Last month, a federal judge gave preliminary approval to a settlement covering Volkswagen 2.0-liter TDI diesel cars with illegal "defeat device" software.
That settlement included specific amounts VW must pay owners in buybacks.
But just before the public comment period for the settlement ended, Consumer Reports stepped in to advocate for higher buyback amounts.
The magazine said last week that proposed buyback amounts may undervalue the retail prices of certain affected Volkswagen diesel models, according to Reuters.
It called for the use of different values to determine buyback amounts—ones that "would lead to buyback offers for consumers that would be at least several hundred dollars higher."
Consumer Reports also wants owners who opt to have their cars modified to meet emissions standards to retain the right to sell them back to VW if the cars perform differently than they did when sold.
The U.S. Environmental Protection Agency (EPA) and California Air Resources Board (CARB) have not yet approved modifications for the 2.0-liter TDI cars.
Many analysts believe any modifications that may be approved have a strong chance of adversely affecting performance or fuel economy, so giving owners the chance to opt out at a later time offers a fallback for those owners.
Consumer Reports also called on federal and state regulators to "wield robust oversight" of Volkswagen to ensure it complied with all the terms of the settlement.
Under the terms of the preliminary settlement, buyback amounts are based on the "clean trade value" specified by the National Automobile Dealers Association in its Used Car Guide from September 2015, when news of the diesel scandal broke.
Buyback amounts are determined by taking that value, and adding the amount of any payments owners would have been entitled to if they had elected to keep their cars.
Separately, VW will pay owners who agree not to sue the company up to $5,000 each.
Buyback offers will not start until the settlement plan received final approval from U.S. District Court Judge Charles Breyer, which will only come after an October 18 hearing.
Volkswagen must also devise a separate buyback and modification plan for 85,000 TDI models equipped with 3.0-liter V-6 engines.