LilRoush

Placard for PSI is for factory equipped tires. What type/size tires do you have on it now? Most of today's tires like 32-34 psi for street use.

As for the MPGs, look at rolling resistance. Old cars wear out bearings and brake calipers. Jack up the car and spin the wheels. Make sure the brakes aren't dragging and the bearings let them spin freely. Also check your alignment. Poor alignment can kill fuel economy.

BabyGT

Thank you! I've been arguing this for years. Different brand and model tires have different psi ratings. The closer you can SAFELY get to the max pressure the better mpg.

You're not gonna inflate new tires on a 60's era car based on what psi the factory tires used. Or how bout a rat rod car like a t-bucket? They certainly ran a much different psi from the factory than the new street tires your slapping on it.

PNYXPRESS

You should NEVER inflate to what the max is! The placard isn't for "factory tires" it's for factory size tires. Doesn't matter the brand as ford didn't design the psi around a certain tire brand. Ford uses what ever tire is cheapest for that particular size.

This is why the 05-09 gt cars came with either Pirelli tires or bf Goodrich tires depending on which year the cars were built and when they bought the supply of tires.

Daehawk

My tires are rated at 44psi. Today I had been getting bad gas mileage and checked them for the heck of it...

back right - 32
front right - 25
front left - 20
back left 30

Needless to say it felt like a different car when I aired them all to about 36/37 or close.

BabyGT

I clearly specified as close to max as safely possible. I did not say AT max psi. And they placard is individual to each car. It wouldn't be that hard to change the psi rating on the placard for different tires used for that year. They have to change the vin number on EVERY tag.

I didn't give an exact number cause tires are all different from brand and model, the only way your going to have the same psi is two of the same brand/model tires.

LilRoush

Many tires of the same size use the same psi. However, The 15" 'stock' all season tires on the V6 wouldn't like running the same psi as I run on my 18" 'performance' tires.

That is why all tires have a max psi right on them. They vary by tire.

iateadonut

After the tire pressure and new spark plug wires, I got about 16-18 mpg for "city" driving. I'll have a chance to do some highway driving this week - will post again after I use the 10 gallons I filled it up with but it looks like I'm pretty good here.

The sulfur (burnt hair smell is more like it) has more or less subsided, so I guess tuning it up has fixed it up enough that the computer has re-configured (and it wasn't a bad cat after all).

I put in V-Power NGK spark plugs when I tuned up. Should I be using something else? (On my Grand Am, a switch to Laser Iridium increased gas mileage from 16 to about 20 city.)

Mobiusone stang

16-18 is what i normally get with hard city driving. I usually average 20-21 mpg on highway driving (normal big city Houston traffic included) which sucks. Normally out of a full tank I can get about 280 miles till it is dry. Which sucks. But these v6's had less power than the v8 and still had to haul the same amount of weight, that is why there isnt a big difference in MPG between the new edge v6 and v8

TfcCDR

Sorry to join this so late, but:

1) Overinflated tires LOSE TRACTION. That can cost you mileage and reduce steering authority. If you're not seeing even wear across the tread of the tire, you're not properly inflated.

2) Placard tire pressure is by tire size and rating, not manufacturer, tread, etc. The idea is that a particular size of tire will have a particular set of characteristics at a particular pressure.