A. Torah Lishmo (40) and Tzitz Eliezer (12: 17) both write that the main Schar Pesios is when one exerts, puts effort and work in the compliance of the mitzvah. That is comparably minimal when one travels by car. They suggest, time permitting, to park the car a bit far. Betzel Hachochmo (4: 21, 5: 101) mentions that although traveling by car involves certain monetary expenditure, the bodily effort is more important and advises that from time to time, one should do the effort to walk to shul.
Horav Shlomo Miller's Shlit"a opinion is similar
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit"a
Important Numbers
