I have a Mogas STC and have ethanol-free 93-octane mogas available locally, but have heard from some people that mogas will gum things up and is just generally a bad idea... But I've also heard that the lead in Avgas can also cause cylinder problems. Other than fouled spark plugs I hadn't heard of lead being a concern for a Lycoming O290. Am now wondering if Avgas is part of the reason two cylinders had slightly low compressions recently (with leakage into the exhaust), as I've been using more Avgas than Mogas lately while the previous owner used mostly Mogas (low time engine overhauled ~ 5years ago). Is it the lead burning causing buildup on the valve face? Buildup on the valve stem guide, causing asymmetry in seating and then the valve face issue? Other than simply geometrical tolerances being too loose or poor baffling causing a cylinder to run too hot, what else could cause low compression to develop?
Starting to hear all sorts of 'old wives tales' about Avblend and Marvel Mystery oil and all sorts of other things 'fixing' low compressions, none of which I trust. Looking for any technical advice on these issues, and especially whether Avgas or Mogas is a better choice.
Starting to hear all sorts of 'old wives tales' about Avblend and Marvel Mystery oil and all sorts of other things 'fixing' low compressions, none of which I trust. Looking for any technical advice on these issues, and especially whether Avgas or Mogas is a better choice.