Date registered: Oct 2004
Vehicle: 2010 S550
Location: Tampa, Florida
Mentioned: 13 Post(s)
Quoted: 232 Post(s)
RE: Why I like my CEL
I'm glad you have recalled the term non sequitur. It just doesn't follow from my post.[:)] Pun intended.
A common cause of a Check Engine Light (CEL), especially one that is intermittent, is low octane fuel. Low octane fuel may not cause recognizable driveability problems, but could illuminate the CEL.
You said you didn't experience driveability problems, so it is likely not from water in the gasoline (especially some that may be trapped in the fuel filter) - another common cause.
Both of the foregoing have occurred in my wife's cars, resulting in Check Engine Light illumination.
You speculated yourself that the fuel mileages you experienced may be the computer inaccurately sensing what is going on - you did not say whether your fuel readings were manually calculated, or shown by the vehicle's trip computer. That leaves the question a bit open.
Leaving the abbreviation "CEL" unexplained on first use is very little different from teenies and their nearly unintelligible short message service typing styles seen in some postings (that I routinely ignore, because I would like people to communicate clearly when they ask for assistance) - eh, WOT?
2005 S500 4-Matic