is it bad to run premium gas?

Premium gas is not "better" than regular gas. Premium burns at a slower rate (less easily). It's meant to be used in a higher compression engine. It has to do with ignition timing and other things that you don't understand. Premium also does not "clean out" an engine. Use what the manufacturer recommends. What's so difficult about that? Premium gas has something in it that a regular gas engine can't make use of. Premium has more octane and less heptane than regular. So the extra cost is a waste.

For all the car experts that think they know what octane is, but never heard of heptane, read this and learn:

http://science.howstuffworks.com/gasoline3.htm

Yes.

The higher the octane, the harder it is to ignite. This is great with a high performance engine. For most engines, it is not only a waste, but it can also do damage.

You will put the unburnt fuel into your catalytic converter. Normally, a little goes there to be burned off, but now, you are putting in much more than it is designed to do. This will cause it to get hotter and break down sooner.

Also, computers can adjust the timing for this, but, this will actually cause a reduction in performance.

Use the octane that the manufacturer recommends, unless you have done major modifications.

Not necessarily bad, just a waste of money. Your town car with a stock engine is designed for regular gas. Higher octane gas is a waste of money and your engine may actually get worse mileage with the higher octane gas.

Higher octane gas is NOT better gas, it is the SAME gas with more octane in it. Octane just keeps higher compression engines from knocking. That's all. If you engine doesn't need higher octane gas, and your Lincoln Town Car doesn't, then you are wasting your money buying it.

Try a tank-full before an extended high speed trip to see of the mileage improves. Your motor has a knock sensor which in the end reduces ignition timing costing fuel economy and horsepower when 87 octane fuel is used. The higher the octane of the fuel, the cooler and slower the fuel air mixture burns to prevent pre-ignition. You will have to be the person to decide weather or not the extra cost of the fuel is worth better fuel economy if any!

Lanab is correct. Running a higher than specified octane level is fine but lower than required can destroy an engine due to pinging ( or pre-detonation ).

Only for your wallet, There is no effect on the car (good OR bad) from running higher octane than specified.

Running a lower octane can damage an engine, but not the other way around.

Yes.

The higher the octane, the harder it is to ignite. This is great with a high performance engine. For most engines, it is not only a waste, but it can also do damage.

All injected cars feature an IDLE AIR CONTROL VALVE that fine tunes and adjusts AIR/FUEL mixtures around town and under LOW speeds! Most of these things get clogged up over time and require CLEANING UP! NEWER FUELS are now EURO type fuels meaning they are LOW SULFUR fuels! his changes how fuel is burned in ALL grades of fuel out there! OLDER CARS using premium HIGH SULFUR FUELS may run PERFECTLY with our newer fuel types. YOU can figure this out if you watch your Mileage over time! Keeping YOUR IAC VALVE SHOWROOM CLEAN, is the best insurance of LONGE engine running! Here the AIR portion of injection is called into play, the OVERLOOKED part of things! INJECTORS all come from BOSCH, and they NEVER go bad anymore! It is the AIR side that jams up over time from cheap oil changes, SLUDGE and GRUNGE build-up! I am a FANATIC for clean engines and was trained in on DOMESTICS first and EURO CARS next! TRUST ME and keep that IAC clean and save on CONVERTERS and SLUDGING OVER! BYE NOW!

For your car, regular gas is fine. You are running the SOHC 4.6L V8 engine and regular is all it needs. The only exception is the DOHC 4.6L 32 valve V8 which is found in the Marauders.

No it's not bad.

Your car may run a bit better, or not.

Newer cars with computerized systems re-tune themselves as they run.

Older carbureted cars would run better on one or the other - as long as it was tuned for it.

I ran premium in my old cars (and I tuned for it). When the wife put low grade in, it ran like crap and stalled.....no power.

I could have tuned for low grade......but I liked my stuff the way I liked it.

Her car was tuned for lawnmower gas......as she liked it.

Your car will make up it's own mind for you.