Spark plug choices?!

Most plug gaps are pretty much spot on these days, the vehicle manufacturer pretty much goes with the plug manufacturer's standard gap.

Just as well as on my other car the plugs have 3 cathodes arranged around the central anode, I wouldn't want to start trying to gap those, I don't think you would ever get them all the same.

I have read that NGK has an upgraded spark plug from the Premium RX to the Ruthenium HX.  I can not find a cross-reference between the two.  The specs for the Premium RX (DCPR6ERX-11P / 90558) are: Thread diameter: 12mm Thread reach: 19mm Seat type: flat Hex size: 16mm
Is there a Ruthenium HX model that matches this spec?
Or, am I way off with my understanding about these?

I fitted the Denso iridium ones.  A bit cheaper than NGK and I found a marginal improvement in mpg with them in other cars.

I don't know if Denso supply Suzuki but they supply a lot of OEM parts on Mazdas etc.

In 2021 I bought a set of NGK Iridium IFR6J11, 4 for £52 for my 2011 Gen3. I fully expect them to last the life of the car, but if they do need replacing it won't be the tip that has worn out, it will probably be oil fouling or some other type of damage.

Iridium are meant to be good for up to 100k miles.

Ruthenium tip are meant to last longer and give slightly higher performance, whilst this might be true of a modern car engine where fuel efficiency and performance is much higher I doubt it will make any difference at all to a Jimny.

The longer electrode life will be of limited benefit as something else will wreck the plugs, like oil fouling, over-heating or muck and dust on the outside so I doubt you will see any benefit.

However, see how much they are and if they are about the same price as Iridium (or cheaper) then go for it, just don't expect to notice any difference over a decent set of ordinary or Iridium plugs.

By the way I couldn't find any for sale in the UK to fit a Jimny, there seemed to be some in Japan though.

Robin

Don't overthink spark plugs. All Jimnys have very basic, low performance engines. The only benefit of more expensive plugs is lifespan, but that is reflected directly in the cost. And if you don't change your plugs for a decade, you may find them reluctant to come out which can lead to much bigger issues. I use standard copper plugs in my Jimnys. They are £20 a set and look good as new after 2 years/20,000 miles.