jhov,
The Commonwealth EDM-244 is an excellent fluid, but I HIGHLY RECOMMEND moving up to a full synthetic fluid such as Commonwealth SuperSupreme. Any conventional mineral-based EDM fluid (such as 244) will have a limited and specific useful lifespan. Think of conventional EDM fluid like a Gallon of Milk...while Milk is still Milk after its expiration date, the operator/user experience with spoiled Milk can be horrible!
To make the connection...conventional EDM fluids will degrade and change their di-electric characteristics over time, and this fluid breakdown and spoilage (like Milk) will occur in time regardless to how often the machine is used. As conventional EDM fluids age, the machining stability degrades as a result of the fluid no longer acting like a proper insulator for the EDM process. This fluid breakdown results in degradation of machining accuracy, rougher surface finish and/or surface imperfections, and longer cycle times. Unlike Wine, conventional EDM fluids DO NOT age gracefully with time...they often darken in color, create a distinct and not so nice odor, and can cause operator skin issues and irritation....all BAD things! I have personally seen severely aged EDM fluid contribute to increases of cycle times in the range of x3 to x4 time longer! To put this a different way, what do you think the performance and efficiency of your car or truck would be with oil that has 100,000 miles on it?
A key benefit of switching to a full synthetic EDM fluid is that these fluids do not breakdown or lose their di-electric strength properties over time. In most cases, a full synthetic EDM fluid should be considered a one-time purchase, as the fluid does not need to be replaced long term. You will pay a 20~30% Price Premium to upgrade to a full synthetic EDM fluid over conventional mineral-based oils, but you will realize a long-term savings benefit of eliminating the need to replace the fluid, realize consistent machining performance, and most importantly provide greater health safety to the operator.
-Brian