spark plug change interval for expensive plugs

Have a '91 Honda Accord. The last set of spark plugs I installed were http://www.boschautoparts.com/Products/SparkPlugs/Platinum2.htm. They currently sell for $5 ea. at the local Advance Auto Parts store (http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Spark-Plug-Bosch_11430014-P_960_R|GRPTUNEAMS_823625473___). These plugs have been in the engine for about 40K miles now.

I'm wondering whether these plugs can be expected to last a lot longer than less expensive plugs or whether they should be changed around the interval recommended in the user's manual.

I've noticed a slight roughness in the engine upon start up from a dead stop and when initially starting to accelerate from a gentle cruising. I imagine this could be attributable to various causes.

I recently changed the distributor rotor and the fuel filter. The car has 271K miles on it.

Just my .02 cents, but in my experience, Bosch plats suck nard.

Every engine I ever put them in exhibited jittery idle and cold start difficulty.

I had people pay me to pull them out and replace with OEM in the shop.

I'd suggest ND or NGK plugs, and don't use plats if not called for originally. They never seem to improve anything, and sometimes cause minor performance issues.

Correct OEM-type replacement for yours is non-plat NGK V-power ZFR5F-11

I assumed an LX Accord.

Every engine I ever put them in exhibited jittery idle and cold start difficulty.
Oh really! I'm surprised to hear that. As I said, I've had them in a good while and, except for the recent abnormality (which I can't say for sure yet is due to aging plugs), I did not have jittery idle and cold start difficulty.

Correct OEM-type replacement for yours is non-plat NGK V-power ZFR5F-11OK, thanks for that info. I may visit the local Advance Auto tomorrow and get 4 NGK V-power ZFR5F-11 (http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Spark-Plug-NGK_5390273-P_960_R|GRPTUNEAMS_542699353___) plugs.

Yeah they work well in newer engines designed to use them, with high degrees of oil control and fuel trim...

But in older and high mile engines and especially carburetor equipped motors they don't seem to tolerate residue fouling as well as conventional plugs.

All the Bosch plats I've seen have a very thin firing tip wire that is recessed. I suspect that's somehow responsible...

http://www.boschautoparts.com/NR/rdonlyres/62145AEA-97AC-483E-88DE-98697185BF3E/0/platplus153.jpg

Bosch plat tip

http://www.ngksparkplugs.com/images/tip/ngk55A.jpg

NGK Plat tip



I've put a lot of plugs in a lot of motors...overall going with the OEM type plug gives the best results. I always put NGK/ND in Asian cars, AC/Delco in GM, Motorcraft/Autolite in Ford, Champion in Chrysler, etc...

If you really wanna run plats, I'd suggest going with the NGK version for your application...

Correct OEM-type replacement for yours is non-plat NGK V-power ZFR5F-11

I assumed an LX Accord.I did get this plug. Now that I've installed the new plugs, replaced the fuel filter and the distributor rotor, the car is running better. I've also noticed an improvement in fuel economy; it's back to what it used to be and what it should be.