Spark plug replacement not working out...

[zhandax]

I changed the NGK plugs that came in the car with some Bosch BKR7E last year, and I seem to be down a mile or two a gallon. Do I put new NGKs back in or go for something like the Denso? I remember reading about better mileage and all a year ago, but cannot find the posts now. Are the Denso's really better? If so, I can get the K20TXR ND for about $3 a plug. The IK20s are about $10. From what I read, the only difference is the IK20 is one level cooler a plug. Just speaking of the Denso's is this worth it and why?

[Jehu]

honestly when I put the DEnso iridiums in I didn't notice any increase in MPG. As far as I'm concerned the only thing they save you is from changing them more frequently which may be worthwhile if you consider the potential for damaging the threads but I couldn't attribute a gain in anything like MPG or HP though both were claimed... Though I suppose there could have been some very small improvements beyond my noticing I'm going to use the cheapest Bosch Coppers for the next change.

I recent;y tried a can of Sea Foam in the gas tank and noticed about a three MPG increase ... must have had gunky injectors but over several days and another can os Sea Foam that gain appears to be vanishing and i'm back pretty much to where i was... Can you use Too Much Sea Foam?

[Rus]

It would be helpful if you fill out your car information in the user profile, zhandax. 5 series cars came with many different engines over the years, each with unique spark plug requirements. Its hard to recommend anything when you can have anything from a 2.5 to a 4.0 liter engine. Personally, I use Bosch plugs model W8LCR. Fuel economy ranges between 18 and 24 mpg for city and highway use respectively. Something to consider about spark plugs is their heat range. Compare the specs for the BKR7E and the NGKs you took out. Chances are, they are different and it can have an impact on how the engine runs.

[ryan roopnarine]

seafoam has constituents in it that will increase your gas mileage in that tank. the test will be to see if the increase remains after two or three runs to empty.

honestly when I put the DEnso iridiums in I didn't notice any increase in MPG. As far as I'm concerned the only thing they save you is from changing them more frequently which may be worthwhile if you consider the potential for damaging the threads but I couldn't attribute a gain in anything like MPG or HP though both were claimed... Though I suppose there could have been some very small improvements beyond my noticing I'm going to use the cheapest Bosch Coppers for the next change.

I recent;y tried a can of Sea Foam in the gas tank and noticed about a three MPG increase ... must have had gunky injectors but over several days and another can os Sea Foam that gain appears to be vanishing and i'm back pretty much to where i was... Can you use Too Much Sea Foam?

[zhandax]

Sorry, I had it in my sig until I changed it. 1994 540i build date 03/93.

[bubba966]

Put the right Bosch's back in and it'll probably run better. Should have the FR-7-LDC Bosch in it, or the FGR-7-DQP high power Bosch plug. Not sure what differs between the high power plug and the regular one. Pelican has the regular plug at $4, and the high power plug at $5.75.

They have the NGK plug as well. And while those are also good, they're $8 a pop so they're a bit spendier than either of the Bosch plugs.

http://www.pelicanparts.com/bmw/cata...BAStun_pg1.htm

[zhandax]

That is why I didn't put the Densos in when I resealed the intake; $80 for the plugs. Do these cars need a bit cooler plug? I will not have time to do any plug research until July 4th weekend at earliest.