West coast Canada, 1960s-2000s, parents from the Prairies and Nova Scotia, and it was deckle all the way through family lines and timelines. Decal rhymes with heckle, which is what we would do to precious and pretentious, or worse, US “Dee-cal” types.
Seems to be also in Australia. And the Cambridge (UK) dictionary doesn’t give the “deckle” variant, either, but seems to imply the word itself is more used in North America.
https://en.wiktionary.org/wiki/decal
That says “deckle” is more a Western Canadian pronunciation, as well.
Which should be taken as definitive, of course.
It’s standard pronunciation in the East, too. And it’s not really “deckle”, because the “a” is voiced, hence “DECK-al”.
Note my careful use of the word “seems,” and pronunciations that are standard in one area of the English speaking world may not be elsewhere. It’s interesting to me where the pronunciation is common, as I love local dialect and accents, and the specificity of Westen Canada I find is also interesting if correct.
Then that pronunciation is a little bit different than what is being described. The pronunciation in the OP’s link and there’s one on forvo.com under “other” is “deckle.”
No, no, my point is that western Canada pronunciations, more particularly the ones I learned as a youth, are to be considered definitive! Everyone else is just wrong.
It’s dee-kal, also,
Now, now, we can’t be too harsh. The western Canada pronunciation is of course superior.
But « wrong » is a bit strong. I think the alternatives should be labelled as « regional dialects ».
I fear our neighbours will mistake our politeness for weakness, and so we must labour to make our true colours known, eh?
Well, youse people is just weird.
Another SoCal native, and I’ve always said dee-cal. I have never even heard of the deckle variation, let alone heard it spoken. I hear ‘deckle,’ and I think of the edges of the pages in old timey books.
no, feckle. What you had before you were feckless.
We is weird because we pronounce words correctly and spell them correctly, too? 
Incidentally, true fact: the reason that an unusual number of Canadians have turned up as major TV network anchors in the US is because of their neutral, unaccented prestige pronunciation. The networks wanted to avoid any obvious US regional accents in their national broadcasts.
I was not aware of the existence of this remarkable fluid when making my previous pronunciation decree. This decalcifying liquid should definitely be referred to as “dee-cal”, much as a delaminator is a “dee-laminator”. But “decal” in the sense of a sticker? That’s DECK-al, my friend. Learn from your betters, and all ye who wander in the darkness of illiteracy shall come into the light, and rejoice at their new-found wisdom.
ditto
But I usually call it a sticker.
No, around my region, it seems like the dominant pronunciation puts the emphasis on the second syllable, but the first syllable is still pronuounced “dee-”, not “deh-”.
Me too - a stee-kerr.
Maybe it’s cuz I made models as a kid, but to me decals are those things that you slide off with water and are often transparent in parts, while stickers you peel off and stick on without the use of water. I’m not entirely sure if that’s even the distinction, but I only use decal for the one that uses water, and sticker otherwise. I haven’t had much occasion to use the word “decal” in decades, though.
Should it rhyme with “fecal”?
There are similarities. Decals are shit that you apply to a surface. And the first syllable matches. But the second syllable of “decal” is an enunciated short “a” sound, as in “canal” (and similary accented, in the dalect that I am accustomed to), whereas the second syllable of “fecal” is never accented and typically, IME, rendered as a schwa sound, like “pull” (which you should not do with that shit).