I just bought a 1998 F-150 SuperCab 4.6L 4x4 this past Friday, and it seems to be getting 18-19mpg so far.

But, I'm wanting to have dual exhaust put on.

I've ALWAYS heard that the less back pressure there is, the more mpg you'll get. But, is this correct?

I'm not hard on the truck at all. Unless I have to make a quick judgement or change while driving, I don't get it above 2,500 rpm, unless I'm towing.

What I thought about doing was dropping the factory exhaust system from the back of the last cat, then having the muffler shop run either 2.5" or 3.0" pipes from a y-pipe of the same size, and split them with tips at each corner of the rear bumper.

Now, will this fully-straight pipe setup be BEST for fuel mileage, or will a performance muffler or cat-back be better?

BTW, I also plan on purchasing a programmer and cold-air intake kit in the near future.

Thanks for any suggestions!

Nightrain

 

It should be ok. You still have the cats to provide enough backpressure that you won't lose any torque.

 

You think the fuel mileage might increase a tad, if I can keep my foot out of it?

Nightrain

 

A little. Mine did when I installed my Flowmaster cat-back system.
My Diablosport Predator helped the most with power and mileage.

 

The Diablosport Predator is a great recommendation, which tune do you use?

Check out our selection here at the Motorhaven shop for mod products and info, we are a forum sponsor and the FTEDEAL promo code gives forum members $20 bucks off orders for most brands we carry.

Here's the list that I'd jump on for your F150:

Diablosport Predator - http://motorhaven.autoanything.com/performance-chips/60A1907A0A0.aspx?kc=MOTORH

Magnaflow Cat-Back system - http://motorhaven.autoanything.com/exhausts-mufflers/20A50221A1.aspx?kc=MOTORH

Volant intake - http://motorhaven.autoanything.com/air-intakes/60A1817A0A0.aspx?kc=MOTORH

 

I use the 93 octane for 2 reasons
1) MORE POWER
2) The increase in gas mileage per tank is greater the the 20 cents more per gallon for the extra octane. I'll give .20 for an extra 1.5mpg around town and about 2mpg on the highway.

 

I've tried many times to explain this to people, using spreadsheets to calculate the fuel cost per mile of 87, 89 and 93 octane. Most people look at me like I a speaking martian!

 

Well, it works for me and I'm sticking with it.

Take me to your leader