Total new car registrations for the month of August were up 3.5% compared to August last year, according to new figures from the Society of the Irish Motor Industry.
However, in the first 8 months of this year, new car sales were down 3.8% on the same period last year.
In Mayo, 2,091 new cars have been registered between January and August 2018 - that's down by 3.6% year on year.
Roscommon saw a drop of almost 11% in the number of new cars registered in the first 8 months of the year, compared to last year.
Meanwhile, imported used cars have seen an increase of over 10% so far this year, compared to the same period last year.
Director General of the Society of the Irish Motor Industry Alan Nolan says strong growth in used imports will continue to undermine new car sales here.
He says the impact of low sterling exchange rates due to Brexit will have driven used car imports to levels close to the new car sales total by the end of this year.