the 8-6-4 or 6.0 or 368 motor is a dependable low power motor.. The best gas mileage I ever got on the highway was 19mpg...But let me say that was with the 8-6-4 disconnected, thats running on all 8 all the time... around town 15 at best... but that was years ago...
He means that the dealership disable the cylinder deactivation feature (when customers complained that 6 cyl mode was vibrating) two ways. One (like my car), they cut the orange wire that sends the high gear signal to the computer that the trans is in 3rd; or, by actually swapping in a different computer that does away with the deactivation. Check under the car first.
Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
Re: 81 fleetwood brougham
If the wire is cut, run the wire thru a toggle switch. Mount the switch at the bottom of the dash. Switch off until you reach freeway speed then flip the switch to engage 4 cyl. mode. The only thing problematic is the plastic valve covers tended to crack if the owner or mechanic was not careful replacing the gaskets.