Oil for engines running LPG, CNG, or Propane

Originally Posted By: Rob_Roy
Originally Posted By: Loobed
There is nothing special in their PDS


Take a look at the ash content.



Propane produces a lot of water. Would the reduction in sulfated ash reduce the formation of acids?
 
IIRC those engines combustion burn hotter and require different ash levels?
 
That might be part of the issue, too, 3311. However, when running a propane taxi fleet, I never bothered with any CNG/LPG/Propane oils. It was simple Quaker State conventional 10w-30 at 6,000 mile OCIs.

The biggest issue on propane at the time was the same as the introduction of unleaded gas. Hardened valves of the time weren't as "hard" as they should be, and in the early years, didn't stand up as well as they should have, whether on unleaded or on propane. Heat might have been a bit of an issue, but there certainly was no problem with carbon deposits.
 
Gas engine oils are formulated for low or no ash. Ash deposits in the combustion chambers form over time and lead to detonation or preignition in high-BMEP gas engines. Since most gaseous fuels have no sulfur, high TBN is not needed, so the oils can be formulated to produce no or very little ash. The main problem with converting gasoline engines to run on propane or natural gas is intake valve seat wear due to "dry" conditions in the intake system. Hard valve seats are required; materials such as Stellite or Triballoy are popular in such applications.
 
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Also, the mention about not using diesel oil in an LPG/CNG engine is a bit odd, and certainly has no context. I would certainly advise against using a diesel only engine oil in a sparker. Do they mean not to use the latest diesel specs? When was the quote written?

Back in the day, most PCMOs had a diesel specification as well, and were used without issues in propane engines.
 
Originally Posted by pep808
but less ash, means also less zinc ?

It can, and usually will mean less zinc, but not necessarily. Zinc content reduction didn't seem to be exactly the point of blending differently for LPG or CNG engines. Nonetheless, I don't think I've seen an LPG/CNG specific lube since before this thread was current.
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It used to be very common to see oils labeled as suitable for CNG and LPG here in NZ. The 2 white diamonds on this label.

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Here, it's been mentioned on data sheets, and most PCMOs indicated suitability. Some oil companies did market LPG/CNG specific oils (Petro-Canada may still), but I have never seen them available at retail.
 
Very popular option on some Italian models, can be ordered from factory when purchasing a new car. Perhaps a member in Italy could enlighten us?
 
Originally Posted by Garak

Nonetheless, I don't think I've seen an LPG/CNG specific lube since before this thread was current.
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Me neither. We maintained a fleet of LPG trucks in the '70's. We put the same oil in them as other gas trucks. Oil and spark plugs came out clean every time.
 
Looking at Petro-Canada's site right now, I can't even find them any longer. They revamped the site ages ago, but they also might have discontinued the product. I can still find dedicated oils for natural gas stationary engines, but not PCMOs targeted specifically to LPG and CNG. Their Supreme PCMOs still state the following, and always have since I've been reading the sheets:

"SUPREME Motor Oils are recommended for year-round use in gasoline, high ethanol (up to E85), propane and compressed natural gas (CNG) fuelled engines."
 
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