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Many interesting topics were covered this month by the world-wide members of the internet Stationary Engine Mailing List and one which was brought to my attention as a suitable subject for the GEM article discussed 'snobbery' at engine shows. The attitude of some show organisers and exhibitors inspire some lively discussion, but as last month's article was on the subject of shows, I decided to save that for next month and pass on some brief, but interesting, information about oils for lubrication.

Strangely, this thread started life when someone asked the off-topic question of how he could get rid of gophers on his property, and one suggestion offered the use of a Maytag exhaust inserted into the offending hole, with the addition of various substances to the running mixture of the engine. This then developed into querying which additives can safely be used with stationary engines.

Before I go and try this I want to make sure. ... If I empty the oiler on one of my engines and put castor oil in there it's not gonna seize the piston or burn up the cylinder? I bought some castor oil last time this was brought up but never did try it because I wasn't sure if I'd screw anything up.

Nope. It'll run great. The worst that can happen to you with castor oil is stuck rings, but that happens primarily with long running under very hot conditions. Castor oil has better anti-friction properties than the old straight mineral oils, and excellent antis cuffing properties under high bearing loads. Lots of oils for racing two-stroke motorcycle engines are still based on castor oil.

You shouldn't mix mineral and vegetable oil together, as the vegetable oil goes into lumps and can block oil-ways.

There are special flushing oils required to change from one to the other, and unless you are racing there is not a lot of point in using vegetable oil in the first place.

All true enough, but there's not really a lot of point in any of this stuff that we do, is there? With a drip oiled piston, I believe that simply emptying out the oiler and changing over will work okay either way.

Intriguing statement . . . Why would racing make a difference?

Because vegetable oils had better performance at high temperatures than mineral oils. Fully synthetic oils may have reduced the gap, but you tend to find most air-cooled engines such as bikes on vegetable oil, while cars, etc. tend to use 'normal oils.'

Castrol used to have an information leaflet on the subject, and I remember our little cafe-racer group in the 1960s having all sorts of problems with cleaning out vegetable oil after use. Not many solvents will touch it.

Mixing them is a big no-no and has grenaded more than a few bikes. I buy Blendzall and run it really lean in my gas for the desired effect... no ill effects so far. Drip oiler is still used as normal.

I think the point of using it is to stimulate an old Pavlovian adrenal response.

It's probably worth discriminating between castor oil and vegetable oil as much as we can; there are differences.

Castor oil is indeed a vegetable oil, but as far as I know it's unique in containing a fatty acid (ricinoleic acid) with hydroxyl groups on the chains. They're somewhat polar and cause castor oil to cling more strongly to metals than hydrocarbon or normal fatty oils.

As I know it, Castor oil is a 'boundary lubricant' and holds on under pressure better than the old mineral oils. This was pertinent in the early days but, now the modern oils with all the different additives are far superior to straight castor oil; there is no point in using it. If you like the smell, drip some on the hot exhaust!!

Castor oil doesn't dissolve in petroleum solvents, by the way, but citrus oil or turpentine works fine if you need a thinner or solvent for some reason.

A short and sweet article this month, but for those for whom the faint aroma of castor oil drifting over the show ground brings back happy memories of racing days, it seems it's possible to achieve without doing any damage to antique engines.

This coming month should be very interesting engine-wise here in the UK. We have our biggest national rally in 3 weeks, which has, so far, escaped from the threat of Foot and Mouth disease which has seen many rallies cancelled this summer. Hopefully, this rally will be a taster for the Portland, Indiana show, as there will be a meeting of English, American and Dutch members of the mailing list, showing English, Danish, American and Czech engines. There will also be an exciting addition to our personal engine collection, a night-time show to celebrate the summer solstice and a city centre show to mark the opening of a new Space and Science centre, celebrating technology of the past and present. I'll keep you informed!