In my opinion you're fine. But I agree that the piston is way too clean, should be almost coated in a dark brown color. I would richen it up a tad if that's what it looks like after running it.

Any discoloration (brown, gold or black) means you're not running castor oil. I run castor oil in all my engines 2% and they are clean just like new condition. Castor oil promotes better engine life.

Yeah, but 2% is no 6% as the topic starter mentioned. Or he has a very well degummed castor oil or his castor was realy a (half) synthetic.

It's been my experience that castor oil in nitro fuel leaves your piston a dark honey color. The more castor the darker the color.

Totally WRONG! castor oil has a real high flash point ICSC 1452 - CASTOR OIL (inchem.org) Any discoloring is from the lack of castor oil. Les oil lube will causes burring color with no castor oil 8-12 % oil lube. I run 15% nitro with 18% oil lube and 2% castor and get no burning or discoloring.

Stop the crap, your 2% castor is falling into nothing with your 18% oil and basically that is no fuel any competition engine will see. Any normal fuel with a large content of castor will give a brown to black color in any competition engine. And another thing, what is your experience with real onroad racing engines? The higher comperssion and the hotter combustions compared with any RTR engine is also making a difference.

You stop your crap with the fuel I use. I use Omega fuel off the shelf .with 2% castor oi. It isn't going to leave any brownish color in any nitro engine. I have been running nitro for 30 yrs. with no affect running castor oil. Low oil lube will burn any nitro engine up fast and cost you more money. Fuel is fuel It all burns. What really matters is the oil lube to protect the life of the engine.

You didn't bother to look at the facts! castor oil flash point 229C, nitro flashpoint 35c and methanol flash point 12C How can castor oil burn if nitro and methenol have a low flash point????????

I've been playing with nitro motors for 60 years. so what? The more castor you have in there the browner it gets... your 2% castor doesn't amount to nothing. Put enough castor in there to do some good and you'll see brown on your piston.

So it is all of us having the wrong experience compared to yours?

You can provide us with all kind of scientific numbers but the one castor oil isn't the other. Take Shell Racing M, the best performing oil I have seen due itts SAE30 specs but the engine will turn totally black inside. I also have runned Castrol M50 (later named to Racing M as well) and Eurol Racing-1. They seem to be the same with the same results like a pretty clean light brown color.
And sometimes it is not the oil itself causing the black layer but from the polution inside the oil, it is hard to get castor 100% clean. It is the synthetic oil that is made to give a clean combustion for less engine maintenance.

And talking about your flashpoint numbers..... How hot does it become inside the engine? You do not know.... I can only say that our 48.000 rpm and higher compression will give our engines a much higher combustion temperature than your monster truck engine.

Hello 1995 Monster T,

Castor Oil flash point is at 229ºC. But as Roelof said that the heat at the combustion point/center surely exceeding 229ºC.

I had the experience of using Runner Time fuel for some time. It has full 9% Castor Lubricating Oil, and the Piston Head comes out brown to black after 60 minutes Final. At the moment I am running VP Tessmann Edition Fuel that run propretiary 7% Full Synthetic Lubricating Oil and the Piston Head is not as brownish as with Runner Time.

Cheers.. :)

Both of you can drop???? Castor oil doesn't burn at operating temperature not even under compression. Your engine would melt down before it would reach 229C. The discoloring if from something else burning. Castor oil doesn't burn until 229C.

Huh? melting point of aluminum is at 660C, brass even much higher so how would it melt at 229C

About combustion temps: http://fluid.wme.pwr.wroc.pl/~spalan...combustion.pdf

Yes, the oil is not the the one that combust but because it is within the mixture and on the surface of the piston it will be in the flame of the combustion and burn.

Aluminum expands @ 229 C to remove engine bearings easy But a engine will never get that hot under normal operating temperature. Not even close. Fuel without castor oil will discolor after burning. So it isn't castor oil that burns. It's the ingredients that the manufacture puts in the oil lube blend that is causing the burn. I have used may brands of fuel with and without castor oil . Sig, Redmax, Omega, Byron(crap) Wildcat and S$W. Non of these I nave never seen burning.. So it comes down to the brand and blend! So you can keep on blaming castor oil for the burning but it doesn't BURN under operating temperatures! I have even started making my own blend of fuel. Only 3-4 ingredients. No burning yet.

Can you please make up your mind...

There is always fighting on this forum for some reason.
By the way more castor you have in fuel more darker piston gets. It's 2+2 = 4.