Going to 134 actually will result in less overall system capacity. R12 is not cheap. If you have system with slow leak that needs to be topped off it can become costly. Going to hc12a is cheaper has better performance uses same components and requires no oil change and is considered environmentally friendly I have used hc12a with very good success. But what way is cheaper? If done right, after initial conversion 134a cheaper. But hc12a is easy and cheap. Long live the s12!