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I am looking for some guidance on spark plug replacement for my 2014 E350 with the flex fuel option, although I have never used E85 in this car. I bought the Bosch plugs from FCP euro for the models with Flex fuel. I starting tearing into the project but I stopped when I looked at the first coil pack it was solid black plastic. My understanding is that the flex fuel cars also use a different coil pack which is black on top and white or gray on the bottom (at least on FCP's website). I put everything back together and wanted to get some more info. This is my son's car so I didn't want to start a project I couldn't finish right away. I bought the car used so I don't know if the plugs or coil packs were ever changed before. The car has about 62,000 miles on it. Any help would be greatly appreciated. Thanks in advance.
you definitely want to use parts for a flex-fuel car regardless of not using E-85, the CPU is programmed differently to run with the flex-fuel parts. I believe the actual combustion sequence is similar to the Euro version, I will check my Flex-fuel car for color specific variation in the coil packs Against my non-flex fuel car tomorrow morning and report back. they are definitely different part numbers. My daughter has it until luchtime tomorrow as her car is at the dealer
Last edited by pierrejoliat; Mar 8, 2026 at 09:32 PM.
I am looking for some guidance on spark plug replacement for my 2014 E350 with the flex fuel option, although I have never used E85 in this car. I bought the Bosch plugs from FCP euro for the models with Flex fuel. I starting tearing into the project but I stopped when I looked at the first coil pack it was solid black plastic. My understanding is that the flex fuel cars also use a different coil pack which is black on top and white or gray on the bottom (at least on FCP's website). I put everything back together and wanted to get some more info. This is my son's car so I didn't want to start a project I couldn't finish right away. I bought the car used so I don't know if the plugs or coil packs were ever changed before. The car has about 62,000 miles on it. Any help would be greatly appreciated. Thanks in advance.
Why change plugs or coil packs with that low mileage?
you definitely want to use parts for a flex-fuel car regardless of not using E-85, the CPU is programmed differently to run with the flex-fuel parts. I believe the actual combustion sequence is similar to the Euro version, I will check my Flex-fuel car for color specific variation in the coil packs Against my non-flex fuel car tomorrow morning and report back. they are definitely different part numbers. My daughter has it until luchtime tomorrow as her car is at the dealer
Mine are all black just like the non-flex fuel ones, but they are original parts at 108k miles, I did change the plugs at 60k, as Cali says they are not Bosch, they are NGK's I bought at Mercedes to insure correct positioning. Maybe the OEM manufacturer just changed the color to differentiate them from OE, or its a revised part.
Last edited by pierrejoliat; Mar 9, 2026 at 12:45 PM.
Mine are all black just like the non-flex fuel ones, but they are original parts at 108k miles, I did change the plugs at 60k, as Cali says they are not Bosch, they are NGK's I bought at Mercedes to insure correct positioning. Maybe the OEM manufacturer just changed the color to differentiate them from OE, or its a revised part.
thanks for checking that for me. Greatly appreciated
thanks for checking that for me. Greatly appreciated
@edes300 can you post close-up pictures of all 6 plugs electrodes: Ground + Tip ?
> LET'S LOOK AT :
The ground strap for un-wantedburrs
The ground strap sharp/round edges
The electrode gap exact measurement
The indexing from the thread to strap
The plugs are the most essential components for basic performance from excellent combustion.
Lean mixtures sparks are extremely difficult to produce.
> WORSENING MISFIRES:
We are facing a vicious cycle we best must stay ahead of.
Weak sparks cause misfires that in response call for lean mixtures that cause worsening misfires that earn less fuel....
That means failed ignition misfires are a very slippery slop !!
> AVOIDING MISFIRES:
The bleeding edge of igniting lean E85 mixtures is both an art & a science, it's extreme.
Misfires are easily caused by more than poor sparks alone.
Each cause has its own fix.
Let's focus on the sparkplugs while we have them in hand.
-- In the ball park of sparkplugs I under gap my electrodes at 0.7mm (+/- 0.05mm... 0.65 to 0.75)
-- Wider gaps do not produce longer sparks... quite the opposite regardless of high voltage!!
-- The spark exact timing benefit being precise. Mixture ignition must be always predictable with minimum randomness.
-- Aging hot plugs gap tend to widen with bent steel memory effect plus precious metal wear.
-- The shape of the tiny needle tip vs. more stubby platinums is used to strike across a single identical path.
Meaning that path better be guaranteed to fire up.
Take the time to assess your electrodes to perform best despite hellicious conditions.
### work over a table to prevent cracking your ceramic sparkplugs from a drop on the floor.
Don't trust dropped plugs reliability - Replace or install as No1.
Last edited by CaliBenzDriver; Mar 11, 2026 at 02:53 PM.
Why change plugs or coil packs with that low mileage?
On every MB with the M276 engine I have ever had I changed the plugs and coil packs out at or a little over 50k miles FCP sells an ignition kit by BOSCH for like $400. Well worth it.
Last edited by C280 Sport; Mar 12, 2026 at 07:58 PM.
On every MB with the M276 engine I have ever had I changed the plugs and coil packs out at or a little over 50k miles FCP sells an ignition kit by BOSCH for like $400. Well worth it.
I often wonder what people do with their cars. I have a 2010 E550 with almost 190000 miles on it. I have changed oil every 5000 miles and it runs like new.
I have changed the spark plugs only once at 100000 miles. The coil packs are still the originals and I’m not planning to change them before the first one goes out.
I often wonder what people do with their cars. I have a 2010 E550 with almost 190000 miles on it. I have changed oil every 5000 miles and it runs like new.
I have changed the spark plugs only once at 100000 miles. The coil packs are still the originals and I’m not planning to change them before the first one goes out.
You're running a M273 V8 Non-turbo multi port. It's a gentle giant with both power and torque.
Your engine type does not buildup super-heat like later GDI Twin turbo V8 setup with limited oil pressure or "hot-V8" with exhaust turbines nested in the center of the V.
Less accumulated heat helps cooling parts and seals last long. Injectors and Coils do not burn up to see a normal lifespan.
GDI engines inject gasoline during compression strokes and fire multiple sparks in piston top cavity. These gas engines can sound very much like diesel wip.
> Mixed Pros & Cons :
One of the M273 draw back is the single long timing chain with its hard-spring tensioner.
M278 has four chains with low stress hydraulic tensioners that rattle when conditions are present.
The result is a lot of good mixed with little bit of bad.
Last edited by CaliBenzDriver; Mar 12, 2026 at 11:52 PM.
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