I just had a question for the more mechanical savvy individuals here. I am in a discussion on the
facebook Crossfire page and a guy maintains that prolonged use of 87 octane gasoline will plug up and ruin the catalytic converters. Of course I maintain that it will not but only cause the computer to adjust for it and you would have a little less horsepower. I looked through my service manual and all I could find was that contaminated gas, oil and antifreeze would cause it damage. He said that replacing converters is what he does so of course he is right. It all started because some one put 5 gallons of 87 octane in the tank and wanted to know what to do about it. Any thoughts? Thanks

 

We have had people run their car on 87 for extended periods of time they reported no problem. That proves nothing but I would say that if the engine knocked too much and the ignition could not counteract it then damage may occur to the engine only. Too much sulfur in the fuel, or lead would damage the cats. The CE light comes on in some cases of a risk to the cats occurring.
Five gallons would not cause any damage, I am sure lots of us have had the wrong fuel from the tanks at gas stations.
Mid grades are often blends from two tanks at the pumps and equipment fails.
My vote says no problem.

 

He was trying to convince me that lower octane gas would carbon up the catalytic converter.

 

Excessive detonation could damage the cylinders but 87 PON Unleaded should not bother the cats at all.

My Jeep 3.6 v6 turns 6400 rpm with higher compression than the XF and produces 290 hp all on 87 PON.

The question is whether the computer can retard the timing far enough for 87 PON but I have not seen any good reason for the 91 octane requirement.

 

I also agree based on common sense, but not on actual knowledge. 5 gallons of leaded gas will do nothing, 50, 500 maybe. The only real threat would be to damage from pinging/pre-ignition/detonation IF that even would happen out side of what the computer would compensate for. So real world worst case, no issue, possibly MORE horsepower if no pinging and better mileage, since the lower the octane, the higher energy in the fuel. (a fact that is hard for many people to grasp)