Howdy Back PB:
I musta missed this post last week. Anyway, What I know is that all manufacture use their own rating scale. Most product books have a cross over chart for the major brands.
I'm particularly partial to Champion because of their historic connection with Smokey Yunick. He experimented and pattened the extended reach spark plug, which has become a standard in the plug industry. Other manufaturer have there own name for the feature and are not always true to patten rights.
My current summer heat range plug is a Champion RF14YC. The "R" stands for "Resistor", which cut down on radio interference. Again a standard of the industry. The "F" refers to the reach of the threads and the diameter of the spark plug hole. The number is the heat range. Champion uses three different number ranges; 1 - 25 for automotive, 26 - 50 for aviation, and 51 and up for racing, competition and other special uses.
The "Y" indicates the type of nose or reach of the electrode. In this case, a projected nose. The letters of the retracted and regular nose escapes me at the moment. THe "C" refers to the "Cooper Plus" design.
The heat range number with Champion is easy to figure- The higher the number the hotter the range of the plug. The exceptions is that racing plugs have a higher number but all are colder then production plugs. Once you get into racing numbers the lower the number the colder the plug. Racing plugs are harder to find and more expensive. I usually use RF18YC for winter.
The contrast is that a hotter plug is better for low speed, easier start and warm up, rich choke and cold oil conditions. also for older engines that are prone to use a little oil. A colder plug is better at high rpm, higher temperature and compression and WOT. And for leaner, cleaner running engines. Cold plugs used in cold weather or low speeds will foul and darken quicker. Hot plugs used in power applications will be prone to high speed misses and less peak power. Also more prone to pre-ignition.
So what's the best heat range? In a stock engine the factory recommended plug is going to be very close to right. In a modified engine only trial and error can determine the right heat range, but in general start your search for the perfect spark plug with a plug one to two steps colder than stock.
I'm with you on the high dollar, gimmicky plugs on the market today. However I do use them in my wife's Lincoln LS and in my high mileage van. These engines are lucky to see new plugs every 10,000 miles. I check the Falcons plugs at least twice a year. More often if I'm tuning.
I hope that helps your query.
Adios, David
