How would you like to have your own gasoline supply right in your garage or backyard?

You wouldn't have to worry about a shortage and future long lines at the pumps. While others were waiting at filling stations, you could just "fillerup" whenever necessary.

A dream? Not really. Of course you can't have a gasoline tank in your garage or backyard because it's too dangerous. Many communities have banned the installation of gasoline tanks because, without proper venting and insulation, a spark could set off the whole neighborhood.

But in most communities nobody says anything against having a diesel fuel tank in your yard, your garage or your basement. Why? Because diesel fuel is, in most instances, identical to heating oil. And there are millions of heating oil tanks around homes all across the country.

In many areas you can call up, have a heating oil tank installed (275 gallons is the average, but you can get bigger), and use the stuff in your diesel-motored car or truck. The major oil companies such as Exxon, Texaco, Shell and Gulf make number 2 diesel fuel the same as number 2 heating oil. They do this because the oil is easier to distribute and market if it can go in a furnace or an engine.

But, wouldn't you know, there's one great big problem. Putting heating oil in your car or truck is illegal. When you use oil designated for heating, you're not paying a "road tax" imposed on diesel fuel by the various states and the federal government. Most states tax diesel fuel at around 9 cents a gallon and the federal government tax is 4 cents a gallon.

After the big gasoline station crunch in the spring and early summer, some people who owned diesel cars and trucks caught on to the idea that you can interchange heating oil with diesel fuel.

People who already were using heating oil just opened a spigot on the side of their tank or, in a number of cases, ordered a new tank to be installed right next to the old one.

Some motorists who weren't using heating oil called heating oil dealers and had tanks installed anyway. As one dealer said: "It's not our job to inspect the home to see if there's an oil furnace inside."

Installation of a 275-gallon oil tank costs around $200 to $250. There's no need for special insulation or venting as there is in a gasoline tank and this saves a lot of money. Also, diesel car and truck owners can carry around five-gallon tanks without much, if any, danger of explosion. Portable gasoline tanks are like bombs ready to go off.

But what about that pesky road tax? A number of states are getting wise to the backyard filling station syndrome and are cracking down on violators. Lowry Brooks, chief auditor for the Maryland Gasoline Tax Division, says "collections on back taxes for heating oil used in cars and trucks are up considerably this summer."

Brooks and his tax enforcement officers have car and truck dealers lined up to supply the names and addresses of every diesel buyer. These names are then matched with others provided by heating oil dealers and tank installers.

When a new diesel is purchased and the buyer starts getting more heating oil, or gets heating oil for the first time, then an inspector pays a visit. If the buyer can't show receipts or credit card statements to back up all the fuel for the mileage on the vehicle, a bill for back taxes is issued. Other states are charging fines of up to $5,000 and imposing jail terms of one to three years for fraudulent misuse of heating oil. If you state you need the oil for heating and don't even have an oil furnace, you could be charged with fraud. But most states say you can pay the tax regularly and have your backyard supply. You have the convenience and security -- they have their tax money.

Q: Is it possible to get a tax credit or deduction for the installation of energy-saving reflective film on windows? Also, do you get credit for installing a new furnace or air conditioner that saves energy?

A. Sorry, Internal Revenue Service officials say you don't get the tax credit for energy-saving with the installation of reflective window materials or a new furnace and air conditioner. You don't get any credit for the installation of fluorescent lighting, a microwave oven, a wood-burning stove or a heat pump even though these items do save energy.

You do get credit for the installation of storm windows, insulation and solar or wind energy generators. You also get credit for the purchase of an automatic "set-back" thermostat, electronic ignition device for gas furnaces, modification of furnace flue openings, energy-saving replacement burners for furnaces and replacement of a gas (or electric) meter that shows the cost of energy, not just the amount.