Did'nt know about the octane stuff, all I knew is ran like do-do on regular. But I have have run the high dollar stuff since I found out it would not run worth a flip on the regular with out these problems. How many miles can you get out of a set of plugs? The owners manual says change every 8k but when I changed them at 12k they looked like new with a nice brownish tint to them.
1st up,if your stock low comp 07 R* as you put it (" would not run worth a flip on the regular "
meaning 87-89 octane fuel then there is something wrong with it.
The low com R* is specifically designed to run on low grade 87 octane fuel and due to its low comp & combustion chamber design running high octane premium fuel actually degrades its perf while also at the same time causing excessive carbon build up in comb chambers /valves/pistons/ex system too.
Its likely a carb
fuel calibration/setup issue your experiencing needing to be better dialed in when it comes to PMS
/Needle clip setting/maybe even main
jet too along with also maybe needing the cold enricher/choke trim mod thats already been suggested too.
As for the plugs,even though your plugs were looking good with 12k miles on std type non plat plugs there was gap errosion and wear on center & grnd strap electordes which is why you need to change them.
I have run std ngk plugs to 8k miles no problem,could go with plat or iridium plugs that can go way more milse then std lugs can but 1st get running issue fixed before paying more money for those plugs.
But with that said i took those same plugs with 8k miles on them & cleaned them in a professional spark plug cleaner ,regaped,and then reistalled & ran them no problem to 15k miles & then installe NGK iridiums.
And post plug cleaning i also took the time clean all cleaning debries out of plugs post cleaning spraying carb cleaner deep into plugs then using 100psi comp air to blow it out so no issue with abrasive getting into cyls.
I have been using that prof plug cleaner for many yrs without ever having an issues as long as you always take a min to ensure you clean out all abrasive debries post plug clean/prior to re-gapping & reinstalling the plugs (use antisieze on threads) post cleaning which is very important to do.
Doing that keeps you out of trouble by keeping cleaning debires from plugs getting into cyls or plugs getting stuck in threads in the heads if not using antisieze.
,Single plat plugs are rated for 60k miles,dbl plat & iridium plugs are rated for 100k+ miles in fuel injected cars ,but in the carb'd R* with less then optimal efficiency it could be a bit less.
But even getting half that in our R* like maybe 50k miles using dbl plat or oridium plugs is a heck of a lot better then getting only 8k miles or even 15k miles with cleaning like i did of std stock type plugs.