Most Americans who heat their homes with oil will have to pay their fuel bills faster this year -- in some cases within 10 days after delivery -- or face penalties in the form of new monthly service charges.

The new penalties will add a few more cents to the price of a gallon of heating oil, which in most cities has already jumped to about 85 cents from roughly 50 cents a year ago.

Since last spring, when the Organization of Petroleum Exporting Countries cut in half the time it gives oil companies to pay for crude, demands for faster payment have trickled down through the oil industry. Now it is the home heating oil customer's turn to pay more promptly.

Steuart Petroleum Co., an independent wholesaler that supplies many Wasington fuel dealers, has notified its customers that oil delivered during the first 15 days of each month must be paid for by the end of the month. Purchases during the last half of the month are due by the 15th of the following month.

Steuart used to give its customers at least 30 days to pay their bills, but demanded more prompt payment after it suppliers did the same, said President Leonard Steuart.

Retail oil dealers are beginning to make similiar demands across the nation, said Allan Darrow, a spokesman for the National Oil Jobbers Council.

In Virginia and a half-dozen other states, heating oil dealers are working on plans to let customers charge their oil purchases on bank credit cards.

That will mean not only interest charges of up to 1.5 percent a month on unpaid oil bills, but also higher fuel prices, the fuel dealers acknowledge. Master Charge and Visa charge retailers a 3 to 5 percent fee on purchases, and dealers say they will have to raise their prices to make up for that.

"We in this industry are in a no-win situation," complained E. A. Catterton, head of the Virginia Petroleum Jobbers Association. "We can't let people go cold and we can't afford to carry them until they can pay their bills."

Record high interest rates are as much to blame as OPEC, the dealers say. The prime interest rate is at 12 percent, and local fuel dealers have to pay more than that to borrow money to buy their oil. Dealers say they already have had to borrow 50 percent more money than they borrowed last year because of higher prices, and now they will have to borrow more so they can pay their bills sooner.

Darrow said the major oil companies have stopped giving their wholesale customers the usual 1 percent discount for paying their bills within 10 days and in some cases want their money within 10 days, with no discount.

Virtually all the big oil companies this year also abandoned their usual "summer fill programs," in which they shipped oil to wholesalers during the summer but allowed them to put off paying for it until the fall.

As a result, local oil dealers have also stopped filling up home fuel tanks during the summer and letting customers defer payment until fall.

Oil company officials blame the Department of Energy and President Carter for that change. (FOOTNOTE)earing heating oil shortages would follow this spring's gasoline crisis, President Carter ordered refiners to build their supplies of the oil up to 240 million barrels by Oct. 1.

Oil industry sources contend the order forced refiners to hold on to heating oil stocks this summer rather than ship the oil to their customers, as they usually do. Energy Department statistics, however, indicate that about the same amount of fuel oil has been shipped from refiners to customers this year as last year.

One impact of dropping the summer fuel program is indisputable, however, -- it enabled oil companies to get higher prices for their heating oil.

Fuel oil prices normally are stable during the summer when demand for the product is low. This summer, however, the price has been creeping up a few pennies each month.

Thus oil that refiners have stockpiled over the summer is worth five or 10 cents a gallon more than it was in June. If that oil had been sold by refiners earlier in the summer, customers would have paid less for it.

Interviews with fuel oil suppliers and trade associations in half a dozen states indicate supplies are good. As Leonard Stuart told his customers, "We are confident of being able to meet our commitments to our customers."

The American Petroleum Institute reported that as of Aug. 17 there were 182 million barrels of heating oil on hand, up 7.6 million barrels from the previous week. At that rate, energy officials say, it should be possible to stockpile 240 million barrels by Oct. 30, a new target date set last week by the administration.

But paying for that oil will be another matter, the fuel oil dealers say.

Many dealers are encouraging their customers to sign up for "budget plans" that spread their oil bills over 10 months.(END FOOT)