Sales of medium- and heavy-duty trucks in the U.S. rose a whopping 62.8% in October, the biggest monthly increase of the year, WardsAuto data shows.

The jump largely is due to a 107.6% spike in Class 8 deliveries, a segment in which nearly every manufacturer finished the month sharply above year-ago.

Related document: WardsAuto U.S. Truck Sales by Weight and Class – October 2011

International, up 184.8%, was the leading gainer, although its sales total was surpassed by Daimler and PACCAR, whose deliveries jumped 87.1% and 109.9%, respectively.

Daimler’s Western Star brand was the poorest Class 8 performer. Its sales rose 42.4%.

Deliveries of medium-duty trucks rose 23% in October, with only Class 7 falling behind year-ago on a daily sales basis.

Largely due to International’s 20.6% shortfall, Class 7 sales fell 4.2% in October. Deliveries of imported units rose 25.5%, reflected in the 33.5% jump in sales by UD Trucks.

PACCAR’s Peterbilt recorded the most prodigious increase in Class 7, up 101.0% year over year.

Class 6 had the second-best performance of all medium or heavy groups, with sales climbing 59.7%. Three brands in the segment – Daimler’s Freightliner, Hino and International – notched triple-digit year-over-year spikes, on a percentage basis. Hino’s 138.0% gain was the largest.

Daimler’s Mitsubishi Fuso model saw the largest drop in Class 6, down 84.6% on just four units sold last month.

Class 5 sales rose 28.4%, with most manufacturers recording increases from year-ago. Mitsubishi Fuso was superlative, posting a 140.1% increase.

In stark contrast to its Class 6 performance, Hino sales slumped 88.5%, with just one unit delivered.

Class 4 sales rose 32.4% year-on-year with good performances by the segment’s remaining players.

Freightliner deliveries skyrocketed 580.0% on 203 deliveries, up from 31 units year-ago.

Ford’s 45 units dropped the manufacturer 73.3% below like-2010’s 175 deliveries.

Through October, medium- and heavy-duty sales were running 39.5% ahead of prior-year’s 246,203 deliveries to 176,530.

Class 8 days’ supply declined to 49 days from 68 as October came to a close, but stocks rose to 32,648 units from 22,032 year-ago.

Medium-duty days’ supply and inventory both saw increases to 74 days and 33,268 units, respectively, compared with year-ago’s 70 days and 25,387 units.