[Jesmol]

I replaced my spark plugs yesterday (changed from NGK to Bosch super 4's) and noticed that the front 3 cylinders had a reddish residue all over the are within the combustion chamber. The back 3 cylinders had a greyish colour, with a very smell amount of red material.
Never seen anything like this before. Anbody got any clues??

btw I run mostly on LPG, with about 1/2 running on Petrol (std unleaded) every 2000Km. Gas system is an Impco, and I have a pod air cleaner sitting behind the Headlights. Car is a 95 XG XR6 with about 130,000K, and the headgasket has been replaced about 5000K ago for the second time.
Driving style is not agressive, and mostly country driving cruising between 110 and 140.

 

[lsd0]

My ED fairmont is also on gas and the spark plugs seem to be covered by the same reddish deposit you are talking about. What the hell is it?

 

[Aussiblue]

I'd suspect an upper cylinder head lubricant something like (and perhaps even) Red-X. The same thing happens when In I add Red-X to my normal fuel car and I suspect a gas powered car might need something like that.

 

[Jimbo]

..... noticed that the front 3 cylinders had a reddish residue all over the are within the combustion chamber. The back 3 cylinders had a greyish colour, with a very smell amount of red material.
Never seen anything like this before. Anbody got any clues??

I've seen this on some taxi's running on LPG. It sounds like you might be suffering from a bit of valve recession (this can happen on gas) The red deposit is probably small (minute) bits of iron oxide (rust) from the erosion of the valves and their seats. Check (and keep track of) your tappet clearances to see what's happening, they'll close up with recession.

The only reason I can think that it's different from your front and rear cylinders is that the mixture might be different from the front to the rear and some cylinders are running hotter.

 

[Jesmol]

Thinking about this, I've had a thought (frightening but true).
Doesn't LPG have a dye added to it so that leaks can be seen, if thats the case, the front three cylinders may be running cooler, and not burning the dye off???

To all others running gas, what sort of consumption figures do you get?