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Pit Stop: Nail Down Your Inventory

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SHOP STATS: At Your Convenience On-Site Service  Location: Jonesborough, Tenn.  Operator: Tim Armstrong  Average Daily Car Count: 10-15  Staff Size: 2  Number of Bays: 1 Ticket Average: $65  

When it comes to inventory, getting started can be a guessing game. Starting as a mobile oil change operation, Tim Armstrong learned very quickly that he had to be smart about what he carried in his inventory. 

Just six months after starting his business, the customer demand gave Armstrong a push to invest in more maintenance services and a physical location. He was taking part in the guessing game once again. Now after 2.5 years, Armstrong has nailed down his inventory numbers, stocking up on only what’s needed. Here’s what he’s learned over the past couple of years on what, and how much of it, to carry in his inventory.

As Told to Abby Patterson


The type of oil you carry depends on where you’re located. The most common types of oils you should always have stocked are 0W-20 and 0W-30 in both conventional and full synthetic. Synthetic oil lasts longer than the conventional kind in the newer cars—about 7,500 miles on average—but you can use it in just about any car, not just the newer ones. 

When it comes to pre-2005 cars, however, there’s a mix of both conventional and synthetic oil used. I carry both kinds of oil because of where I’m located. In the bigger cities and more populated areas, I can imagine quick lubes carry more synthetic oil and some rare grades. If I was in Miami, for example, vehicles with rare oil grades can be common. But there aren’t many of those types of vehicles in this area.

The type of oil you keep in stock also depends on climate and season. For warmer temperatures, you might want to keep some 10W-30 in stock, but up in Minnesota during winter, you’ll want something more like a 5W-30. The lower the W, the more fit for colder temperatures.

One piece of advice I have is to buy a six-gallon tub versus a single quart of the common two grades of oil. It’s more convenient to have and it’s cheaper buying it that way.

Don’t keep rare oils in your inventory. When a customer with a European model comes in with a rare grade of oil, like W-40, I don’t keep it in stock at all times. I only buy what the car calls for and keep it in your customer database. With the help of my database, I get a notification when a customer’s vehicle is due for an oil change, then I give them a call, set up an appointment, and go buy what’s needed for that vehicle. For example, I service a BMW vehicle that requires a 16W-20 grade—I’d never heard of that oil before until that customer contacted me about doing the service. Now, when that customer schedules an oil change, I have to go through the dealership to get it. This vehicle calls for 9.5 quarts of oil, and most Mercedes do, too.

You don’t have to have a wide variety of items. I used to carry headlights and a lot of oil filters. Oil filters, I learned however, are pretty common to one another across the board. When I first started, I carried every kind of oil filter. What I didn’t realize was that it’s more about the number of oil filters you have versus the variety of names; I was carrying about eight to 10 oil filters per vehicle model. Now, I’ve cut back on that inventory by 30 percent, carrying about eight to 10 per make of vehicle, like Honda, Toyota, and Chevy.

AutoZone, which is my supplier, has a restocking program available, so I never have to worry about running low on parts. At the end of each week, I go through my inventory and replenish what I used and get what I need for vehicles I’m servicing the next week.

Your inventory and services you offer depend on your customer base. The customer demand was a big reason for adding on other maintenance services. The most popular product I use with these maintenance services is brakes. Adding brake services is the main reason I invested in my physical. I do some of those jobs on-site through my mobile service, but I mainly do those jobs in the shop.

The types of parts you carry depend on the types of vehicles you service. With a database, you can look back and see that you service about 60 percent Hondas, 20 percent Fords, 20 percent Toyotas, for example. Seeing these types of vehicles, you can see what type of equipment they use and can base your inventory off of that.

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