Autolite FAQ: Copper Spark Plugs, Autolite 64, 2018 Kia Soul Alternator, Honeywell Thermostat & What a Differential Does

I've been handling supply orders for an automotive parts shop for about eight years. Maybe nine, I'd have to check my notes. The point is I've personally made and documented 27 significant ordering mistakes, and roughly $14,000—maybe $12,000—went straight into the mistakes pile. I now maintain our team's parts-ordering checklist. Some of these are DIY questions, but the same lesson applies when I order stamped brackets or CNC-machined mounts in quantity: the part number is the beginning, not the answer.

Autolite Copper Spark Plug: Still Worth Buying?

When I first started, I assumed copper spark plugs were the cheap option and iridium was always the upgrade. That was wrong. Copper has its own strengths: it warms up quickly, resists fouling in certain older engines, and is often the correct material for engines that were designed around it. An Autolite copper spark plug is not a downgrade if the engine spec calls for copper.

The real downside is lifespan. Copper plugs wear faster than iridium in modern engines. If your car came with iridium plugs, switching to copper to save money just means paying labor twice. But if the factory spec says copper, running a more expensive plug in a different heat range can cause misfires. I've seen that Friday-afternoon problem more than once. Copper plugs are also easier to read during a tune-up, since the electrode color can tell you if the engine is running lean or rich. That's a real advantage for someone who actually diagnoses engines instead of throwing parts at them.

Autolite Spark Plugs 64: What Am I Actually Buying?

Autolite Spark Plugs 64 is a search phrase I get from customers who already know the number but not always the spec. According to Autolite's published catalog, the 64 is a copper-core plug. The number is a model code, not a magic fit-any-engine code. It's popular with older Ford-family engines, but the actual gap and reach still need to match the engine in front of you.

In my early years, I bought a batch of these based on a customer's word that the old plug had '64' on it. It was an older Ford engine, so the number seemed safe. The problem was the gap. I didn't check the spec, the plugs were gapped for one application, and the engine idled rough. That mistake cost a few hours and a very unprofessional voice message. What I mean is: the part number gets you close, but the service manual tells you final. Check both before you order 200 of anything.

2018 Kia Soul Alternator: Do I Need to Pull the Front End Apart?

No, you don't need to pull the radiator or move the A/C compressor. According to Kia's published service information, the 2018 Kia Soul alternator is mounted high enough that you can reach it by removing the intake duct and loosening the drive belt tensioner. I learned this after spending an embarrassing amount of time trying to find a bolt that I'd already reached past.

The bigger trap is ordering the right alternator for the engine. The 1.6L and 2.0L Souls do not use the same unit in my experience. I'm not 100% sure about every late-year factory variant, so I always check the VIN before quoting. The mounting bracket is often a stamped steel part, and it can look identical while having a different hole pattern. Measure the bracket, don't trust the photo. And disconnect the negative battery cable before touching the B+ nut. I shouldn't need to say this, but I have seen the sparks.

What Does a Car Differential Do?

A differential lets the left and right wheels rotate at different speeds while still receiving power. When you turn, the outside wheel has a longer distance to cover than the inside wheel. Without a differential, that speed difference would fight itself—tires would hop, scrub, or bind through corners.

For a long time, I thought differentials were only in rear-wheel-drive trucks. Then a customer asked me about a transaxle on a front-wheel-drive van, and I had to admit the differential is built into many front-wheel-drive transmissions too. An open differential is different from a limited-slip or locking differential. Most everyday cars have an open differential, which is why one wheel can spin on ice. That was another thing I didn't understand until I saw it explained on a lift. The symptoms of a worn differential—whining, clunking, or a vibration that changes on corners—are easy to blame on tires. On front-wheel-drive cars, the differential shares the transaxle fluid, so low or old fluid can make the same noise. I've seen a customer spend hundreds on tires before anyone checked the fluid level. Start with the simple thing before you condemn the part.

What About the 'Honewell Thermostat' Search?

I have to be honest about my limits here. A lot of people land on this page after typing 'honewell thermostat'—usually without the y. If you want a home thermostat, you are in the wrong garage. If you want an automotive thermostat, I still won't pretend a Honeywell thermostat belongs in every car. Honeywell's consumer auto parts group once included Autolite, but that business was separated years ago. I only know this because a customer asked me in 2020 and I had to look it up.

For a 2018 Kia Soul, the coolant thermostat depends on the engine code, not the brand. I don't carry thermostats in my normal line, so my move is to give you the OE part number and point you to a supplier who lives in that lane. If you're asking because you remember the Honeywell name on an old Autolite box, I get it. Brand histories are messy. But ordering a thermostat because you remember a brand is the same mistake as ordering a spark plug because the number looks familiar. A vendor who says 'this isn't my specialty, but here's who does it' is more trustworthy than one who says 'yes, I do everything' and then charges you for the learning curve.

What's the Real Lesson Behind All of These?

Every mistake I've made in the last eight years comes back to the same thing: I trusted the label more than the spec. An Autolite copper spark plug, a 2018 Kia Soul alternator, a differential, a thermostat—they all have one thing in common. If the car says one thing and the part box says something else, the car wins every time. My experience is based on maybe a few thousand orders with engine parts and stamped components. If you work with a different class of vehicle, your details might differ. But the rule is still the same: the part number is a language, and the car speaks it fluently. I've just learned to listen before I order.