U.S. light-vehicle sales surpassed expectations in August, claiming their best results of the year on a seasonally adjusted basis.

Volume overall totaled 1.280 million units for a daily rate of 47,421 over the month’s 27 selling days, up 15.3% from year-ago’s DSR of 41,116 on 26 selling days.

August’s 14.5 million-unit seasonally adjusted annual rate marked the highest SAAR since 14.6 million in August 2009, when the government subsidized sales through its cash-for-clunkers program. The result increased 2012’s year-to-date SAAR to 14.2 million, from 14.1 million at the end of July.

Three high-volume manufacturers, Toyota, Honda and Volkswagen (including Audi), get most of the credit for the industry’s large double-digit gain, posting increases of 40.2%, 53.6% and 42.8%, respectively.

Although comparisons with year-ago numbers remain somewhat skewed due to the effect of last year’s tsunami in Japan that temporarily tanked sales for several Asian auto makers, Toyota has run up a string of 10 consecutive increases, including a surge in the past five months that saw gains averaging 45.9% per month.

Toyota’s August market penetration climbed to 14.7% from 12.1% a year ago, and its 8-month share of industry sales reached 14.5% compared with January-August 2011’s 12.7%.

Honda’s comparisons with year-ago also are pumped up due to the tsunami and flooding in Thailand. Nevertheless, its market share in August hit 10.3%, compared with 7.7% in like-2011. Its year-to-date share increased to 9.8% from 9.1% year-ago.

Volkswagen’s August results marked 35 straight year-over-year gains, during which its per-month average increase is 24.1%. Also, its August market share of 4.1% marked the first time since at least 1980 that its penetration reached or surpassed the 4.0% level for three consecutive months. VW’s year-to-date share through August of 3.9% is well above year-ago’s 3.4%, and if maintained, would be the company’s best calendar-year showing since the early 1970s.

Chrysler continued its string of successes, as its 9.8% rise in August was its 29th straight year-over-year increase. However, the gains are starting to narrow as it faces tougher year-ago comparisons. August’s rise was the smallest since a 0.4% uptick in July 2010. In addition, Chrysler’s market share of 11.5% was well below year-ago’s 12.1% and represented the second time in three months its penetration lagged year-ago levels.

Industry leader General Motors posted a 6.0% year-over-year gain, well below the industry average. But its market share rebounded to 18.8% from July’s 17.5%, its second-lowest of the year, and pushed up its calendar 2012 total to 18.2%. However, that result was well below August 2011’s 20.4%, which was the last time GM share topped 20%.

Sales increases at Ford, up 7.8%, and Nissan, up 3.6%, also were noticeably below the industry gain.

Notably, BMW’s August sales fell 9.2%, its biggest decline since a 22.0% drop in October 2009, and only its second downturn in the past 12 months.