VP Powermaster RC 30% nitro 9% Synthetic Castor Oil

When I've used full synthetic, my oil content was 24%. In addition, for the nitro percentages I was using, castor oil wouldn't blend with the fuel. It literally laid on top of it . It reminded me when my wife makes salad dressing. I'm a big fan of Powermaster fuels.

Hi Ken, what percentage of nitro you use?

Thanks olenginerod
I will top up another 11% Castor to hit the 20% mark.

Thanks
Ice

I used 45% nitro to 65%. Nowadays due to the cost of nitro, I keep it around 30%. It was around 40% when I started to notice the oil not wanting to mix. Some suggested to me to add acetone to help with insuring the oil mixes with the fuel. I never tried this. When I would pour in Klotz synthetic or even the 20% castor /synthetic mix it would instantly blend.

Ken Cook wrote:I used 45% nitro to 65%. Nowadays due to the cost of nitro, I keep it around 30%. It was around 40% when I started to notice the oil not wanting to mix. Some suggested to me to add acetone to help with insuring the oil mixes with the fuel. I never tried this. When I would pour in Klotz synthetic or even the 20% castor /synthetic mix it would instantly blend.

This makes sense-the critical % of nitro is around 45%-when it comes to castor mixing...and that will be slightly influenced by methanol purity, temperature and other factors....including whether the castor is 'straight' or has had some post extraction chemical modification. As Ken notes-a small amount of acetone added...[from my own experiments as little as 2% v/v] can solve your miscibility problems.

I used to use 50% nitro in my Payload models....and these were only flown at our Nats....so once a year. It was fairly normal to find -during Nats preparation...that the fuel had separated into two layers on standing unused for months. A bit of careful sequential addition of acetone and vigorous shaking followed by some settling time sorted it out. I did add it sequentially a few mls at a time to minimise the dilution of the nitro %...obviously there's no point in adding 5% acetone if 2% does the trick.

I don't know if anyone has done the systematic test of mix ratios of synthetic:castor in Coxes; I am aware of one past study involving all synthetic [I think it was posted on the 049 Collectors forum when that still existed] where the poster claimed no problem encountered with running full synthetics.....most of us I suspect would be happier with some castor in the mix....but I'm unaware of any hard data on say 5%, 10% 20% 50% etc
-though I imagine Cox themselves probably did some work in this area when synthetics first became an option in the mid to late 60s

You would need a lot of work-and very good equipment-to come up with any repeatable systematic measurements; not to mention how you go about defining 'acceptable wear' for the purposes of overall assessment of the effectiveness of the lubricant component of the fuel

ChrisM
'ffkiwi'