One family. One garage. Thirty-eight years.

Westside Auto Service has been on the corner of Mississippi and Federal since 1987. We are not a chain. We are not a franchise. We are a family — a father, a son, a daughter-in-law, and five technicians who have been wrenching on European cars long enough to know what a B8.5 Audi sounds like when the timing chain tensioner is about to fail.

The FoundingKarl, 1987.

Karl Brennan started Westside Auto Service in 1987 with a $4,000 loan from his father-in-law and a single rented bay on Mississippi Avenue. He was thirty-eight years old. He had spent twenty years at the Volkswagen dealership in Boulder — first as an apprentice, then as a journeyman, then as the lead European-car tech the dealer service writers brought every problem they couldn't solve.

Karl had grown tired of two things: the service-writer system that pushed technicians to upsell, and the parts-only-from-the-dealer-warehouse rule that made repairs cost more than they needed to. He'd seen too many customers walk in with a $400 problem and walk out with a $2,200 bill. So he left.

His first customer at Westside was a 1979 Audi 5000 with a stuck rear differential. The car had been to two shops already. Karl pulled the diff cover off, found a snapped pinion bearing retainer, sourced the part from a used-car wrecker in Wheat Ridge, and had the car back on the road by Thursday afternoon for $340 — about a third of what the dealer had quoted. He still has the handwritten work order pinned to the bulletin board above the parts counter.

By 1991 Westside had expanded from one bay to three, hired its first additional technician, and earned its AAA Approved Auto Repair designation — which it has held continuously ever since.

Before WestsideThe Boulder VW years, 1965–1987.

Karl started at the Boulder Volkswagen dealership in 1965 as an apprentice — sweeping floors, sorting parts, watching the journeymen. By 1968 he was on the floor. In 1972 the dealer sent him to the Volkswagen factory training program in Wolfsburg, Germany, where he spent six weeks pulling apart and rebuilding Type 1 and Type 4 engines under the supervision of VW master technicians.

That Wolfsburg trip is the line Mark draws between his father and every other independent mechanic on the West Side. "Dad came back from Germany and was the only guy in Colorado who'd been trained by the people who actually built the cars," Mark says. "He spent the next fifteen years at the Boulder shop watching European cars come in that the service writers couldn't make sense of. He'd diagnose them in twenty minutes. That's the foundation everything here is built on."

The Second GenerationMark, 2014.

Mark Brennan grew up in the shop. His earliest memory is sitting on top of a 1984 Audi 4000 quattro engine block in the parts room while Karl explained what each component did. He was four years old. At sixteen he was sweeping the bay floors after school and handing tools to the techs. At nineteen he took the ASE A1 exam and passed. At twenty-seven he held all eight ASE certifications and the Master designation.

Mark took over the day-to-day in 2014 when Karl turned sixty-five and decided he wanted to spend Wednesdays on his BMW R69S motorcycle instead of under cars. Karl still drops by every Wednesday morning, mostly to argue about the espresso machine and tell Tony Rivera he's torquing things wrong. Mark says the arguments are good for the shop's culture. Tony, off the record, says they are not.

Under Mark, Westside has invested in factory diagnostic equipment for every European make: VAG-COM for VW and Audi, BMW ISTA, Mercedes XENTRY, Porsche PIWIS, Volvo VIDA. The shop is a Bosch Service Network member, a NAPA AutoCare Center, and a Colorado licensed inspection station. The bay count has grown from three to six. The technician count from two to five.

The Front OfficeLisa, 2018.

Lisa Brennan joined Westside in 2018, six months after she and Mark got married. She had spent twelve years in customer-experience roles at a regional credit union, then a year as the service-counter lead at a Colorado Honda dealership. The Honda job is where she learned what the service-writer game does to customers — and why she didn't want to do it.

Today Lisa runs the appointment book, the customer communication, and the parts ordering. She is the reason Westside answers the phone within two rings. She is the person who calls you with the diagnosis and the estimate before the work begins. She is the reason every customer leaves with a clear understanding of what was done, what wasn't, and what is due next. She holds the Bosch Service Advisor certification and the NAPA AutoCare Service Manager certification.

Karl told me when I took over: "Don't sell anyone anything they don't need. Show them the part. Charge them fair. They'll come back for thirty years." He was right. — Mark Brennan

TodayThe shop in 2026.

Westside today has six service bays, five ASE-certified technicians (four of them ASE Master-level), and Lisa at the front. We're affiliated with AAA, ASE, Bosch, NAPA, and the Colorado emissions program. We have 487 Google reviews and a 4.9-star average. We have roughly 3,200 customers on our active service-reminder list. We've serviced more than 28,000 individual cars since 1987 — every one of them logged in the same yellow-spine paper service binders Karl started keeping in his first year, plus a modern shop-management system that Mark added in 2015.

We work primarily on Audi, BMW, Mercedes-Benz, Volkswagen, Porsche, Mini, and Volvo. We do not turn away other makes — if you bring us your Honda or your Toyota, we will service it competently. But the European platforms are our specialty, the cars we know best, the cars we have parts relationships for, and the cars we have factory diagnostic equipment for.

That's the story. If you'd like the rest of it told over coffee, walk in any Wednesday morning between 7:30 and 9:00. Karl is usually around. He'll talk your ear off about Wolfsburg.