New motor car sales which have been climbing for four straight months from 1,887 in June to 2,559 in August fell to 2,066 units in September, an analysis of motor registry by JB Securities showed.
Sports utility vehicles which rose from 386 units in June to 633 in August fell back to 467 in September.
Three wheeler sales have been hovering around 6,500 units after peaking at 7,369 in July.
Motor cycle sales continued to grow for the fourth straight month, rising from 12,078 in June to 13,855.
Motor car registrations, though down from the earlier two months, were sharply higher from around 1,073 units a year earlier.
Out of 2,066 cars registered in September 71 were brand new.
Maruti/Suzuki continued to be the market leader with 262 registered, with its Alto model leading the pack with 242 units. Registrations were up compared to 112 in September last year.
Registrations of Micro, a car assembled in Sri Lanka with imported parts through a tax arbitrage process, fell to 125 units in September from 229 a year earlier.
Sri Lanka's car sales especially by the less affluent fell sharply after the state jacked up taxes amid a balance of payments crisis.
Analysts have pointed out that balance of payments crises are related to money and credit and are primarily due to excessive money printing by a central bank and trying to curb imports - which is a symptom - is a Mercantilist knee-jerk reaction by authorities.
Sri Lanka jacked up taxes on small cars but gave tax slashed permits to state workers which are being used to import luxury vehicles like the BMW 5-series and Mercedes Benzes.
Registrations of brand new Mercedes Benz vehicles rose to 27 units in September, from 23 in August the highest since March 2013.
Registrations of BMW's rose to 67 in September from 61 in August, down from a peak of 84 in January.
Mini truck (payload below one tonne) registrations were down to 1,360 units in September, from 1,452 units in August but were only slightly lower than 1,482 units a year earlier.
"The mini truck segment is totally dominated by Indian brands – Tata and Mahindra and momentum although slightly down from the highs has not fallen off the cliff," JB Securities said in a research note.
"These products filled a perfect need in the market analogous to trishaws in targeting the middle of the pyramid customers."
Light truck registrations which rose sharply over the past three months to 609 units in August fell to 395 in September, but were still up from 351 in September 2012.
Medium trucks were steady over the past three months with 190 units registered in September, but were down sharply from 298 units a year earlier.
Heavy trucks (payload higher than 5 tonnes) registrations at 107 units in September were also down from 164 a year earlier.
In the first half of 2012 around 700 to 800 trucks were sold a month.
"The heavy truck segment (payload greater than 5 MT) has seen the most dramatic decline which is around 80 percent," JB Securities observed.
"Volumes in this category fuelled by leases (tippers) were at elevated levels – 800 units a month but the demand has fallen off the cliff due to excess supply and repossessed vehicles coming into the market."