Should I replace spark plugs? Mazda genuine or NGK/Denso?

Hi All,

First post on here having just picked up my 2010 Mk 3.5 Sport Tech. Really enjoying the experience. I hope this isn’t too much of a newbie question!

One thing I wanted to do having bought it privately was to get a service done on it imminently. Other than the standard service parts I was considering getting new spark plugs. It’s got 55k on the clock and I see the recommended mileage for changing the plugs is 62.5k. However being a 10 year old car, that isn’t far off the mileage mark I think it would benefit from a fresh set of plugs. I just wanted to know if this is recommended, and if so which plugs people recommend.

I see there is 3 main manufacturers: Mazda, NGK and Denso. Is there a reason I should pick a particular one of these and how can I tell the if NGK/Denso parts will fit my car. Also a recommendation of where best to purchase these would be really appreciated also.

I went the Denso route, much cheaper than NGK. Had they been the same cost I would have bought NGK because of past good experience with their products. But at half the price thought Denso were worth a try as they are a hugely respected brand.

And yes, definitely worth changing. An easier decision at £25 for Denso than £50 for NGK mind.

Yes, agreed, worth doing at that mileage. Mazda are not a plug manufacturer, of course. They buy in from the dedicated suppliers (probably NGK/Denso/Bosch etc). I don’t know if Mazda ‘brand’ the factory sparkplugs, in the same way as Ford. I suspect not as my car had NGK plugs and no record of a change. NGK are well respected brand, so I replaced them with a set of NGKs. 10 years old and well below the 60k, but it seemed like a good idea to change them. Check the NGK website for the correct plugs. As your car has taper seat plugs, check too the recommended tightening torque. For taper seat plugs it is surprisingly low. IIRC about 15Nm. Although they are supposed to be pre-gapped, it’s worth checking before you fit them. Two of the set I bought were a little on the large side.

On the mark 3 the plugs were indeed branded often with the Fomoco label indicating their origins in the Ford parts bin.

I can also recommend NGK plugs. There are different types for the 1.8 and 2.0 litre engine so make sure the supplier gives you the correct ones, mine didn’t and I had to go back and get them changed. NGK actually recommend hand tightening the plugs to seat the washer and then about 1/16 of a turn to tighten, if you don’t have a torque wrench.

Thanks for all the advice, will go ahead and get them changed.