(Adds details of past months, sectoral performance)
OTTAWA, Nov 16 (Reuters) - Canadian manufacturing sales fell unexpectedly by 1.5 percent in September to the lowest level since May, with August's sales also revised downwards, according to Statistics Canada data released on Monday.
The decline in the volume of September's sales was even worse, at 1.6 percent.
Analysts surveyed by Reuters had forecast a 0.1 percent rise in overall sales. August's decline was revised to 0.6 percent from the initially reported 0.2 percent. The combined effect was to wipe out the 1.9 percent increase seen in July, revised from 1.7 percent. The figures are seasonally adjusted.
Statistics Canada blamed September's decline on lower motor vehicle assembly and oil product sales. Motor vehicle assembly sales fell 10.3 percent after four months of gains.
Sales in the oil and coal product sector, which mostly constitute oil products, fell 7.1 percent, the fourth monthly decline. This reflected temporary refinery shutdowns that were more extensive than usual, as well as a 4.0 percent decline in oil product prices.
Reporting by Randall Palmer; Editing by Nick Zieminski