Bosch Platinum Spark Plugs

Post by **Ozark Lee** » 08 Nov 2006, 17:41

For my US domestic cars the Bosch platinum plugs have been a gold standard. On day two after buying the 850 I installed new plugs and went with Bosch Platinum 2's. Over the last several weeks I have watched my gas mileage decline from, give or take, 30 MPG to closer to 20 MPG and I had picked up a noticeable rough idle. Overall acceleration and top end when passing seemed like it was gone as well.

Due to the knowledge of this group I found that Bosch platinum plugs are a real bad idea and I purchased a set of FR7DC plugs. Around here they were only available at NAPA without a special order.

This is what a Bosch Platinum looks like with roughly 1000 miles on it in a Volvo 850.

Next step was to buy a couple of cans of Seafoam which had a rather dramatic impact in the first 20 miles just adding it to the tank. I bought a can to run directly through the intake but I think I'll save that for the next trip to the cabin. My suburban city neighbors, more or less, turn a blind eye to my driveway auto repairs but I think they will get all bent out of shape if the smoke from intake injection is as bad has been described. At the lake folks are way more laid back.

When Bosch Platinum Plugs are discouraged, believe it.

...Lee

Post by **luketrash** » 08 Nov 2006, 18:03

I ran half a can of seafoam through my '54 Ford sedan last year (223ci inline 6 engine) and the smoke wasn't THAT bad. Nothing like you hear stories about online. I was just drizzling it down into the carb as the car ran and operating the throttle by hand.

Post by **MadeInJapan** » 08 Nov 2006, 18:13

With our cars, it is recommended that half a can be sucked in through a vacuum hose and then cut the engine off and let it sit for 10~15 minutes, then crank her back up. I think it's the sitting that causes so much smoke.

dasapir · Post by **dasapir** » 08 Nov 2006, 18:56

As long as we are on spark plugs, I have a question. A short while ago, prior to my car overhaul, I purchased NGK iridium spark plugs for my s70 turbo from advanced auto parts. A couple of weeks later I noticed that FCP Groton does not recommend irridium plugs for turbo volvos. I called them and asked them why not and their answer was that they "run too hot for a turbo." So I called NGK technical support and spoke with them and they looked through their data and could find nothing to support that. From my understanding of the way a plug works and the simple physics I cannot understand FCP Grotons reasoning. Therefore, I still have the plugs in the car.

I know MIJ continues to recommend OEM, However, does anyone have any further knowledge or personal experience the NGK iridium? Denso makes one specifically for the volvo which I cannot believe would be vastly different than the ones from NGK (though again there are those who suggest asian for asian cars, american for US cars etc..).

By the way, for whatever it is worth, prior to the NGK I had Bosch platinum in the volvo with a noticable change fro the original OEM. The car seems to drive better with the iridium . Have not checked milage though.

petershen1984 · Post by **petershen1984** » 08 Nov 2006, 22:00

A note on Spark plugs - just because the manufacturer Bosch says this plug will fit [insert list of cars/engines here], doesn't mean they are properly gapped for a specific vehicle. Volvo OEM plugs -- may still be produced by a third party, but when third party plugs bear the Volvo name, they will be properly gapped and have the correct heat range for the engines listed.

Post by **luketrash** » 11 Nov 2006, 09:39

A little late here, but yesterday I put in new bosch OEM plugs (old fashioned kind with only one contact.) I was surprised to find Volvo brand plugs in the car that had 4 conductors (look like Bosch Platinum +4)...

So at least I feel a little bit better knowing SOMEONE that owned the car before me had it serviced or worked on at a dealership.

Anyway, the 4 tips were burned away a bit on most of the plugs.. None were missing (good!)

The car runs a bit better with the regular old Bosch ones I put in, but it could just be because they are new. No idea on the miles on the old ones.

My car ran about the same with either though..

No idea about gas mileage without a fully functional odometer, and this airbox thermostat issue where I'm sucking in hot air off of the exhaust 100% of the time..

Tsquared · Post by **Tsquared** » 11 Nov 2006, 13:25

I like aftermarkert parts for my brakes, filters, and fluids. For the plugs I stick with the OEM. They are not that expensive and they work.

ckrussell · Post by **ckrussell** » 05 Jan 2012, 18:54

@ Ozark Lee -- I know this is an old post but I'm glad I found it as I just purchased a set Bosch Platinum 2's. I think I will return them for something different. Doesn't sound like you had too much luck with them

FASTR1 · Post by **FASTR1** » 05 Jan 2012, 20:45

I wouldn't use Botch platinums for paperweights! THEY SUCK all of them and every version! Their copper plugs are ok but that platinum stuff is hype and BS. USE OEM.

Anyone that has messed with MSD ignitions know how powerful they are and those lousy ass plugs left me stranded at work one night after being in the motor for less than a month firing them with a MSD 6A. Luckily I had some delco takeouts in the top of my tool box and threw them in and drove my car right to K-mart and told the manager I either get a refund or he'll find them in on the floor through the plate glass window tomorrow morning. Happily we came to a resolution before things got nasty.