Whats gas to use for lincoln ls?

Your car has what is referred to as Hall effect timing. The on board computer (ECU) will advance or retard the engine timing and piston firing according to the presence of preignition or detonation, usually based upon fuel octane levels. If you use 91, the car will likely run okay. If you use 93, then the timing can advance by the computer and you will get better fuel mileage and slightly better performance. On my Mercury with the 4.6L, I gain almost 4 miles per gallon with 93 octane fuel, and I usually average 28 mpg highway. One other thing is that your car has an idle air control valve that may not set off a "check engine" (sensor) light if it malfunctions. Often, at around 50 to 60 thousand miles, these show problems with carbon buildup and they do not clean well, so replacement is usually the best bet. Also, make sure that your filters are all clean, as a clogged fuel filter may also cause you some sputtering, as well as water in the fuel from condensation buildup in the tank (both your fuel tank and the ones at the petrol stations).

The LS uses regular unleaded.The fuel is not the cause of the sputtering. The computer is programmed for regular unleaded. Look for other causes. Vacuum leaks are especially suspect on this engine. The PCV hose is known to leak. Check the MAF sensor for contamination.

Lincoln LS are rated for 91 octane. Check your owner's manual to see the proper octane to be used.