Running Engines on Drip

Natural gas comes from two different types of wells. “Wet” natural gas is generally a by-product of oil fields. (Oil wells often alternately produce natural gas and oil.) This is often called “casinghead gas” or “associated gas.” In contrast to wet natural gas, “Dry” natural gas generally comes from dedicated gas wells. Both wet and dry natural gas wells produce a light oil or hydrocarbon condensate that is commonly called “drip oil” or in slang simply “drip.” (Technically, the term drip refers only to the tank (or other vessel) that is used to collect condensed drip oil and other contaminants from low points (the “drip legs”) in natural gas piping, while drip oil is what is collected at the drip. But in common usage, drip oil is often just called “drip”.)

The oil and natural gas companies look at drip oil as a big nuisance. At natural gas fields, the companies typically send tank trucks around on a regular basis to collect the drip oil from umpteen drip tanks. It costs them a lot of money to haul it away. They would much prefer to not have to collect the drip oil quite as often, or at all. Most cars and trucks with standard gas engines can run on drip oil almost as well as they do on gasoline. A mixture of drip oil and gasoline works best. (Since drip oil has a lower octane number and slightly higher volatility than standard gasoline.) It is common knowledge that many natural gas companies intentionally leave their drip tanks unsecured, in the hope that the locals will come and collect the drip oil for them—and they do! In fact, some drip tanks have dispenser hoses and hand lever valves just like you would see at a gas station pump. How convenient.

The major sticking point with drip is that technically, it is illegal for the gas companies to let people come and take it. When people collect drip oil and burn it in their cars or trucks, they are circumventing the federal tax on “road” fuels. So once every few years, the tax “Revenuers” come poking around the major natural gas fields, trying to find out if anyone is running their pickups on drip and cheating on the road tax. Magically—almost overnight–all of the drip tanks get locked up, and the word quickly goes out around the county to stop collecting drip until the federal tax agents leave town. A week or two later, everything reverts back to normal. You just gotta love free enterprise and the American way of doing things.

If you live in an area where drip is available, I’ve heard it suggested storing a couple of hundred gallons of extra high octane aviation gas to mix with drip, to raise its octane level. (A 80% drip/20% aviation gas mixture reportedly will run well in high compression engines.) Another approach is to store a can of tetra-ethyl lead or a similar octane booster. Be warned, however, that these chemicals are highly toxic and special safety precautions must be used for storing and handling them. Just breathing the vapors can be very dangerous! I’ve also heard recommendations to buy a pre-World War II vintage pickup truck with a low compression engine that can run on straight low-octane drip.