Here is a question that is sure to start some spirited discussion.
What effect will gapping the plugs to .39 have?
Here is the background...
I changed the plugs about 4 months ago. I used the NGK's that OhLord suggested. (By the way they work great). When I got them I was checking the gap on them and they were all .39. Well the specification is .32 so I dutifully regapped all 12 to the specification. I have noticed that my mileage seems a little low compared to others around the site (22mpg for a highway trip of 640 miles). I attributed that mostly to the fact that I had the cruise set between 75 and 83 most of the way. I have been wondering though if the bigger gap might not produce a considerably cleaner burn and thus an increase in mileage.
What are everyone's thoughts?
Drew
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"Timeo Danaos et dona ferentes" - Virgil, The Aeneid, Book 2
gap is .39-.40(1mm) where did you come up with .32?
never gap plat plugs leave them as gapped out of the box.it is a high energy ignition system and closing down the gap will stuff the spark. Also to anyone else never use the multi tip plugs.
ohlord
buy 12 more and install them
Here is a question that is sure to start some spirited discussion.
What effect will gapping the plugs to .39 have?
Here is the background...
I changed the plugs about 4 months ago. I used the NGK's that OhLord suggested. (By the way they work great). When I got them I was checking the gap on them and they were all .39. Well the specification is .32 so I dutifully regapped all 12 to the specification. I have noticed that my mileage seems a little low compared to others around the site (22mpg for a highway trip of 640 miles). I attributed that mostly to the fact that I had the cruise set between 75 and 83 most of the way. I have been wondering though if the bigger gap might not produce a considerably cleaner burn and thus an increase in mileage.
What are everyone's thoughts?
Drew
Over the decades, many enthusiasts have tried larger gaps. Some with more success than others. MSD has a website with some good info to glean from. There are some posters there who have shared their experiences with larger gaps. NGK is also another website for info. Ditto Bosch, Denso, and etc.
Some ignition systems are not compatible with larger gaps. Even though other ignition systems will work with larger gaps, it isn't always better since after a short while, the performance gain will be lost.
I believe the ignition system equipped in your 1998 E320 uses high tension leads. I would suspect the resistance would range in the hundreds to thousands of ohms. Usually for ignition systems that use high tension leads, bigger gaps can be used.
For coil-per-plug ignition systems (no high tension leads), the recommended gaps are usually smaller. ie. 0.032" for a 97 E420.
Incidentally, NGK recommends 0.039" gap for your vehicle. You can go to their website and verify it for yourself.
You can re-gap your spark plugs with no lost in performance or life.
Usually the benefits that accompany a stronger ignition system performance is better throttle response, better small throttle opening acceleration, and better fuel economy.
Are you using the NGK G-Power series spark plugs (fine platinum center electrode, single-sided)? Also, if you don't mind, can you post a photograph of the tip end of one of your plugs, should you decide to take them out?
Well I thought it was odd that NGK would come for my car at .039. I am just wondering why the manual says that. Maybe my vehicle is an early production run and MB changed the gap part way through. All-Data says .039 as well. Well it looks like I will be changing them out! Could be the problem with lower mileage.
suggested. (By the way they work great). When I got them I was checking the gap on them and they were all .39. Well the specification is .32 so I dutifully regapped all 12 to the specification. I have noticed that my mileage seems a little low compared to others around the site (22mpg for a highway trip of 640 miles). I attributed that mostly to the fact that I had the cruise set between 75 and 83 most of the way. I have been wondering though if the bigger gap might not produce a considerably cleaner burn and thus an increase in mileage.
Linear Mode
