Intro: When formulating a 2T racing oil, Castor Oil has been popularly used in most all well known products. Elf, Eni, Klotz, XPS, Maxima, Vroaam, etc have all used Castor at around a 20-25% blend rate. Castor has a solvency issue with most* base oils and will fall out of suspension at around 55F...and once its mixed with racing fuels that have higher alkylate contents and lower RVP values, (which is a large portion of VP, Sunoco and Aspen's product offerings)... then the castor will typically seperate at around room temperature. The most common solution is to use a solvent with a high aromatic content which generates some polarity in the oil blend. These are very cheap, but wreck the viscosity of the finished product blend (without the use of a viscosity modifier like PIB). A better end product would be one formulated without solvents. Note that if you use pump gas for your "racing fuel", these have higher aromatic content, higher RVP,...then solvency becomes a non issue...even to 0 degree F temps. I should also note that a couple of those brands mentioned above have castor separation problems with the above mentioned high alkylate content fuels... I won't name names.
Here are my thoughts on solutions to help solvate the castor w/o wrecking the viscosity:
1. The use of naphthenic base oils helps some... but not much. Perhaps a couple degrees of improvement before separation occurs. A high viscosity naphthenic base oil with a high sulfur content will help some as well.
2. I'll admit, my knowledge of all the different Ester product offerings is limited... Cargill, Dehylube, Exxon, NYCO, etc all make a VAST array of product offerings. These arent cheap. These products have great film strength and help the solvency some*. I'm sure there are some products that help solvency more than others..im not sure which ones though. Some, (or perhaps all) of these may be cost prohibitive base on their blend mix rate. TMP is the most commonly used product for 2T applications. I need to experiment more with these types of base oils and products.
3. King Industries, Exxon, and a few other companies make AN's. I have no experience with these. They tout better solvency. I know they are used at ~10% in some group III and PAO blends to help solvate other additives. I presume the benzene rings present in the solvents that help solvate the castor oil (as mentioned in my intro,) are serving the same purpose as the benzene rings in an AN. This might be a more attractively priced option if it works well.
4. Another option? comment below. Maybe a Polyalkylene Glycol?
Also,
The use of PIBSA is also an option...but the end use of this oil if for engines that rev to 18,000, and the tack properties of PIB have a known problems of inducing too much heat into the big end conrod bearing. These burn clean, but I dont think are a good use for this particular application...maybe for outboard engines...but not racing engines...I'd highly prefer to not use PIBSA. The ~$20-$25/gallon cost is unattractive as well.
It's important to note that the main determining factor for which "coupling agent" product to use to help solvate the castor is the cost/ounce divided by the treat rate. (without using a solvent)
Here are my thoughts on solutions to help solvate the castor w/o wrecking the viscosity:
1. The use of naphthenic base oils helps some... but not much. Perhaps a couple degrees of improvement before separation occurs. A high viscosity naphthenic base oil with a high sulfur content will help some as well.
2. I'll admit, my knowledge of all the different Ester product offerings is limited... Cargill, Dehylube, Exxon, NYCO, etc all make a VAST array of product offerings. These arent cheap. These products have great film strength and help the solvency some*. I'm sure there are some products that help solvency more than others..im not sure which ones though. Some, (or perhaps all) of these may be cost prohibitive base on their blend mix rate. TMP is the most commonly used product for 2T applications. I need to experiment more with these types of base oils and products.
3. King Industries, Exxon, and a few other companies make AN's. I have no experience with these. They tout better solvency. I know they are used at ~10% in some group III and PAO blends to help solvate other additives. I presume the benzene rings present in the solvents that help solvate the castor oil (as mentioned in my intro,) are serving the same purpose as the benzene rings in an AN. This might be a more attractively priced option if it works well.
4. Another option? comment below. Maybe a Polyalkylene Glycol?
Also,
The use of PIBSA is also an option...but the end use of this oil if for engines that rev to 18,000, and the tack properties of PIB have a known problems of inducing too much heat into the big end conrod bearing. These burn clean, but I dont think are a good use for this particular application...maybe for outboard engines...but not racing engines...I'd highly prefer to not use PIBSA. The ~$20-$25/gallon cost is unattractive as well.
It's important to note that the main determining factor for which "coupling agent" product to use to help solvate the castor is the cost/ounce divided by the treat rate. (without using a solvent)
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