Volkswagen’s U.S. sales continue to lag year-ago overall, but a market push behind diesel power appears to have paid off for the brand in March.

Although other automakers are tiptoeing into the diesel market, the sector continues to be a stronghold for Volkswagen, the clear leader among mass-market brands.

Driven by special sales and lease deals, reduced-rate financing and a $1,000 fuel-card incentive, diesels accounted for 26.6% of VW deliveries on 9,764 units in the month, marking the automaker’s best March ever for TDI sales. Through the first quarter, diesels accounted for 21.4% of VW’s mix.

“We really focused in on (diesels) and what we’re really proud of is our unique-selling TDI,” notes Mark Barnes, vice president-sales.

The Passat led the way with its best March ever and highest TDI volume on record. Diesel Passat sales reached 4,549 units, or 41.2% of the model’s mix. Total Passat sales hit 11,050 units, up 20.5% from year-ago.

Overall, VW sales increased just 1.1% on a daily-rate basis (one less selling day than year-ago), despite strong industry sales overall, a pace Barnes expects to continue until new products bolster the lineup and the “next growth phase” gets under way for the brand.

The Jetta proved the biggest bright spot for the automaker in the month, with sales up 8.6% on 15,692 units, despite a 6.0% falloff in Sportwagon volume.

Barnes says VW experienced a “strong resurgence” in demand in the Midwest region in March as weather improved.

“(That) was the slowest region out of the box, because of the weather,” he says. “So there was pent-up demand, and (the market) came on strong. We’re very encouraged by what we’re seeing out of the Midwest.”

There also are signs of general economic growth, Barnes adds, with VW holding to its earlier forecast of 15.8 million to 16.0 million light-vehicle sales in 2014.

This month could see a spike in Beetle sales, as VW says it will announce a sales promotion as early as today for its convertible model to take advantage of the spring selling season.

Separately, the automaker says it is ending its monthly calls with the media to discuss its U.S. sales results. Instead, it now will hold those calls quarterly.

Meanwhile, Audi sales rose 11.6% daily on a volume of 14,246 units, the 39th straight monthly record for the brand in the U.S. Strong Q5 and Q7 CUV demand led the way, but the A6 sedan also posted a solid double-digit gain.

Diesel sales were strong for the Audi brand, as well, accounting for 13.4% of A8 sales, 15.5% of Q5 volume and 25.8% of Q7 deliveries.

“What drove the Audi momentum story to its 39th consecutive record month was consistently strong demand across our product lineup – particularly for our SUV models and our A6 premium sedan,” Audi of America Chief Operating Officer Mark Del Rosso says in a statement. “Add in the tech-forward A3 premium compact sedans after their official sales launch later this week and the outlook for the rest of 2014 is extremely positive.”

dzoia@wardsauto.com