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1985 Chevrolet S-10 - spark plug gap

So I went to autozone for spark plugs . They gave me some at a .45 gap. I got home went to change them out and seen that the spark plugs I bought last time are gapped at .6 I took them back and they said they will still work and those r the only ones in stock . Why would there be 2 diffrent gap sizes for my truck?

Unless the world of spark plugs has changed, you gap the plugs yourself to what ever is specified for your vehicle.


They come pre gapped. They gave me .045 and said I wouldn’t have to gap them and that I could just put them right in . But the spark plugs I had were .06

The engine label or owners manual should show which spark plugs are correct for the engine. There are three different engines for that truck, each with a different spark plug.


You have two choices. Put them in and see what happens or return them and have the store order the plugs specified for your engine.

As plugs wear over use the gap may widen.

.45 seems about right for that era GM.

What brand plug are you buying. I recommend AC/Delco since they were the OEM plug for GM back then.

If I just look at the 2.5 liter 4 cylinder… there are plugs listed with gaps from 0.040 to 0.045 but mostly 0.060. The smaller gap will help fire a worn engine better than 0.060 and that may be why they offer it.

The truck also came with a 1.9 liter 4 cylinder and they are ALL gapped at 0.045 but they are NOT the same plug as the 2.5 liter requires. Same for the V6.

Make sure the plug actually is correct by comparing the threads, length and design… seeing as how you didn’t tell US what engine you had, you may have mis-led the parts guy or he screwed up.

That’s assuming the plugs he took out were correct. Who knows?

Check the label under the hood or the owners manual. Use the brand and gap recommended by the carmaker. Anything else is an experiment or a mistake.

The ones I pulled out I measured the gap to .06 .they gave me .045s and after seeing everyone’s response I went ahead and put the .045s in the truck. They run decent. Ima go ahead and order some .06s and see if those are better. The idle issue I had sorta kinda got fixed… but I feel like the .06 would be better . I’ll let y’all know thanks guys

Just re-gap them. Yes all plugs come pre-gapped, but they can still be gapped. I always check the gap before I put them, and many time I’ll find one or two plugs out of gap.