The text below was submitted by a Model Engine News reader in May after reading the FCB Marshall piece on model engine fuels. He raises some good questions to which I have no good responses, so I have decided to break the long-standing MEN tradition and publish the dreaded "letter to the editor" (rest assured, I won't make a habit of it). The subject is certainly worthy of more study and experiment. After all, wouldn't it be a blast to run an engine on a laxitive? (sorry 'bout that chief...)

Ron C, June 2007


Kerosine, Kerosene, and Paraffin

I have just had a brief scan of the recent article Miniature Engine Fuels By FCB Marshall. I noted in your preface that you mention "paraffin was the popular name in England for what most of the rest of the world would call kerosene". I have been confused by these claims since acquiring my lathe this year and reading many tips on machining Aluminium that call for 'Paraffin' as a lubricant/coolant, and then some that call for 'Kerosine/Kerosene' as a lubricant, and then others that say they are one-and-the-same. Originally I had no idea what paraffin was (except for paraffin wax) so tried to find out. To say I'm more confused now than ever is an understatement!

In my meagre library (compared to yours!) I have a book titled Dictionary of Energy Technology by Alan Gilpin, an English publication with an Australian author. It's a brilliant book, but sometimes vague. Here is his definition for 'Kerosine':

'Kerosine - A petroleum fraction of light distillate fuel, with a boiling range 150-280°C and a specific gravity of 0.78-0.82. It is used for heating, in aviation gas turbines, and in some industrial gas turbines. It is similar to paraffin as used in domestic burners; it is very largely a mixture of paraffins, isoparaffins and napthenes containing up to 18 per cent weight of aromatic compounds'

The definition for paraffin is vague, but does say it's used for lighting and heating and also mentions "..a hydrocarbon belonging to the methane series". There's no mention of turbines for the paraffin, and there's no mention of the "methane series" for the kerosine. Neither say 'see kerosine', nor 'see paraffin'. After reading this I figured 'similar' is good enough and used kerosene as a cutting fluid mixed 50/50 with a light machine oil (like 'Singer') However, 'similar' is not 'the same as' which many others claim, which also got me wondering.

Months later while in a local IGA store [Independant Grocers' Alliance, Ed], I spotted a small bottle marked "Paraffin" with the small type Oral liquid for use as a laxative. The liquid is clear (kero is too of course, being coloured for general public use) and more viscous than Kero, very much like baby oil but maybe a little more viscous. It does 'seem' to work better when machining Aluminium. The bottle is packaged by Faulding Pharmaceuticals so I went to their website, got redirected to Mayne Pharmaceuticals where a search promptly drew a blank! Figures.

I then dug deeper. Wikipedia's listing for Paraffin and Kerosine confirms they are different. But the paraffin listing does mention that for the fuel, see kerosene, however it then later mentions that liquid paraffin is used as a fuel! Confusion! It also mentions paraffin can be methane based, as my dictionary did, with a single carbon atom per molecule thru to eight carbon atoms. No mention for kero of methane, but it mentions molecules containing between 12 and 15 Carbon atoms for kero.

There is a link from 'paraffin' to 'paraffin oil' which gets redirected to 'Kerosine', but there is also a link to 'Mineral Oil' in which there's a list of also-know-as (AKA's) which include:

Hmmm, more confusion, though I'm pretty certain the mineral oil wiki-listing is not claiming that they are all the same, as they're clearly not!

The Material Data Safety Sheets (MSDS) for the two are also confusing, Paraffin OIL, AKA: Mineral oil, is obviously not the 'Paraffin' that is taken orally like the bottle I have, as it mentions it's not to be ingested!. But it does say it is flammable with a flashpoint of 193°C and can explode in a vapour/air mix (like most things). The MSDS reference for Kerosene is quite different from Paraffin Oil with a flash point of 38°C and an autoignition temperature of 210°C. FCB says approx 250°C for paraffin oil which is pretty close to the Kero.

All this has got me pretty seriously confused, but through the confusion I can see that paraffin oil and kero must indeed be different fuels. Whether the Paraffin oil I have is the same paraffin oil, I have no idea.

I've also got to wondering how all this confusion has come about. Was 'real' paraffin oil—apparently okay as a fuel—trully used as a heater/burner fuel in the UK, like the energy dictionary says, then sometime later substituted with kero but the name has stuck? Was Paraffin oil used in the UK, possibly STILL used in the UK, but assumed by people of other nationalities to be the same as Kero as used in those other countries for the same purpose? I can remember when home oil-heaters in Australia were still in common use, with the large tank mounted on an outside wall. The liquid didn't appear to be the same as kero, tho I was pretty young at the time. Could this have been paraffin oil? I can also remember the 'portable' heaters that did use kero. Is it possible that the 'real' paraffin oil, if really used in the UK at one time, or still, was also used in the model 'Diesel' fuels there?

Which brings me to the main thrust of this email (the long way). I wonder if yourself or one of your readers, would like to try a comparison of the two in 'Diesel' fuel. It would be interesting to see if the paraffin oil makes for a different fuel, or if it even works at all. I would do it myself if I could immediately fix two shortcomings: a source of ethyl ether, and a working 'Diesel' engine!

Anyway, thanks for reading through my rant, sorry if your now as confused as I am, but hopefully it has inspired you or a reader to try using 'real' Paraffin as a fuel... It will be interesting to see what the results are.

Thanks again,
Simon Williams

 


Afterword

Simon's questions produced some very good feedback from a number of other readers. As a result, we can say that no, the little bottle of "Paraffin" laxative should not be fed to your engine. But kerosene is not paraffin either. See the August 2008 issue of Model Engine News for the last word on the subject (hope it's not the Fameous Last Word).

 

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