What are the best spark plugs to use? Do any give better mileage or perfomance? I ride a stock 08 ultra....

 

I can't make a recommendation, but I thought I would pass this chart along anyway.

 

Contrary to advertsing, there is no such a thing as a spark plug that can make HP or offer better fuel economy. OE plugs are designed for optimal performance. Plus using a diffrent plug may change the ion sening on the knock system. OE plugs for HD is Champion copper. I know from GM ecotecs, if you do not use Double platium plugs, it would throw a code for misfire. In HDs it would not do that. But why use something other than copper plugs? I could see uning a platinum, if it was hard to get to the plugs, but in our case it is not so. Diffrent brands are ok, but looking at diffrent brands, Champion has a longer insulater for a hotter burn, compared to others. In my EVO I had to use Champions, for other brands would fould out.

 

I use Autolite 4164's for a heck of a lot cheaper than the HD OE's, never had a problem yet.

 

Someone makes the OE plugs, anyone hazard a guess?

 

You might want to do a search and read up on the Ion Sensing System used to control detonation on the electronic bikes.
Best thing you can do is stick with the stock plugs and wires.

 

this is an argument that go on forever and nothing change like an oil thread... But I have found NGK Iridiums the best to liking .. Is what use on my Electra and Sporty both and used it on the Heritage as well with no problems whatsoever...

 

dont mess with success, harley plugs are fine, 5 bucks a piece and good for a year. waranty may be a problem if direct cause. dont use any after market plugs wires from what i have read on the forum

 

I have played with a couple different brands,but stock is best..

 

When I sold my 2000 EGS in January of this year,it had H-D platinum plugs(6r12pp) with 77,000 miles on them and they were still sparking like they were supposed to.The bike had a total of 88,600 miles on it.I did not over use the choke.On a FI bike the plugs should last a long time with many miles on them.