Do those iridium/platinum/quad fire spark plugs REALLY give you better mileage and power?

they may or may not

The platinum/iridium plugs are designed to slow down electrode erosion. The thinner elecrodes give you a smaller flame kernal, though, that is subject to being “blown out” in a turbulent combustion chamber i.e. high-swirl design, supercharged, or nitrous injected. The multi electrode plugs …….if they foul, they’ll stay fouled….electricity takes the path of least resistance. All that being said, the E3 plug looks to be a bit more promising with it’s larger flame kernel.
Remember how the “Split fire” plugs would supposedly give you 5% better fuel economy? Well, you’d need to be gettting 20 MPG to see a full 1 MPG if you do the math……The E3 is just kind of an evolution of the SplitFire tecnology as it relates to the size of the flame kernel.

your better off to stick with what it calls for. those kind are a waste of money.

Internal combustion consist of air/fuel & spark. In theory a cleaner or more efficient spark will burn fuel at a better rate thus saving fuel. Either way majority of today car come with platinum tip spark plugs that why some manufacture has a 100,000 miles interval until a full tune up is required. We all know certain materials has better conductivity like gold or platinum etc.

Not enough that a normal person is going to notice any real fuel savings in the real world.

If you are in a test lab then maybe you could measure some improvement under some conditions.

no,they last longer.but if the plugs you have are worn out you might notice a difference

I have found that LPG is very sensitive with spark plugs to get good starting and long term smooth running. So after a lot of experimentation with different types (splitfire, bosch four electrode, NGK, NGK iridium etc) I have found Champion copper core to be the best by far and they’re cheap as chips! (I’ve also seen dyno tests showing a small, 2 bhp on 115 Bhp engine, increase with the champion copper core against splitfire and all others) One improvement I have found is to file the side electrode down, to half cover the centre electrode so the spark jumps from the newly created sharp edge and onto the middle of the centre electrode. This gave a good starting and light load misfire improvement on LPG probably due to improving the access of the fuel to the spark, for no real cost except the plugs may wear out quicker but as they’re cheap enough it’s no problem.
With an eye on the pennies I just file them to sharpen them up, re gap and continue on.
On petrol I just leave them standard but always use the Champion copper cored.

With all that said, I have to report that fitting an NGK iridium VR plug to my 250cc two stroke off road bike made a huge difference to the crispness of the throttle response, didn’t work for the car though. Go figure!