I'm no mechanic, but I think with EFI and ECUs in charge of what goes on inside a motor, plugs of any kind will last forever (almost ever) if used for riding on the road. The shop change out my plugs at 10k just because the routine calls for it. They looked like they were just getting on a roll. Forgot to mention that these were the cheapest H-D plugs

 

Not in my experience. My EFI bike developed a miss at 6500 miles with the original HD regular plugs. I replaced with the same and got the same results.

 

Then I'd look for a problem somewhere else as plugs going bad are probably a symptom. In the past, wow it'll be 3 years next month, I've put over 10k on 3 different Harleys and haven't had a plug problem yet. Had the prepaid service plan on one of the bikes, bad idea, and they change the plugs at 10k. They look great and while I should toss them, they're in the tool chest as backups. For what, I haven't figured out yet. Now I had a 65 Chev with the 327, that was an engine that devoured plugs.

 

stick to your "over the counter" stock plugs...this nickel & dime mentality blows me away...you can buy two for the price of a Starbucks latte...youmay need a different sized spark plug socket if you decide to change..

 

I spent hours in the Dyno one afternoon testing different plugs to see which worked best and believe it or not the stock and gold plug worked best. I recommend the gold because it has a coating for longevity and to resist fouling. Plugs tried were Autolite, AC, HD Gold, Stock HD, HD Dbl Platinum, SE Perf Plug nd stock Splitfire.

Have used Nitro plugs lately and willshow 1-2 p increase in Dyno depending on combination. Essentially it is a Autolite plug that has been Cryo'ed. Remember to gap 36-38. Any more is for emmissions.

 

I don't know what the problem could have been with theregular plugs. The first set was missing at 6500 miles on the clock. The second set of them was missing at 13k miles on the clock. (BTW, this wason a stock motor.)I've ran it up to 64k miles now using platinum plugs and never had any problems.

 

COST. PROFIT FOR MOCO.

 

Well, it looks like you've found what it takes to make you motor happy. That's what counts, right? So if those plugs are working well over bowcoup miles, then they are also a bargain.
I see you have a DFO on your bike. I bought my RG just last year with 20k on it and Plat2s installed. I was cautioned not to mess with the DFO as it had been dyno tuned. Finally said to heck with that as it was doing a lot of popping on decel. Reset the Green pot from 4 to 5 to see what effect it would have. We did a 130 mile lunch ride today and my pals asked me where the POP went. Running great, but I'll miss it because it was super for setting off car alarms going through town.

 

I've only been running the DFO for the last 12k miles. I didn't need it until I swapped to Duals and then needed to enrichen the fuel circuit. My bike popped on decel with the stock headpipes and Stage I. It popped for 54k miles. It would pop so bad when rolling off the gas on the interstate that 12 inches of blue flames would come out of the right pipe.

 

just use standard HD plugs or similar, expensive plugs are, well, just expensive, and wont make any appreciable difference in the real world.