American Security Bank has lowered the down payment on its new-car loans to 10 per cent. With the average sticker price of a new automobile around $5.900 this year, it means a buyer would put down between $590 and $885 less than currently required by other Washington area banks.

In addition, American Security has reduced rate on 42-month loans to 9 per cent. Only one other bank of 13 surveyed last week and yesterday. Riggs, offers a comparable interest rate for that length loan, although it requires a 25 per cent down payment.American Security's rate remains 10 per cent for a 48-month loan and 9 per cent for a 36-month loan.

J. Timothy Holland, senior vice president said the multi-feature package is designed to appeal to a variety of customers. "We are simply demonstrating that we want their business and we will design our products to fit their needs," Holland said.

Last April the bank held an eight-day Saturday Loan Sale, offering consumer loans to 9 per cent. A bank officer said American Security did three times its normal loan volume in that period. Unlike that event, there is no time limit on the 10-per-cent-down auto loan offer.

The 10 per cent requirement refers to the suggested retail price before dealer discount and trade-in are considered. For example, were the sticker price of a new car $5,000 and the discount amounted to $500, no down payment would be required. In effect, the bank would finance 100 per cent of the purchase price.

National Savings & Turst Co. comes closet to American Security in its down payment, although its interest rates range from 9.5 per cent for 36 months to 10.25 per cent for 48 months. NS&-T requires down payments of from 11 to 25 per cent depending on the dealer's price. Where the dealer's mark-up on a small import is 11 per cent, that is the size of the down payment. This ranges up to a 25 per cent down payment on a luxury car.

Several area banks charge lower interest rates than American Security, but their down payments are higher. Union first, for example, charges 8.75 per cent for 36-months loans for more than $5,000. First Virginia charges 8.86 per cent for a 36-month loan of any amount.

Should automobile fanciers not find financial satisfaction at American Security, they always can try Maryland National. While the hoi polloi make do with 10.5 per cent loans for 48 months, antique car buffs can get loans for 60 months. It also pays to be a good customer. A physican recently got 100 per cent financing for his $75,000 Rolls-Royce.