Took my 2003 Pontiac Vibe to the shop today and had the spark plugs changed. The shop used double platinum and when I noted that the manual had called for iridium, I was told that they work more or less the same. Car seems to start up and run ok but I was wondering if anyone else had any experience with this or can vouch for whether this is true?
The double platinum will probably work but aren't optimal. They're about half the cost of iridium, so sounds like the shop took advantage of you. Iridium plugs are OE and no idea what if any long term effect running the platinum would cause you. I'd swap them out with NGK Iridium as soon as possible if it was my car.
All spark plugs work the same; voltage jumps the gap causing the spark. When the voltage jumps the gap there is wear to the metal surfaces at the tip. Different metals wear at different rates. When the metal wears away the gap of the spark plug grows wider. This makes it harder for the voltage to jump the gap and puts added load on the coils. This is why spark plugs wear out and need to be changed. The difference in these spark plugs is the material that is at the tip of the spark plug hence the platinum, iridium, steel, etc. which effects how long the plugs will last before needing to be changed again.
If you have a 2003, it probably does not need expensive spark plugs that will last over 100,000 miles again. How much longer are you going to have the cars and how much money do you want put into it are some questions you have to ask yourself. The double platinum plugs will last 100,000 miles anyways so I would just leave them.
p.s. Also gtv237 is one of the people on this board who's answers are spot on and should be taken with higher regard. He is a great asset to this forum.
p.p.s. From years ago experiences with spark plugs, I would not put Champion spark plugs in anything unless it came with Champions from the factory. Any other brands are fine.
The devil is in the details.
Unless you've modified the engine the safe bet is to use Denso or NGK plugs of the same part # as original.
This is true of any of the Japanese engines.
Personal opinion: stick with OE on anything built after 1996 where you have OBD-II. I used to work as an auto technician, and found that when sticking with OE you will bet the best performance and longest service life.
I second the opinion about Champion. I will also add that I will not use Bosch in anything that does not use Bosch from the factory. I have seen misfire codes caused by Bosch plugs, specifically when people replaced a stock plug with a multiple electrode plug.
Honestly, NGK is one of the better spark plugs out there.