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Discussion Starter #1
Dropped in a new set of Laser Platinum plugs in my 98 SLK230...
I love the quicker response now with these compared to the Bosch F7KTCR ones I pulled out... only 28k on the car, but I wanted to try this.
Must say it is feeling a lot quicker off the line than it was before!

I'll be running through a tank of gas or two this weekend to see if the gas mileage improves and if the pep is still there :)

NGK PFR5A-11 (Laser platinum) - 4588
Cost - $12.50 each or $56 CDN taxes in for all four...from an auto store in town.

I thought I had a problem with my plugs anyway as the insulator shell was turning yellow at the base of all the plugs, but turns out is normal for these engines...it's called corono stain
Strange as my C230 had only two plugs like that and not all four...
PLUG STUDIO / NGK
Corona stain | NGK Spark Plugs UK
 

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Registered 1999 SLK230
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75 Posts
wow, that's awesome... I've never noticed a performance improvement on a plug change (talking other vehicles though, not an SLK)... thanks for the tip!
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Registered 1999 SLK230
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that's interesting too... although I'm pretty puzzled about the gas requirement in the first place... I think I read somewhere compression is 8:1? which certainly doesn't warrant 91 octane in a normal engine build...
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Whatever the owner's manual says for recommended octane is what should be used.
did u get a 1998 owner's manual with your car? manuals older than (earlier) 2000 are hard to find
 

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Registered 1999 SLK230
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Ironically I have two manuals (but only one key ;) )! Manual says use 91 octane.
I also have an inquiring mind...
Seems the compression is 8.8:1
here's a typical compression/octane chart so you can see why I'm curious of we're using 91at 8.8:1


I'd love it if someone chimed in and said 'use 91 even though you have 8.8:1 compression because (insert technical reason here)'
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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You should use 91 if the manual says so. I have to use 93, I have a V8
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Discussion Starter #11
Quick trip mileage results

When I changed the plugs I also decided to drop in a new set of wires and a new set of coil packs... (when I changed the plugs one of the coil boots would not pull up and I ended up tearing the boot so decided to just put a new set of wires and new coil packs in). They supplied me a set of NGK 54001 wires, but the wires weren't long enough if I used the plastic loom so I just ran the wires right beside the coil pack to the ignition coils. Thicker silicon casing wires so hopefully no problems with running the wires over the coil packs.

Results:

First fill up
375kms
7.985 L/100km
29.46 MPG (US)
35.29 MPG (CDN)

2nd fill up
521kms
7.813 L / 100km
30.10 MPG (US)
36.01 MPG (CDN)

Country driving on windy, twisty and hilly roads... speed limit was 80km/h (50 mph) which means 100 km/h (60 mph) for 75% of the trip until the last stretch of the trip and then 100km/h limit which means 120 km/h (75 mph) :)

City driving - will report back, but guessing with my heavy foot in town there won't be much of a change.
 

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Discussion Starter #12
91 and 93 octane

I normally use 91, but dropped in a full tank of 93 tonight after my long distance runs. No reason to do so, but thought to give it a try...
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Use that techron and be surprised.
 
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