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As a DIY mechanic, it’s easy to get sold on automotive tools. That’s because the industry knows you want to have something in your tool kit for nearly every problem that’s likely to pop up so it tries to push a lot of tools as must-haves. And in the moment, it often sounds like a good idea. But after collecting a bunch of these tools, you start to realize you rarely reach for some of them, which is a shame, because a lot of these specialty tools aren’t cheap.

Sometimes, you already have a tool for the job. Other times, they’re just not as versatile as you expected, and you’d be better off with something more multipurpose. In some cases, these tools just belong in a professional shop and have no business in a home garage. This is why it’s important to know where to splurge when you’re building a tool kit.

So we went searching to see what professional mechanics and enthusiasts have bought, tested, shelved, and eventually cleared out of their tool kits. If any of these are tools you’re considering right now, you may want to think twice about adding them to cart. Because there’s a good chance they’d be a waste of money. If you’re ever in a situation where you actually need some of these tools, your car probably needs to be serviced by a professional mechanic anyway. Ultimately, that’s money you’d be better off putting toward handy tools you’ll actually reach for again and again.

Engine compartments on modern vehicles are tight, crowded spaces, and a standard wrench might not always have the clearance it needs to do its job. Moon wrenches, which are also called half-moon or S-wrenches, were designed with that problem in mind. Their curved shape is meant to reach into awkward angles and confined areas where a straight wrench simply cannot fit. Yet, mechanics hardly find uses for them.

To begin with, moon wrenches struggle to deliver the kind of grip and leverage you actually need when you are working on a fastener. This can be frustrating because it makes you slip frequently while working the wrench. This has led to people finding other ways when they need to reach those tight spaces within an engine. That other way usually involves a bit more disassembly. This means removing the surrounding parts to create the access a regular wrench needs, which takes more time but often proves more reliable.

To be fair, moon wrenches are not useless. In genuinely cramped engine bays, a moon wrench can occasionally speed things up. The key word here, though, is “occasionally.” Some people admit they rarely reach for theirs. If you are building out your toolkit and working with a budget, moon wrenches are the kind of purchase you can skip for now. A good set of torque adapters will serve you far better across a wider range of situations, and a few quality standard wrenches will cover most of what the moon wrench does. Like a lot of tools on this list, the moon wrench is not a bad product. It just rarely earns its place in an everyday DIY toolkit.

Plasma cutters are high-end tools for automotive work. They are used to cut through thick steel and metal, and they reach tight angles that other cutting tools cannot manage. However, unless you do a lot of fabrication work, or you’re planning a full body repair of your car, then this shouldn’t be on your shopping list for several reasons. The first thing that tends to catch people off guard is the setup. Unlike an angle grinder, which you can pick up and get to work with in seconds, a plasma cutter requires a proper power source, an air compressor, hoses, and connections before you even make your first cut. That process takes time, and it is not always intuitive, especially if you are new to the tool.

Then there is the cost. A decent 45-amp plasma cutter will set you back around $800, and that is when you factor in the air compressor and necessary accessories. Step up to a 60-amp unit, and you are looking at $1,000. You can find cheaper options, but mechanics will always warn you that going cheap on a plasma cutter is something most people end up regretting.

Beyond the cost, there is the matter of space. A plasma cutter is not a compact tool you tuck into a drawer when you are done. The machine itself is bulky, and the full setup takes up a meaningful chunk of space in your garage. For a working professional who uses the tool daily, that trade-off makes complete sense. For a weekend DIYer who might reach for it two or three times a year, it is a lot of floor space to dedicate to something that mostly sits idle.

Spark plug testers are tools you can use to test each of your spark plugs to identify which ones are faulty, so you don’t have to replace the whole set. But the thing is, they only tell you whether a spark plug is producing a spark and nothing about the rest of the ignition system. It cannot tell you whether an ignition coil is failing or whether the fuel system is functioning correctly. You can run every plug through the tester, get a clean result on all of them, and still have no real idea why your engine is misfiring.

In contrast, a good OBD-II scanner will point you directly to the cylinder that is misfiring, giving you a far more useful starting point. From there, you can inspect the spark plug yourself and check for corrosion or unusual wear. This way, you can tell if you have a bad spark plug.

There is also the cost point. For most everyday vehicles, particularly four-cylinder engines, a full set of spark plugs is not an expensive purchase. If your car is already approaching the mileage at which you should change your spark plugs, the sensible move is simply to replace the whole set and be done with it. The idea of testing each plug individually to save the cost of one or two replacements starts to look less economical when you factor in the time it takes, and even less so if you are paying a mechanic by the hour. At that point, the labor cost of testing and selectively replacing plugs will almost certainly exceed what it would have cost to replace them all in the first place.

There’s a good chance you have come across an advertisement for a universal socket; they are widely marketed. The pitch is one socket that grips any fastener, any size, any shape, replacing the need for your entire socket set. How they work is that inside the socket, a set of small spring-loaded pins compresses and molds itself around whatever fastener you place it on. In the right conditions, and on smaller, lighter fasteners, it does work. But the gap between what it does in the right conditions and what it is marketed to do is pretty wide.

The first issue is balance. A regular socket sits perfectly on a ratchet and rotates smoothly because it is built for that particular shape. The universal socket, on the other hand, does not always lock onto the exact center of a fastener. The result is a slightly wobbly fit that makes the tool feel jumpy and awkward to turn. Another thing is its lack of grip. The pins find their way around a fastener, but they do not lock on with the same firmness that a solid, purpose-built socket provides. The moment you introduce any real force, the socket can slip around the fastener rather than turning it.

Take the Gator Grip universal socket, for example. It works quite all right on smaller heads, but for larger, tighter bolts that need real torque applied to them, owners complain it simply is not built to absorb that kind of stress. To make matters worse, if you try applying serious force, you risk breaking the tool entirely. Admittedly, this tool has its own use cases. If you’re working on something light like a bicycle, a universal socket might suffice. But this is one tool you’ll never find in a pro mechanic’s garage.

The Texas Twister is one of those tools that attempts to solve a problem you didn’t even know you had. The idea behind it is, rather than buying a dedicated slide hammer, you simply attach this adapter to the air hammer you already own, and it gives you the ability to pull components instead of just pushing them. With one adapter and one existing tool, you suddenly have a pneumatic slide hammer. The problem, according to mechanics, is that it’s not a practical tool.

Out of the box, the kit includes a CV axle popper, a selection of spoons, a hook, and a set of extension bars that are designed to extend your reach into tighter or more awkward spaces. However, those extensions do more harm than good. An air hammer works by delivering a series of rapid impacts in a single direction, and it performs best when that force can travel along a clear path. The moment you introduce extension bars into the setup, that changes. The bars absorb much of the vibration produced by the hammer, reducing the amount of energy available for the work.

Also, the lock nuts that secure the various heads in place have a tendency to back off during use, and this happens regardless of how carefully you tighten them beforehand. Due to a combination of these reasons, this product simply does not produce the pulling force needed to get the job done. If you find yourself needing a similar, capable tool, you might want to consider going for a quality nine-way slide hammer.

The automotive tool industry is a billion-dollar market, with new products coming out almost every week. These tools are constantly advertised as essential, leading many DIY mechanics to believe that the more tools they own, the better technicians they’ll be. We wanted to put together a roundup of tools that the experts themselves have actually bought, used on real repair jobs, and formed honest opinions about. So, we went straight to the source. After scouring YouTube and dedicated automotive forums, we found firsthand testimonies from working technicians and veteran DIYers describing their most redundant tools, and exactly where they did or didn’t deliver.

We also made a deliberate decision to focus on tools you are more likely to recognize. There was little point in building a list around obscure, specialist equipment that only a handful of mechanics would ever come across. Every tool here is something a regular DIYer or home mechanic might consider buying. We looked specifically at consumer forums like Reddit where people have even asked for reviews on some of these tools, so here is an objective look at everything you need to know about whether these tools are actually worth your money.