I'm building a dummy load, what oil?

**G6NHU** · Sun 21st Aug 2011, 22:29

Over the course of the weekend I've bought myself an empty paint tin, 30 x 3W 1k5 non-inductive resistors and a couple of brass plates along with an SO239 socket.

Yes, I'm building a dummy load.

That should handle 90 watts in air but of course, that's not enough so I'm going to fill the can with oil.

The question is - What oil? I've found plenty of american sites that just state "mineral oil" with a lot of them suggesting Ace Hardware as being the best place to get it, where it's just a couple of dollars.

Sadly, we don't have an Ace Hardware in the UK and believe it or not, I'm having problems finding what looks like a suitable or similar oil.

I understand that mineral oil is more commonly known as liquid paraffin over here and I've found some places that sell it - This for example at B&Q looks reasonable but it's for burners and heaters so probably has a low flash point which is not something I'm sure I'd want in a dummy load.

There's this on eBay which looks suitable but including the postage, it's about twenty quid which seems somewhat excessive.

I suppose I could just fill it up with some engine oil, but that doesn't appeal to me.

So what are your suggestions for suitable oil for a dummy load that I can pick up in the UK and won't be stupidly expensive?

**5B4AJB** · Sun 21st Aug 2011, 23:34

The mineral oil you need is clear and has a very high flashpoint.
Some overclocked P.C.s used to be cooled with this stuff, I once saw a small fridge containing this oil with a motherboard dipped in it (it's non-conductive).

This might be a good place to start.

**G6NHU** · Sun 21st Aug 2011, 23:38

That article doesn't really say much, yes it explains how it can be used for cooling but it really doesn't help when looking for a UK supplier at a sensible price. I don't need to do this on a budget because it's being done for fun more than anything else but spending twenty quid on the oil when I've only paid out about a tenner for everything else seems a bit crazy.

**G6NHU** · Mon 22nd Aug 2011, 00:17

I've just found this which I'm pretty sure is what I want but although it's nice and cheap, it's still £17 when you take postage into consideration *sigh*

**G6NHU** · Mon 22nd Aug 2011, 00:23

Getting better - This one is £14. Can anyone find a better price, including postage? If I can find it for under a tenner all in then I'll be almost happy!

/edit - That didn't include postage either and works out about the same as the previous one

**K7KBN** · Mon 22nd Aug 2011, 01:19

Posted this once but it didn't register - go to your local electrical utility and ask for a bit less than 4 liters (okay, litres) of PCB-free transformer oil. Over here, the utilities buy it by the barrel, and there's always a bit left in the bottom. They give small quantities like you need away, and showing an amateur license would probably be a plus.

**M6PAP** · Mon 22nd Aug 2011, 09:01

As said by K7KBN in this country they have a small tanker that goes around servicing the transformers and I have seen a Scottish & Southern van with a tank built in to the back.
A good place to find them is when a new industrial/office park is being built!!

mu0chn · Mon 22nd Aug 2011, 17:55

How about using silver sand

**G6NHU** · Mon 22nd Aug 2011, 22:09

I'll keep my eyes open for electricity board vans and see if I can ponce a gallon of transformer oil but in the meantime I found a place that'll sell me a litre of mineral oil for a tenner, shipped. I'm an impatient git and I want this quickly so I ordered it.