oldNslow wrote on 03/18/13 at 08:57:30:Suzuki says change it every 7500 miles. Maybe they know something.
Lots of cars nowdays have plug replacement intervals of 30, 60 and 100 thousand miles. And I think that's mostly so the doggone things will actually unscrew after being in for so long, not 'cause the plugs quit firing.
Several things have changed in modern cars that allow spark plugs to last a long time....some of them don't apply to the Savage.
1) Computer/Oxygen Sensor operated fuel systems precisely control fuel mixture.
2). No lead in fuel.
3) Spark plug tips are now made form exotic metals that are very durable and resist the rounding off that old conventional plugs did. Round electrodes make poor spark.
Our Savage has a choke/throttle enrichment lever, a primitive carb, and a conventional spark plug......we don't get the high mileage out of our plugs.
Several times I have suggested that there was no need to buy an exotic spark plug for our engine - it was not going to make any more HP than a stock plug. When I found out that the exotic plugs are only a couple of bucks more than a stock plug.......I changed my mind and I installed an NGK Iridium.....it won't hurt anything....but I am not sure if it will help anything either. I would not think there is any reason to buy a $ 15.00 double or quadruple electrode plug!