You like to keep your peanut butter in the fridge. Your spouse says it’s fine on the shelf. Who’s right? Actually, you both are, as long as you plan to finish the jar within a few months. Put an end to the “Great Condiment Debate” with this handy list of storage and shelf life tips for your favorite dressings and spreads:

Ketchup Like many condiments, ketchup can be stored either in the refrigerator or on the shelf even after it’s been opened. If you don’t use it regularly, however, opt for the fridge. Unopened ketchup will last at least a year. Once opened, it should be used within a month if stored in the cabinet or within six months if stored in the refrigerator.

Mayonnaise Unopened mayonnaise stored in the pantry should ideally be used by the “Best By” date on the package (but in most cases will still be good for up to four months after that date). Mayo is made from eggs, so it must be refrigerated once it’s been opened. A jar will last up to three months in the refrigerator and should never be left on the counter for more than an hour or two.

Read more: Ending the Great Condiment Debate

The most popular theory is that the word ketchup was derived from “koe-chiap” or “ke-tsiap” in the Amoy dialect of China, where it meant the brine of pickled fish or shellfish. Some people prefer the Malayan word “kechap” (spelled ketjap by the Dutch), which may have come from the Chinese in the first place.

Read more here: The condiment “KETCHUP” where did the name come from?

For decades there was only one way to use the humble ketchup packet, and it was messy. Now, fast-food lovers have a choice: the traditional squeeze play – or the option to dunk.

You want fries with that, in the minivan? No problem.

The new ketchup pack, unveiled Thursday by H.J. Heinz Co., is shaped like a shallow cup. The top can be peeled back for dipping, or the end can be torn off for squeezing. It holds three times as much ketchup as a traditional packet.

Customers at a McDonald’s in Covington, Ky., said they would welcome a redesign.

“You use up a lot of ketchup now with the packets, I always get extra ones,” said Skyler McDermott, 29. “Maybe now you won’t have to use your teeth to open them.”

Heinz struggled for years to develop a container that lets diners dip or squeeze, and to produce it at a cost acceptable to its restaurant customers.

“The packet has long been the bane of our consumers,” said Dave Ciesinski, vice-president of Heinz Ketchup. “The biggest complaint is there is no way to dip and eat it on-the-go.”

Designers found that what worked at a table didn’t work where many people use ketchup packets: in the car. So two years ago, Heinz bought a used minivan for the design team members so they could give their ideas a real road test.

The team studied what each passenger needed. The driver wanted something that could sit on the armrest. Passengers wanted the choice of squeezing or dunking. Moms everywhere wanted a packet that held enough ketchup for the meal and didn’t squirt onto clothes so easily.

Heinz is rolling out the new packs this fall at select fast-food restaurants nationwide. It will continue to sell the traditional packets.

Whether restaurants buy the new packets will depend on cost, experts say.

“One of the top uses of ketchup in this country is on french fries,” said Harry Balzer, vice-president of the research firm NPD Group. “One of the patterns of behaviour in this difficult climate that continues to do OK is ordering and eating in your car.”

The company said it is still working out prices with its customers. But the new packet should cost only a little more, even though it holds much more ketchup.

Heinz is by far the biggest ketchup maker. About half of its ketchup is sold in stores and the other half is sold to the food service industry through its exclusive contracts with chains like Burger King and Wendy’s.

McDonald’s, the nation’s largest burger chain, does only limited business with Heinz.

Heinz sells more than 11 billion ketchup packets every year. But neither the ketchup maker nor the major chains would say who plans to carry the new design.

Morningstar restaurant analyst R.J. Hottovy said if restaurants do adopt the design, the transition will likely be gradual.

“It has to be proven that this is something that saves money on the behalf of restaurants or cuts down on waste,” he said. “It looks interesting, but ultimately you have to provide something of value to the restaurants.”

Customers may force the issue.

Rants about the messy packs have helped spawn hundreds of anti-ketchup-packet groups on Facebook.

Matt Kurtz, a 22-year-old student in New York, has drawn 269 members to the group he started after he ripped open a packet too quickly and spilled it on his jeans while on a road trip two years ago.

“That’s when I said ‘There has to be a better way.”‘

These issues come as no surprise to Heinz’s Ciesinski. “We created the packet in 1968,” he said. “Consumer complaints started around 1969.”