I have a 5.7 volvo gsi, fuel injected engine, throttle body injection. It appears to run perfectly, goes right up to redline, very smooth, perfect compression,no obvious problem except my fuel economy is getting very poor. It should be about 2.5/gallon or slightly more and is now less than 2 and dropping. Plugs are sooty black(not oily) and the discharge water dripping over the prop leaves a black deposit when running on the trailer. ECM is recording no errors. The engine manual calls for 93 octane. I burn 90 octane, no alcohol, raised to 92+ with octane booster and have since buying the boat. I'm considering replacing the injectors and, if that doesn't work, trying ethanol 93 octane.
Anybody have any ideas?
Anybody have any ideas?