible for this motor to consume more oil using Rotella than Delvac, even though they are both the same viscosity? Or am I hallucinating...?

 

[kenneth neeley]

No, it is the Rotella. Working with genset everyday we find people who even put SJ "auto" oil in the engines. A natural gas engine requires a different additive package. You can get by with running Mobil, Cat, and some other HDEO but not Rotella. Most oil companies make a monograde natural gas engine oil. Cat's oil is what we use. Also does the genset have much load or is it ran unloaded during excer. tests. No load or light loading will lead to slobbering and oil loss. Ken.

 

[RF Overlord]

Ken, thanks for your insight.

This genset is exercised for approx ½ hour a week with no load (we're a cable TV company and switching the load creates momentary outages that are unacceptable).

The manual states that Cummins doesn't recommend any specific brand of oil, only that it be the correct viscosity for the operating conditions (in our case, 15W-40) and meets certain specs (Cummins 20076, I believe, which both Delvac and Rotella claim they do).

Once the left-over Rotella is gone, I'm going to return to using Delvac 1300 for top-offs, and tell the maintenance people not to use Rotella anymore.

 

[Dick in Falls Church]

Try the AMSOIL natural gas engine oil. Sample it yearly, and you might be surprised.
Contact any of the AMSOIL site supporters.

 

[RF Overlord]

****, I'm sure the AMSOIL product would be excellent, but I highly doubt I could get my company to authorise it. They just go with whatever the maintenance contractor puts in, figuring that if something goes wrong, the maintenance contractor is responsible. I've tried to make them listen to reason before, and it's not happening...

Also, the oil gets changed yearly regardless of hours (or lack of), so extended drain capability is not a requirement.

 

[tom slick]

I think shaeffers makes a CNG specific oil.

my company bought a backup generator powered by diesel with a 100 gallon tank. I wish they would have bought a CNG powered generator due to not having to "maintain" the fuel. we ended up installing a dispensing nozzle on the tank to refuel the one diesel truck we have so that we can exchange the fuel once in awhile to keep it from going bad.

 

[salesrep]

http://www.schaefferoil.com/datapdf/114.pdf

 

[kenneth neeley]

Try running test underload, or yet have a loadbank test ran to see if the rings are becoming unseated.