Poverty vow or no, Quantico's preaching Marine major delivers the "Good Word" in a Mercedes-Benz.

Maj. Jeffrey Zorn, who lost his job as a military aide to President Carter in April as a result of an Internal Revenue Service investigation into his personal finances and those of a church he founded, bought the used car in 1978 and gave it to his church. It was valued at $11,000 at the time.

The car is one of two diesel Mercedes Zorn has acquired for his Third Estate Church since he took a vow of poverty and became the church's pastor in 1976.

The church, which has since traded one of the cars, allowed Zorn to commute to Washington in one while he worked at the White House because, in Zorn's words, it presented him with "a divine opportunity" to spread the gospel.

Zorn, who so far has succeeded in denying the IRS access to church records, describes the church's ownership of the expensive German imports as "good stewardship," designed to save money in fuel and maintenance.

"We knew in 1978 that gas prices were going to go up to $1 a gallon," he said. "And we looked at a lot of cars. But we couldn't find any American cars that met our requirements."

Indeed, a dealer at American Service Center in Arlington, where Zorn bought a Mercedes Benz 240-D two years ago, said: "It's an economical car, there's no doubt about it. It gets 30 miles to a gallon and it doesn't depreciate much."

Zorn said he gave two cars, a 1973 Corvette and a 1974 Cougar, to the church when he took his a vow of poverty. The sale of these, he said, helped allow for the purchase of the Mercedes. The church has since sold one Mercedes and bought a Volkswagen Diesel Rabbit as well, the officer said.

A decorated Marine Corps veteran, Zorn says he spends his free time as a born-again evangelical pastor of his 12-member church and travels "up and down the East Coast" to find converts.

Church members meet in Zorn's house on the Quantico Marine base, but he also teaches Bible classes to residents of local nursing homes. He said it was difficult for older followers to get into the smaller American cars.

Besides, said Zorn, a nearby Baptist minister travels the Prince William County roads in four-wheel luxury. "He has two Mercedes," Zorn said.

Zorn was transferred from the White House in April, two days before his six-month "fitness report" was scheduled to go to Carter for the president's signature. Zorn, who is now assigned to a Quantico desk job, said the fitness report still has not been approved.