Spark Plug Fouling-Orange Color

[Tom]

I was corresponding with another owner who shared that when replacing his spark plugs, he noted that they had an orange color to the normal fouling process.  I noted the same thing last week when changing my plugs.

Anyone know what could cause this?  Is it a seasonal gas additive?

Thanks in advance,

Tom

[Benz Dr.]

Almost sure this is an additive.

 Possibly MMT which will make the plugs a rusty colour. Some places have banned the use of this additive but I know it's still being used here in Canada. Probably the States as well.

 Dan c

Daniel G Caron

[hands_aus]

And Oz

Bob (Brisbane,Australia)
early 250 SL, RHD

[rwmastel]

What is a "seasonal gas additive", and why would anyone use it?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[isofast]

Rusty fuel tank or fuel line or both is my guess. I had the same deal once.

First Place AACA Show Winner 350SL August 2003
I love low mile car's.
1969 280 4spd

[George Davis]

Rodd,

seasonal gas additives are required by federal or state laws in some places, mainly to help reduce carbon monoxide emissions from older cars during the winter months.  In Oregon, ethanol is the additive of choice; some places use MTBE ('though it's losing favor because of health concerns).

MMT seems to be an octane booster, so it might be used year-round (?) in those places that use it.

George Davis
'69 280 SL Euro manual

[Tom]

Dan, George, Rodd and others:

It must be the additive.  Not rust, as my system is new.

Best,

Tom

[Richard Madison]

Tom:
The link below shows fouled Bosch plugs, Number 5 has a yellow mess on the tip...

http://www.boschusa.com/images/SparkPlugFaces.pdf
Richard M

[hands_aus]

My plugs run with what looks like a sulphur coating on them all year round.

I use lead replacement fuel.

Bob (Brisbane,Australia)
early 250 SL, RHD

[rwmastel]

Bob,
Hi.  Why do you use lead replacement fuel?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[hands_aus]

Hey Rodd,

Premium Unleaded is one cent a litre dearer than lead replacement fuel and it is readily available at this stage.

Petrol prices vary depending on the day of the week. Fill it Monday to Thursday 1 litre lead replacement costs about AUD $0.82 Fill it Friday to Sunday and it costs about $0.92 or the equivalent of USD $3.10 - $3.48

At the rate my car guzzles its way through a tank of fuel any money saved is money I can spend driving it another day.

Bob (Brisbane,Australia)
early 250 SL, RHD

[LFrank]

RM - thanks for finding that fascinating ADOBE document from Bosch.

Of course, that leads to my (stupid?) question: will all six plugs be equally affected? If I pull just one and see norman gray ash (proper combustion) I don't need to look further?

LFrank
Washington DC
65 230 sl - auto
DB334/Hellblau

[n/a]

LFrank, I know you asked RM, but...

If I had reason or just curiousity to check one plug, I would check them all. Each cylinder can and does have its own characteristics. So, while by the luck of the draw, the single plug you check might be fine, the very next in line could show signs mal-peformance.... lean, rich, oil control, etc..

My 2 cents.

And I would also like to extend my thanks to RM... that pdf is a ton better than the illustration I've been using in my many Haynes manuals.


`68 280sl
`62 Lincoln Continental Conv.
`73 450sl