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I just flipped 100k on my E55 and as I understand it, that means it's spark plug time. It runs fine, smooth, get 21.5 MPG hwy. I've only had it for about 5,000 miles and I don't know when/if plugs were changed.
I went through threads as much as 10 years old and the "recommended" spark plug has changed, a lot. 5-6 years ago people said Iridium was a waste of money with no benefit, now I'm seeing NGK LFR7AIX # 2309 has been popular in the last 2-3 years. So, is the NGK still the plug of choice or is it something different?
Right now the motor is stock short of a belt wrap kit, but I'm considering a tune and maybe headers down the line.
NGK LFR6AIX or 7, depending on mods. Personally I run 6's and never see over 1100F EGT.
I would have to look again but I think there was a big price difference in 6's and 7's and I don't have mods and the mods I'd do are minor. 6's were higher I think, is there any disadvantage to running 7's on a stock motor?
I'd like to buy local so I can swap them by Thursday night for a Friday trip but finding them local has been tricky.
EDIT: After looking, the 6's vary in price a good bit between local and ordering. To verify, these are the ones, right? https://www.ngk.com/product.aspx?zpid=9871 Everything says those don't fit the car, though I realize if people use them, they fit.
EDIT 2: Said in stock till I put qty 16, they have 2. So apparently spark plugs local for this car are impossible.
The reason for colder plugs is to transfer heat to the cylinder heads so the coolant system can carry the heat away, however if the plug is too cold then it won't burn off deposits.
Stock to nearly stock the 7's should be just fine as that is what is OEM.
The reason for colder plugs is to transfer heat to the cylinder heads so the coolant system can carry the heat away, however if the plug is too cold then it won't burn off deposits.
Stock to nearly stock the 7's should be just fine as that is what is OEM.
6's are OEM, but the side effect of being too cold isn't worth the risk. You don't need to go colder till 75-100 HP gains and the 2 most likely things I'll do would yield around 80 HP combined so 6's seem like the way to go. I did manage to round up 16 LFR6AIX-11 locally after they brought them in from 3 other stores (4 stores total) today. So, if I can get inspired and when my motor cools off I'm going to swap them and see what I gain from it.
After looking around I found that there the main difference between the ILFR6A and the LFR6AIX is that the ILFR6A (OEM) ground electric core is copper and the ILFR6AIX uses nickel.
It may not make much of a difference, but there are differences between the two parts.
I would love to hear from someone with more experience concerning the practical differences between the two parts.
You missed a few other main differences, like electrode size, gap size, and resistance.
My assumption is the the resistance is directly attributed to the change in ground material, as copper has much lower resistance than nickel.
I included the summaries together so that it was easy to see the differences. There is no side by side comparison on the NGK website, so I thought this was a good A/B comparison.
As far as the gap, I don't consider that a significant difference, as I would never install plugs without verifying gap, and adjustments are not uncommon. I would even suggest that we could have a considerable discussion as to the optimal gap.
I'm half way through swapping plugs (had to come back inside and do some work for a bit) and I've made some observations that may or may not effect my results of the swap. I'm finding some plugs that have wet oil on them, not on the electrode but at the gasket. Some on the gasket, some just above the gasket. Not all of them are requiring the same force to come loose. The ones being taken out are genuine MB plugs, so they might actually be 100,000 miles on them. I'm putting the new ones in consistently with 15 ft lbs. It's possible I may have been losing some compression from improperly torqued plugs.
Some driving on the LFR6AIX-11's I put in and it looks like I may have gained some city mileage, however, I might have lost some highway mileage. I will have more highway data this weekend for comparison. The driving I did Saturday I only got 20.4 MPG when that same drive I normally get 21.5 MPG.
You might want to reset you computer if you haven't already done it. It's quick and easy (and free!), I assume that new plugs would respond better to the factory settings over it's learned settings.
You might want to reset you computer if you haven't already done it. It's quick and easy (and free!), I assume that new plugs would respond better to the factory settings over it's learned settings.
I did that too a day or two later, well, the "hidden" method, not a battery disconnect. I just got a phone call for work that means I get to drive 200 miles right now so I will test the same route of highway and see what I get this time. The place I filled up before gets surplus fuel so who knows what I pumped other than 93 octane, it might change with different fuel.
Today's 200 mile drive, I did manage to get to 21.0 briefly, higher than before but not the 21.8 I did once or the 21.5 normal. I'll have another 400 miles this weekend so I will monitor it again with different fuel. I'm starting to think I may have simply gained about 1 MPG city and lost about 0.5-0.8 highway.
After a few highway trips and some more city driving, I have concluded compared to the OEM spark plugs, the NGK LFR6AIX-11 gives me ~1 MPG city gain, but ~1 MPG hwy loss. Driving experience doesn't seem any different. Not a waste of money but my dreams of seeing 22 MPG have been shattered, I was so close!
08-30-2016, 01:36 AM
