Many years ago (20?) Consumer Reports decided to check into car
batteries. They entered the study with the preconceived expectation
that all car batteries would be the same, and were planning on coming
up with evidence to support their idea that you should just buy the
cheapest battery, without regard to brand.

But they got surprised. They found clear evidence that different
brands and makes were different. And that warranty support was
extremely good for some.

They came out recommending Interstate brand (among others), noting
that the batteries were among the best in quality and their
widespread availability made warranty replacement easy.

Things change over time, and what was true in the past may not be
true now. However, I've never been disappointed with Interstate
honoring their warranty. I've got MTP-91's in several of my Vanagons.
And prefer to go out of my way to get them.