Plugs & Mileage

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Cheesehead - 06 Sep 2005 17:15 GMT

Here's the scenario
    The plugs in the E320 were Bosch Supers.
    I changed them to Bosch Platinum 4s.
    Fuel mileage dropped from 29mpg to 26mpg.

One hypotheseis is that the Platinum 4 plugs require more voltage
and so were desaturating the coil. As a consequence, not enough
spark for a good burn.
Another is that they were too efficient, prompting the computer to
input more fuel, thus increasing consumption.

(Last night I changed back to the Supers.)

What are your thoughts on this?

Collin
KC8TKA
E320/97

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Pete Stephenson - 06 Sep 2005 19:20 GMT

> What are your thoughts on this?

I'm not sure...a 3mpg drop in mileage seems to be within the margin of
error. How many miles/tanks did you go through to do the calculation?
Same driving conditions on both?

Might it be worthwhile to purchase another set of Bosch Supers and
seeing if you get the same mileage?

Or, like me, you could get a diesel and not worry about spark plugs. :)

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Pete Stephenson
HeyPete.com

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Cheesehead - 07 Sep 2005 13:16 GMT

I looked for a diesel but couldn't find one when I really needed a car.
A few weeks earlier there as a 300D/2.5 in the area, but not at the
right time.
If I could trade this car even-up for a diesel, it would be a nice
thing.
The car just needs that little bit of TLC which will take me a couple
of months
to work through. But other than that, it's certainly good to drive.

Collin
KC8TKA

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T.G. Lambach - 06 Sep 2005 23:31 GMT

29 mpg ought to be verified - seems very high.

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Cheesehead - 07 Sep 2005 12:22 GMT

Not really a high value.
That was measured for almost 2 months driving to / from work. All
highway.
Including a cross-country trip to Wisconsin -- 10 hours each way.
And my brother's 86 300E got 32 hwy regularly.
I can understand 25mpg in city/hwy mixed drivning. But straight hwy
can be 29+ with ease.

collin
kc8tka

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Wan-ning Tan - 07 Sep 2005 04:46 GMT

I am not sure about this 97 E320 engine. My 96 C280 has M104.941 which
is inline 6-cylinder, DOHC. I think M104 also has a 3.2 liter version.

My M104 has to use Bosch Super because its spark circuit design includes
the plug resistance. Platinum plug has different resistance and will
cause misfire.

> Here's the scenario
> The plugs in the E320 were Bosch Supers.
[quoted text clipped - 14 lines]
> KC8TKA
> E320/97

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