Originally Posted by 3050rpm
1) Is 89 mid-grade the wrong stuff to use on a regular basis?
2) How well does the knock sensor compensate for lower grade gas?
3) Does the onset of summer weather, and the seasonal formulation of gasoline, have an effect here?
4) With high mileage on an otherwise well maintained engine (200,000+ miles) is carbon buildup inevitable, calling for higher octane fuel?
5) Might I be hearing something other than knocking (like the marbles in my head for instance)
#1. "mid grade" fuel is ok to use, provided you're not towing anything
#2. knock sensors work great - on everything EXCEPT carbon buildup
#3. Summer does have an effect, when warmer the fuel expands at a different rate (generally slower)
#4. carbon buildup is a long term effect on ALL engines - a good dose of Sea Foam & STP fuel treatment then a fuel filter change should make a major difference in it's drivability.
#5. the marbles issue sounds like pinging because of carbon.