I had some engine knock at the factory timing of 12 with regular gas, but goes away when premium is added. Spark plugs looked hot. I tried retarding the timing to 10 degrees but fuel mileage dropped from 37 in the city to 30 and from 45 on the highway to 40. So the plan is to run premium fuel and advance the timing as much as possible to get the best mpg theoretically.

Jeff

 

You may have bought some bad gas. Try a different gas station.

Get back on regular gas. Generally, there is no benefit to running premium gas, just more expense. Set the ignition timing to spec --align red mark on crank pulley with pointer while the service connector is jumped.

Any CEL codes? When did you do the last ignition system tune up? Have you cleaned the EGR valve, chamber, and ports?

 

Already tried a couple of tanks of fuel.

If you read the post, you would understand why I cannot run 12 degrees with regular fuel. I don't need a lesson on setting timing, just wanted to know how much timing can be run with premium fuel. I changed entire ignition system recently, but it was pinging before it as well. EGR is clean.

NO CEL

 

he read the post. so did i. you can go pound sand with that 'tude.

the fact that you can't run factory timing without knock is an issue that needs to be addressed before you come up with goals of running premium fuel with some sort of advanced timing curve.

no matter what you think or what you do, the initial issue is going to impede your ability to do anything that involves optimization and fuel mileage.

i would suggest a few things but it is apparent you don't want any suggestions on how to solve your baseline problem.

good luck.

 

are you sure you dont need a valve adjustment?

 

I just checked all the valves and they were good. Everything seems to check out on the motor. Maybe the fuel injectors are dirty. Not sure what would cause the pinging between 1500-2000 rpms.