Q. I just spent 110 days in the hospital recuperating from a serious automobile accident. My company-financed Blue Cross policy, which covers all hospital expenses for 120 days, paid the entire $10,000 hospital bill. But what happens if I have to be hospitalized again soon?

A. Rest relatively easy. Blue Cross does not cancel policies for continued poor health. A spokesman explains that if you leave the hospital and have another accident or contract a different illness, no matter how soon after the first one, you can check back in and start another 120 days, fully paid. If you have to re-enter the hospital with complications arising from the same illness that put you there the first time, that’s another matter. To get an additional 120 days of full coverage, there must be an interval between hospital stays — 90 days under most policies. If you go back sooner, you are covered in full only for whatever portion of the 120 days was unused during your first hospitalization, in your case ten days. After that, unless your policy includes supplementary coverage, you have to pay.

Q. I have heard that if I put radial tires on my car, I will get better gas mileage. Is there anything to this?

A. There is. Because they roll more easily than conventional tires, radials place less strain on the engine. Tests by Firestone Tire & Rubber Co. show that a radial-equipped car driven at a fixed speed between 35 and 50 miles an hour will get about 7% more miles per gallon than a car driven in the same way with conventional tires. But “numbers are misleading,” cautions Kenneth L. Campbell, a Firestone engineer. No one drives at one speed all the time. A typical city driver cruises only about one- third of the time; the remainder is spent idling, accelerating or decelerating. By switching to radials, this driver will see an improvement closer to 2% than to 7% —“such a small number,” Campbell says, “that I can’t advise anybody to buy a tire just based on that.” True, 2% isn’t much; to the average driver it represents a fuel saving of less than 14 gallons a year. But even a 2% fuel saving means less air pollution and could help stave off a predicted gasoline shortage. Fourteen gallons multiplied annually by the 92 million cars in the U.S. is 1,288, 000,000 gallons.

Q. Shortly after my morning flight took off from Indianapolis for Washington, D.C., the pilot announced that bad weather would force a detour. We finally had to land in Philadelphia and take a bus to Washington. I missed all my business appointments, and the trip was nightmarish. Can I get a refund?

A. If you use your ticket, you have to pay for it, says the Civil Aeronautics Board. No airline is rash enough to guarantee its schedules, and the CAB regards inclement weather as an act of God for which the carriers are not responsible. If a flight is more than four hours late, however, the airline must pay for your lodging, meals and transportation to and from the airport. But ask — most airlines do not tell you.

Q. During the past few months I have contributed $100 to national and state political candidates. I understand that a new law will give me a tax break next April. How much of a break, and what are the conditions?

A. The law, passed in 1971, allows political contributions to be treated either as an itemized deduction or as a direct subtraction from taxes. The choice is yours. The limit for a deduction is $50 for an individual and $100 on a joint return. If you prefer a tax credit, you may claim half of your contributions up to a maximum of $12.50 for an individual and $25 for a married couple.

Remember that to satisfy the law, contributions must be made to declared candidates for federal, state or local public office; to a group created solely to promote a candidate’s nomination or election; or to a national, state or local unit of a national political party.

Q. To me, stocks are a long-term investment; I only make one or two trades a year. I know some brokers lost track of their customers’ holdings during the paper-work jam a few years ago. Should I hold my stock certificates myself rather than leave them with my broker?

A. Possibly, because you trade so infrequently. If your broker goes bankrupt, you will bypass red tape by showing proof of stock ownership.

Anyone who buys and sells much more often than you would sacrifice flexibility by hoarding his certificates. If he wanted to make a trade, he would have to take or mail his stock to his broker’s office to transfer ownership. In addition, brokerage houses insure customers’ securities against fire and theft, probably far more comprehensively than your personal policies do.

Q. I make around $20,000 a year, live in a nice neighborhood and have no heavy debts other than a mortgage — but I was recently refused credit because of a bad credit rating. Can I find out why?

Even if you are free of the usual credit demerits — delinquent bills, insufficient salary, youth, too short a time on the job — you may run afoul of others. For example, you may lack citizenship or a telephone. (Bank Americard insists that you have a phone. “If a card is lost, we must be able to contact the person immediately,” says a company official.) Or you may be the victim of some error.

Through the company that refused you credit, find out the name and address of the agency that compiled your dossier. Go to the agency and insist that your file be explained. They must do this, under the provisions of the Fair Credit Reporting Act of 1970. You must be told where the agency got its information, and you can demand a recheck of anything you feel is inaccurate.

Most bureaus will cooperate, according to the Federal Trade Commission. But Robert W. Russell, an FTC lawyer, says some bureaus violate the spirit of the credit law by stalling or insisting on an exorbitant fee to bring out a file. In this case, says Russell, “there’s little a consumer can do other than sue.” Although the FTC will investigate a bureau that has generated a large number of complaints, it does not act on behalf of a lone individual.