Post 2,000 mile road trip removal of spark plugs. 1 quart of oil burned over the trip. Carbon flakes on the base of the electrodes. All 6 look the same. NGK BP5ES. What say the experts?
Critique the condition of these spark plugs please
- Thread starter Stevehose
- Start date
In no way an "expert" but colour is "in there" carbs are a nuisance to others, but so much fun to the rest of us. 1 US quart/2000miles, hmmm is this different than previously? In my experience oil consumption varies with revs, speed, not just miles travelled. Perhaps you have had more fun than you are letting on. 
Looks like a pretty good color Steve. The carbon at the base can change because of the way the plug is oriented in the head. The strap may be facing the intake or exhaust valve and because of the heat and or cooling they can look slightly different. Look at all the plugs. The plug could be a slightly hotter heat range and might be a little lighter in color but we only get a few choices. I've messed with that some but because we have the screw top plugs there are less choices.
I ordered a set of BP4ES which is hotter than the hotter BP5ES to see if it helps with the carbon. I am mostly city driving with a lot of fuel squirting into the Webers with each accel.
I’d say your mixture is good and your engine is worn. Looks like your high revs are keeping the top of the plug from fouling but no help for earth electrode. When in doubt- smell the plug....if it’s oil fouling, it will smell like engine oil.
why BP5ES .?
i use BP6REIX, OK it is itidium, but it is a 6 and not a 5, i heard that 6 was the recommended value for our coupes
BP5ES is nonresistor version of BP5RES which is a hotter plug than BP6REIX, I use because I do more city type driving which I have read can benefit from using a hotter plug to resist fouling.
The only difference I see in the platinum versus iridium is their life expectancy. I guess if you drive your coupe 100,000 miles in the next year or so then great.
With the few thousand miles we drive if that, then there is really nothing to gain except you can say your car has iridium spark plugs.
What coupe manual recommends iridium plugs.
With the few thousand miles we drive if that, then there is really nothing to gain except you can say your car has iridium spark plugs.
What coupe manual recommends iridium plugs.
Are you certain the guys at JiffyLube put the correct weight oil in at your last service?
Looks a lot like 0-30 residue in a car that should have 20-50. Happens all the time!
Hah! I definitely use 20-50, VR1 ordered by the 12 pack from Amazon. But the residue is what I question also.
I could send my leak down kit to you (and maybe your carb tool too!)
If you want to try it.
If you want to try it.
I'll change plugs and run a compression test and run it for a while and then check the plugs again, then I might hit you up. Thanks.
Steve, I have leak down test gauges too if you need to borrow them.
With the M motors this is the real test. Usually the test you don't want to do because the results are a head rebuild.
If your motor is running well and not smoking a lot then you might want to just keep driving.
With the M motors this is the real test. Usually the test you don't want to do because the results are a head rebuild.
If your motor is running well and not smoking a lot then you might want to just keep driving.
It does run well with no smoking and burns very little oil so not too concerned. Just realized I haven’t pulled those plugs in 2 years to check them since I first installed them. Appreciate the offer.
The only difference I see in the platinum versus iridium is their life expectancy. I guess if you drive your coupe 100,000 miles in the next year or so then great.
With the few thousand miles we drive if that, then there is really nothing to gain except you can say your car has iridium spark plugs.
What coupe manual recommends iridium plugs.
+ iridium plugs give better/bigger spark
Color looks good to me too Steve. As to the carbon issue, you might consider an oil analysis: https://www.blackstone-labs.com/?se...abs.net/Bstone/(S(f5yd5pjsmokn0w45xzzv5345))/
carbon fouling: https://www.ngk.com.au/technical_info/analysis/
Carbon fouling is the most common spark plug related failure, but is not a spark plug fault. Carbon deposits are conductive, and as they accumulate along the insulator nose they reduce the insulation resistance of the spark plug. As electricity always takes the path of least resistance a misfire may occur if a significant amount of carbon deposits accumulate. A spark will not form as electricity can track along the conductive carbon deposits to the metal shell (as shown in red below) rather than forming a spark across the electrode gap which has a very high resistance.
As mentioned the optimal operating temperature range for a spark plug is 450 – 870°C, 450°C is the spark plug self cleaning temperature at which point carbon deposits will burn off. However, if too cold a spark plug is used and this temperature is not achieved carbon fouling will occur. This is the most common reason for carbon fouling.
Carbon fouling is the most common spark plug related failure, but is not a spark plug fault. Carbon deposits are conductive, and as they accumulate along the insulator nose they reduce the insulation resistance of the spark plug. As electricity always takes the path of least resistance a misfire may occur if a significant amount of carbon deposits accumulate. A spark will not form as electricity can track along the conductive carbon deposits to the metal shell (as shown in red below) rather than forming a spark across the electrode gap which has a very high resistance.
As mentioned the optimal operating temperature range for a spark plug is 450 – 870°C, 450°C is the spark plug self cleaning temperature at which point carbon deposits will burn off. However, if too cold a spark plug is used and this temperature is not achieved carbon fouling will occur. This is the most common reason for carbon fouling.
I have NGK BP6ES based on recommendations I heard about over the years. I have one cylinder that gets black probably from oil; the rst are grey/brown. Couldn't get Bosch plugs to work strangely enough.
I think NGK plugs are superior to Bosch, especially the ones not made in Germany (which are getting harder to find-much easier to get NGK locally).
i agree with Steve that if you can not get original WR7DC BOSCH MADE IN GERMANY, the best alternative is BP6ES NGK