Molakule;
That nitration comment got me thinkin'.
A product of combustion (somethin' like NOx in smog production?) and common to gasious fueled engines.
LPG and CNG both?
The reason of my interest is because every LPG engine I have ever built has consumed some engine oil.
Some of those engines were broken-in on gasoline then converted to LPG and started using about one litre every 2500 miles on average there after.
It is a well known fact around here, at least at one time, that engines re-built intended for LPG fueled vehicles needed special attention to top ring position and end-gap.
The reason was assumed to be that LPG ran the pistons hotter. (bad race-pit English, I know)
Sometimes the learning curve was expensive.
Some machine shops used a performance piston with a very high top ring position, and found out the hard way.
Reading the instructions might have helped a lot, but have you ever delt with a machine shop owner that has been in business for 40 years, and knows everything there is to know about everything?
Or does that describe most of them?
Back to the nitration question...
Do you or Al think that nitration is the reason for LPG engines' oil consumption?
Here is an industrial example of this:
We on the railroad have several one ton vans, Chev and Ford that are used to dead-head train crews.
Those vans put on about 8-12,000 miles a month, and some of them have over one million miles on the original engines. SBC 350s and SBF 351Ws.
The oil consumption has been flat for the last several years at around one litre every 2-3,000 miles.
With my own LPG vehicles, I re-built the engines with cast hyperutectic FM pistons at .0025".
A little on the loose side, but not enough to cause cold engine piston slap.
It did not matter which brand, synthetic or not, 20W50, 15w50, sae 40, or junk-mart 5W30, the engine oil consumption remained about the same.
The railroad crew vans get their oil changed about once every 3 or 4 months, by the drivers.
I usually poke through the box in the back to see what they use, and the oil brands and types are not exotics nor are the filters.
Whatdaya think?