Originally Posted by
earlwb
The new gasolines have little to no residue deposits on the spark plugs or combustion chamber and valves for that matter. One of the frustrating things is you can't effectively use the spark plug insulator color as a gauge for if the engine is too lean or rich, like we used to do with the old leaded gasolines. Usually you can pull a plug out at 50,000 miles and it doesn't look like it had any wear on it at all, or very little wear, and the electrode looks clean with little to no color to it. Thus the spark plugs don't foul like they used to, unless the engine has bad rings and starts using oil and smoking.
Yes, this is quite true. Especially with a four stroke engine, but also problematic with a two stroke. A plug that comes out of a four stroke engine dead white is not necessarily way lean as would have been the case before. I've seen that a lot. It does make tuning difficult at times, especially on custom, or street/strip hot rod applications where you have changed things and need to custom tune. One of these days I'll buy a wide band O2 sensor setup for tuning. I just don't do enough of the high performance work anymore to justify the high cost of those wideband systems. But it sure would be handy for my own projects....
AV8TOR