Behind the door of a 1961 Shasta camper, Karl Poechlauer serves exclusively vegan food.

Poechlauer’s menu takes classic diner food, such as a burger and chicken sandwich, and makes it vegan. But it hasn’t always been that way, said the 40-year-old chef owner, and it probably won’t stay that way.

After an especially tough summer and dramatic drop in business, Poechlauer is considering switching to non-vegan. 

“I see a lot of people come up and they’re like, “Oh it’s vegan? Peace,’” he said. 

For now, the Substance Diner food truck is parked around the corner from Screwbean Brewing at 103 N. Park Ave., serving a menu of vegan diner specials from sandwiches to salads.

Poechlauer didn’t start out serving 100% plant-based food. He started out with a few vegan items on the menu, but as he gained a following, the menu grew.

Poechlauer wanted to simplify the menu and had to do something to narrow it down, so he decided to stick with his vegan items.

 “I thought maybe I could become a vegan brand and gave it a try,” Poechlauer said, although he is not vegan himself. 

Substance Diner has not only diner food, but breakfast as well. The breakfast sandwich and breakfast burrito are both served with an organic tofu scramble, tofu bacon and vegan cheese. The sandwich is topped off with avocado, lettuce and mayo, while the burrito is stuffed with hash browns, pinto beans, avocado and pico de gallo. 

For a sweeter breakfast, Poechlauer has three stack banana pancakes made with organic bananas and almond milk. 

The lunch menu is where you’ll find all the classic diner vegan meals: Spicy Fricken Sandwich, Substance Burger, Barby’s Roast Peace Sandwich, TLT (tamari-tofu ‘bacon’, lettuce, tomato), Kale Caesar Salad, Mushroom Philly Cheezesteak, Fricken Nuggies and a Sonoran Dog. 

Poechlauer buys his bread locally and uses organic vegetables. 

The Sonoran Dog is that one item on the menu that might make someone stop and think, “that’s not what you’d get at a diner.” But this is Tucson. At Substance Diner, the Sonoran Dog is a vegan hot dog topped with organic tomato, pinto beans and pickled onions, drizzled in vegenaise (vegan mayonnaise) and mustard and topped off with tamari-tofu bacun-bits. All of this is stuffed into an organic bun. 

The vegan hot dog, hidden under the assortment of toppings, has the texture of a regular beef dog and beneath the toppings, you might mistake it for a regular hot dog. But make sure to grab some napkins; Poechlauer isn’t shy about overloading the dog with its toppings. 

Originally, Poechlauer wanted to open up a coffee truck. The name Substance Diner comes from coffee, because coffee is a substance, he explained. 

For 2 1/2 years, Substance Diner was located at MotoSonora Brewing, a little over a mile south of Screwbean Brewing. But when he moved to Screwbean, a coffee shop and brewery, the owners wanted him to only sell food. Poechlauer has been permanently parked at Screwbean Brewing since January, and is adjusting to the new demographic of people he is serving. 

That’s not the only thing that’s changed. 

“Times change, markets change,” Poechlauer said, noting that business has been slow.

When business dropped last summer, he had to cut back hours and to let go of former employees. 

He believes that the people he is serving in the new area want something different: something that isn’t vegan. 

Despite a raving 250 reviews on Google, and a 4.8/5 rating on Uber Eats, people don’t seem to want to eat vegan anymore. 

“It was popular, I don’t know if it was like a wave, and now it’s not as popular anymore,” he said. 

Sheryl Lake on Google reviews wrote, “Absolutely to die for! The sandwiches were amazing. I had the Philly cheesesteak- and yes- all vegan! But please know- this food will excite anyone’s palate- you don’t have to be vegan to enjoy these flavorful sandwiches!” 

The review was written five months ago on the Barby’s Roast Peace Sandwich, rating all food, service and atmosphere five out of five. 

Poechlauer thinks people want to eat cheap, especially being so close to the University of Arizona, but serving cheap food means sacrificing the quality. 

“It would be great to get some more attention from the college and get more feedback,” he said. “I’m trying to figure out what [college students] want.” 

Poechlauer will stick with his diner themed food truck, but “a totally new concept might come out of this in the future,” he said. 

Substance Diner is open 4-8 p.m. Mondays-Tuesdays and Thursdays-Fridays; 11 a.m.-8 p.m. Saturdays; and 11 a.m. -7 p.m.  Sundays. It’s closed on Wednesdays. 

Arizona Sonoran News is a news service of the University of Arizona School of Journalism.