The manual says use premium, but that regular can be used without
damaging the engine.  That's what the manual for my 94 says, anyway.

I'd think you could easily go to the dealer and ask to see a manual.  I
never buy a car without reading the owner's manual, just to see about
things like that.

The Lincoln Town Cars have always used "regular" unleaded. The issue with
the LS430 is now you're getting a high performance engine with advanced
ignition timing and a higher compression ratio.

Penny-wise and pound foolish; stepping over dollars to pick up dimes. If
you cannot afford the small percentage difference in the price of the
gasoline, you sure as hell can't afford the car! There's a difference
between frugality and stupidity.

and yes, you -can- put 87 octane regular in the tank, but I sure wouldn't
and IMO only a schmuck would. The dealer will tell you "only in an
emergency". The newer engines can automatically adjust (retard) the
ignition timing so you won't experience any damage from spark knock, but
engine performace will sure suffer.

I have a better answer than all of you, but it requires a little more work.
I put in 1 part 87 octane to 1 part 93 octane...and tilt the mix to get
about 91 octane which is what the car requires. I can tell from looking at
any point on the gas gauge how many gallons needed to fill up (this took a
some time and experimentation). I usually fill at half tank where it needs
11 gallons to fil. I'll put in 6 gallons of 93 octane then the balance of 87
octane. It requires two different credit cards at the pump, too, because
most pumps will not work the second time if you use the same credit
card...the pump thinks something is wrong. And if you use cash, you have to
fill, pay, then fill and pay again (so I don't use cash).

One response here said if you can't afford the fine fuel you can't afford
the fine car. My approach is different: It's being value-conscious like this
that allows me to afford the fine car!

Every time someone posts a question about octane, a war of wits ensues (and
typically, the combatants are unarmed).

The engine will not be damaged by using 87 octane.  I drive a 2004 LS430 (my
5th LS400-series car), and it does not mind 87 octane fuel.  Maybe I'm a
"schmuck" for using regular, but seeing as it makes absolutely NO DIFFERENCE
to the car, the driver, or anyone else on the face of the planet, I figure
I'll use the extra money to get a high grade Starbucks.

A few more points ...

The performance will be reduced by an amount so small, that I defy anyone
under normal driving conditions, without a dynamometer connected to the car,
to tell the difference.  My car still kicks most cars butts on the highway,
on the streets, and anywhere else they care to challenge.  Believe me, 290
horses, or 285 horses really don't make a hill of beans of difference.

You will save approximate 20 cents per gallon or roughly $400 per year if
you drive around 800 miles per week.  If the $8/week makes a difference to
you, then buy the regular.  If not, buy the premium.  It really really
really really doesn't matter.

Your milage will be slightly less if you use regular, but again, so small a
difference that it would surely be overcome by one or two lead foot
jackrabbit stoplight starts, and the 20 cents/gallon more than makes up for
the small difference.

Unless all you're trying to do is create another endless spout of drivel on
octane this, and horsepower that, your question has a simple answer.  The
car does NOT need premium, so do what makes you feel good.

Good night Gracie.
Carl

Read the manual that comes with the car.  Then read the WARRANTY.  Most
warranties will be VOIDED if you don't use the fuel (octane) prescribed
for your car.  If you have engine problems that are in any way related
to the fuel system..........you will be on your own.  The warranty will
not cover it.