The new car has disappointed its buyers in many ways, and good mileage is its only ___________.

The blank needs an idiom meaning the only positive quality that redeems something otherwise disappointing.

Option 1 -> saving grace -> means the one redeeming quality that makes up for other flaws.

Option 2 -> saving praise -> not a standard idiom; grammatically incorrect construction.

Option 3 -> saving case -> not a recognized idiom; doesn't fit the context.

Option 4 -> saving face -> means avoiding embarrassment or maintaining dignity, not about redeeming qualities.

When something has many flaws but one good feature that makes it worthwhile, that feature is called a saving grace. It's like having a terrible movie with one amazing actor whose performance makes the whole thing bearable - that actor becomes the film's saving grace.