For six years, I've signed off on nearly every parts invoice that comes through our maintenance shop. I'm the procurement manager for a 45-vehicle utility contractor fleet, and I track our entire parts and labor spend on a spreadsheet I built in my first month on the job. We spend roughly $180,000 a year in that category—$186,000 last year if you include machine shop invoices. Who's counting? I am. That's the point.
Most of our vehicles are GM gas trucks and vans, so a big share of our purchase orders lead back to ACDelco. Some of that is brand preference. More of it is math. In six years, I've watched cheap parts cost more than the original part would have, and I have the invoice history to prove it.
Before I get to the numbers, let's address the searches that likely brought you here: “location of thermostat,” “crankshaft vs camshaft sensor,” ACDelco TP1015 fuel filter, XG7317 oil filter. Those are valid questions. But after years of tracking every dollar, I think they approach the problem from the wrong end.
A $3.80 Oil Filter Taught Me To Read the Whole Receipt
In my first year, I made the classic rookie mistake: I treated filters as interchangeable. Thread size matched, filter body matched, good enough. So I bought the cheapest case I could find. Everything I'd read about procurement said to minimize unit price. My own experience says price is the smallest number on the receipt. Once a truck is in a bay, labor runs north of $100 an hour here. A tech can install a $4 filter or a $14 filter in the same amount of time. The real difference shows up later.
In 2023, with the quarterly budget tight, I ordered a case of no-name filters at $3.80 each instead of the ACDelco XG7317 oil filter we normally stock for our GM V-8 work trucks. That ACDelco filter runs around $12.50 from our distributor based on our 2024 invoices. Do the math: even on 100 oil changes a year, that's about $870 in apparent savings. It looked like an easy win. Then one of those $3.80 filters leaked from its base gasket on a work truck in the middle of the week. It cost us most of a day, a service call, replacement oil and filter, and credibility with a customer. The $870 “win” was gone before lunch.
No, the engine didn't blow up. The failure was embarrassing rather than catastrophic. But that's exactly the point: low-probability, high-consequence failures do not belong in a procurement policy. The bypass valve spec and anti-drainback valve spec on the ACDelco part are known quantities. The no-name filter was a mystery. I don't buy mysteries anymore.
The Fuel Filter That Almost Became a $900 Mistake
We apply the same logic to fuel filters. One of our older gas 2500s—an early-90s truck we keep for local utility work—came in with low power on a grade. The fuel pump had started getting louder, too. My first read of the invoice history said “fuel pump.” Our senior tech asked a better question: when was the ACDelco TP1015 fuel filter last replaced? The answer was “never, under my watch.”
The ACDelco TP1015 fuel filter isn't a dramatic part. It's a simple inline filter, and it costs less than $20 in our system. But a clogged one makes the fuel pump work against a restriction, which drops fuel pressure and wears out the pump. We installed a fresh TP1015, tested the pressure, and the problem was gone. No pump, no tank drop, no $900 repair event. Just one filter and half an hour of labor.
What I mean is this: on certain older fuel-injected GM trucks, the TP1015 is a maintenance item, not a breakdown item. Treat it like a commodity and you'll learn exactly where it sits in the fuel system—the hard way.
Why We Buy the ACDelco Fuel Pump Flow Control Module
Last year, one of our 2016 2500HDs came in with a no-start. The fuel pump didn't prime. Our diagnostics pointed to the fuel pump flow control module, not the pump itself. If you're used to older trucks—where the pump runs at full speed whenever the key is on—the newer system is a different animal. The powertrain control module sends a fuel pump command, and the ACDelco fuel pump flow control module controls the pump accordingly. When that module fails, it can look like a pump problem, a wiring problem, or an intermittent stall.
My first instinct as a buyer was to find the cheapest module. A supplier offered an equivalent unit at roughly half the price of the ACDelco fuel pump flow control module. I turned it down. Why? Because the module controls the voltage delivered to the pump, and a small difference in that signal creates a hard-to-diagnose fuel pressure problem. I didn't want our shop chasing a phantom code in two months. The ACDelco part cost more. I approved it anyway.
Should mention: we found corrosion in the module connector when we replaced it. Now that connector is on our annual PM inspection list. That's a process gap that would never have shown up if we'd just thrown a cheap part at the symptom.
Searching “Location of Thermostat” Misses the Point
Let's talk about the search terms. Type “location of thermostat” into any search engine and you'll have an answer in seconds. On most GM gas engines, the thermostat is under the housing at the engine end of the upper radiator hose. But I've never once seen the cost problem come from a technician failing to find the thermostat. It comes from installing the wrong thermostat. An aftermarket thermostat can fit perfectly and still open at a different temperature than the engine management system expects. The engine runs cold, the fuel mixture stays rich, and a routine cooling system job turns into an expensive investigation.
“Crankshaft vs camshaft sensor” is the other search that shows up constantly. Both are timing sensors, but they are not interchangeable, and they're not two flavors of the same repair. The crankshaft sensor tells the PCM how fast the crankshaft is turning and where it is in rotation; the camshaft sensor tells the PCM where the valvetrain is in the cycle. Together, they let the engine time fuel and spark correctly. When a truck won't start, the failure pattern tells you which signal is missing. Replacing both to be safe is how a diagnostic becomes an expensive guessing game.
Here's the part that took me years to understand: when you install a replacement sensor or module, you're not just buying a component. You're buying a reference signal. The next diagnostic step depends on trusting that signal. If the signal comes from a no-name part with unknown electrical behavior, the diagnosis starts moving backward. That's why our policy for engine management parts is simple: ACDelco. Not because a logo is pretty, but because the output is predictable.
What was best practice in 2015 doesn't always apply in 2025. The fundamentals haven't changed—engines still need clean fuel, clean oil, and solid timing signals. But the execution has transformed. Newer fuel systems and engine controls demand more precision from every part in the loop.
What the Policy Looks Like Now
Our procurement rule is boring, which is exactly how I like it. Filters, thermostats, sensors, and fuel delivery modules go on the approved list before anyone can place an order. The ACDelco TP1015 fuel filter for the older gas trucks. The ACDelco XG7317 oil filter for our V-8s. The ACDelco fuel pump flow control module for late-model trucks on the same fuel system platform. These are not optional choices. They're standards.
That doesn't mean we never save money. We save on body parts, brackets, lighting, and fasteners—categories where a part failing is an inconvenience, not a breakdown. But when a part controls fuel, oil, temperature, or engine timing, unit price stops being the metric. The metric is whether the vehicle comes back.
After six years and thousands of line items, the conclusion is simple. The cheapest parts are usually the most expensive. I have a spreadsheet full of proof.
