Autolite Spark Plug FAQ: Discontinued Numbers, the 65 Cross-Reference, and Black Spark Plug Causes

I'm the guy who kept the mistake file at a local engine shop for nine years. I've personally ordered and installed enough Autolite spark plugs to fill a trunk with bad decisions—wrong gaps, wrong heat range, and a fake B18C1 head gasket scare. This FAQ is the checklist I wish I had. My experience is based on roughly 200 repair and parts orders, mostly Hondas and older Ford inline engines. If you're working on something modern or exotic, your details may differ.

Here's what I'll answer:

• Are Autolite spark plugs discontinued?
• What do people get wrong about the Autolite 65?
• My spark plug is black. Now what?
• Is a B18C1 head gasket really the problem?
• How do I test for a spark plug spark?
• Where can I find discontinued Autolite numbers?
• Autolite spark plugs 65: what gap?
• Can I order just one plug?

1. Are Autolite Spark Plugs Discontinued?

Not the whole brand. But yes, individual part numbers get discontinued—and that stale forum thread telling you to run Autolite 105 is not a reason to panic. I have mixed feelings about Autolite trimming its old copper-core lineup: it makes the catalog cleaner, but it leaves people stuck with an exact number that no longer ships.

A lot of the search traffic about "Autolite spark plugs discontinued" comes from someone trying to match a plug they pulled out of a 30-year-old engine. As of January 2025, the Autolite catalog I check still lists the 65 as a current copper-core plug. Other older numbers have been superseded by iridium or platinum versions with the same reach and heat range.

The practical move is simple. Search the Autolite online catalog by engine model, not the old part number. If you find a supersession, use it. If you find new old stock instead, check the date code and inspect the box before buying. A 20-year-old plug can be fine if it was stored dry, but I wouldn't trust a dented box from an auction bin.

2. What Do People Get Wrong About the Autolite 65?

The Autolite 65 is a copper-core resistor plug that shows up in a lot of older automotive, marine, and small-engine applications. It's a decent everyday plug, not a performance part. The number "65" is Autolite's internal heat-range code, not a universal "colder than 64" indicator.

I've made the mistake of trusting a forum recommendation and running Autolite 65 in a Honda B18C1 because someone swore it was a cheap equivalent. It ran okay for a while, then fouled and misfired. The problem wasn't the plug's quality—it was the wrong heat range and gap for that engine. If you want an Autolite plug for a B18C1, use the application catalog. Don't guess based on the number.

The same goes for the gap. The 65 doesn't have one universal gap. It has whatever gap your engine spec says.

3. My Spark Plug Is Black. What Causes That?

Black. That's the short answer. The longer one: black is either dry soot or wet oily fouling, and they mean different things.

Dry black soot usually means the engine is running rich. Common causes are a dirty or failing oxygen sensor, a bad coolant temperature sensor, leaking injectors, or just a bunch of short trips that never let the engine warm up. Wet black deposits usually mean oil is getting past the valve seals or piston rings.

The plug is a witness, not the criminal.

If you replace a black spark plug without fixing the cause, the new one will look exactly the same in a week.

On one B18C1 I worked on, dry black soot turned out to be a coolant temp sensor that kept the ECU in cold enrichment. There's something satisfying about fixing the sensor and watching the next plug come out tan. Do a fuel trim check and compression test before buying parts.

4. Does a Black Spark Plug Mean a B18C1 Head Gasket Failure?

Usually not. And this is one of those "I paid for this lesson" answers. I once saw a black plug, got tunnel vision, and ordered a B18C1 head gasket kit. Compression and leakdown were fine. The real problem? A leaking valve cover gasket had let oil run down into the plug well. The plug was oily, the head gasket was fine.

A failed B18C1 head gasket can cause coolant loss, white smoke, bubbles in the coolant, or a random misfire. If it leaks coolant into the cylinder, the plug usually comes out looking steam-cleaned or crusty, not black. Black soot isn't the calling card for a head gasket problem.

If you're worried, do a cold compression test, check the oil for coolant, and use a combustion leak tester on the radiator. Those three checks are cheap and take about an hour. They'll tell you more than staring at a plug ever will.

5. How to Test for a Spark Plug Spark Without Getting Zapped

Use a spark tester. You can find them for a few dollars, and they're safer than pulling the boot and grounding the plug against the valve cover. The test is simple: disconnect the plug, connect the tester between the boot and the plug or wire, ground the clip, crank the engine, look for a spark.

You want a bright blue spark that snaps. A weak yellow or orange spark is a spark, but it's probably not enough under compression. Kinda like a candle in a windstorm.

If you have no spark plug spark at all, start with the obvious: clean the grounds, check the ignition coil, the igniter, and the wiring to the crank sensor. A fouled spark plug can also bleed voltage to the shell, so clean or replace a black plug before you blame the whole ignition system.

6. Where Can I Find Discontinued Autolite Spark Plugs?

If a specific Autolite part number has been discontinued, start with Rock Auto, Amazon Warehouse, and local NAPA dealers that still have old stock. You can also call a machine shop that specializes in vintage engines—they often hoard NOS spark plugs.

But before you overpay for old stock, check the current Autolite catalog for a superseding part. In my experience, most discontinued Autolite plugs have a current equivalent with the same thread, reach, taper seat, and heat range. If the modern equivalent costs less and is in stock, buy it. That old box on eBay might be cool, but it's not magic if the plug design has been improved.

One caveat: if you do buy NOS, inspect the boxes for dents and check the date code. I once bought a set of old plugs with a bent ground strap on every single one. Returned them, bought current plugs, never looked back.

7. Autolite Spark Plugs 65: What Gap Should I Set?

For Autolite spark plugs 65, there isn't one universal gap. The gap comes from the engine's ignition system, not the plug. In old Ford applications, I've set them at 0.035 and 0.040. Small engines sometimes call for 0.030. If you don't have the spec, use the Autolite catalog or the service manual for your vehicle.

The bigger lesson: never bend the ground strap by prying it straight from the top. I ruined a set of Autolite spark plugs 65 that way—yanked the electrode, put a hairline crack in the insulator, and didn't realize it until the engine misfired under load. Use a gap gauge and adjust from the side, not the center electrode.

If a forum thread says "just gap it at .044" without telling you what engine, ignore it. Your B18C1 head gasket might be fine, but a gap that's too big can cause a misfire that looks like something serious.

8. Can I Order Just One Autolite Spark Plug?

Yes. I'll sell you one plug. I've been the guy with a $40 single-plug order, and the suppliers who treated that order like real business are the ones I still call when I need $4,000 worth of parts.

Small orders aren't a nuisance; they're potential. If a shop tells you they can't be bothered with one spark plug, that tells you how they'll treat you on the second order. That said, don't expect single-piece pricing to match case pricing. A one-plug order has the same part lookup and shipping cost as a bigger order. That's not a scam, it's reality.

If you're a shop ordering in bulk, the same logic applies. Treat the one-plug customer well today, and you get the whole account tomorrow.