I'm very happy with the 4.6 here. It does everything I ask it to do without complaining.

I've enclosed my mileage chart below. I drive a mix of city and highway and I don't anything special to save gas other than use the cruise control when I am on the highway.

It doesn't like 87 or 89 octane BP gas. I have to run any other brand at 89 octane or it pings a little bit under load at low RPMs. Other than that it is perfect.

 

I have the 4.6 in a reg cab long bed 4x4 and the only reason i have the truck is to load it heavy and work it hard. I get tired of people who have to have all this power and not ever need it all. Does anyone remember trucks from yesteryear that did not have power even comparible to our and they seemed alright. If the 4.6 is a car engine than the 5.4 must be also because they are very similar both being in the modular family. From the majority of the posts on this site it does seem that the 4.6 does get better fuel mileage compared to most 5.4 but not by much. The 4.6 has plenty of power for most everything but the choice is yours.

 

From reading the engine specs in the 08 brochure with the new mileage ratings, the 4.6 is one mpg better in the city and two mpg better on the fwy - 2WD. What's interesting is that the 4X4, regardless of which V8, is rated the same -13/17, the same as a 2WD 5.4 V8. The 4.2 V6 is rated the same as the 4.6 - 14/19 with the manual tranny V6 only one mpg better on the fwy. So, not much difference in mpg between engines and drivetrain with the new mileage charts.

Hope that clears things up

BTW: I have the 5.4 but got the truck for the 4X4, not the engine.

 

Xyzzy - Great job of record keeping. Surprised your 4.6 pings on BP gas. I run 89 octane BP in my 4.6 exclusively and it runs fine. Perhaps you need a slight timing adjustment?

 

BP is probably the most popular gas where I live. I had an 07 4.2L earlier this year that pinged too, but putting in a set of colder plugs fixed that.

In both cases the ping is/was very mild. I wish I could adjust the timing but it's all run by the computer.

I'm tempted to put in a set of colder plugs in the 4.6L since doing that worked real well on the 4.2L.

4.2L story: https://www.ford-trucks.com/forums/616367-octane.html

 

Ok, let me digest this a little, Ok, I have a 97 with the 4.2 auto 2wd bought new the sticker said 18 to 22 MPG, best ever was 14.5 avg. It avg.12 mpg, I work it like a dog but keep the maint. up on it. Today I will be picking up a 2005 F150 4x4 auto with the 5.4 just broke 50,000 miles, but like new in every sence of the word. List for 22,879 I am paying 17,450. Tow package, the works. The dealer said I should expect to avg. about 17 MPG, that is what he has seen and the feedback from customers he has. I never knew anything about a "plug" issue, to be honest I haven't been on the site in a while. ( I know my fault ) anyway, when I got my 97 my mom got one the sameday but she got the 4.6 The 4.2 in 97 was listed at 205 hp and the 4.6 at 215 but the 4.2 was listed with better gas milage. WRONG, she had more power and better milage. Why? could it have been I have to over compensate for the lack of power?
I love my old truck and I am going to keep it just time to upgrade and this time I am getting the bigger plant.
Thanks for listening, good luck with your quest and remember doesn't matter what you buy as long as it's a FORD! Oh, by the way, the 97 4.2 ping's like crazy on low test BP.

 

Since the NGK TR6 plugs worked so well on the 4.2L I popped in a set in the 4.6L today. I was pleasantly surprised at how easy changing the plugs ended up being. All I had to do was loosen the fuel rails and remove the brace on the driver's side bank. I gapped them at .045 instead of .054 to see what would happen. The stock plugs were Motorcraft AGSF32N.

So far the truck drives a bit smoother but that could all be in my head. I'll give the truck a good workout and report back.

 

I decided to go a step further and go with a "7" series NGK, so I installed a set of TR7IX (3690) plugs a few days ago. So far there have been no misfires or any weird effects and the pinging is totally gone on 89 octane. I am adding in 87 octane right now (2 partial tanks) so I am probably pretty close to 87 octane in the tank and it pings maybe just a little bit under only the most extreme lugging scenarios. The plugs cost around $65 shipped.

The last tank was a trip today at a constant 55-65mph. I've never gotten mileage that good before. I don't know if it has anything to do with the plugs.

I'm not worried with plugs these cold under highway or towing use but I am watching carefully to see if they load up during extended idle periods or on cold startups. So far so good.

The TR6 plugs ended up with around 1000 miles on them. They looked fine although if pressed I'd say they looked like they had been run just a little lean to me.

I've got plug changes down to about 45 minutes now, and that is with torquing them properly.

I gapped the TR7IX plugs at .045. They came at .035 and NGK recommends that you don't deviate more than .008 either way, but my gap tool has a .040 and a .045 so what can I say?

 

I test drove an 08 with 4.6. I have had the 3v 5.4 since 2004. The 4.6 seems gutless after driving the 5.4 for awhile.

 

Zyzzy,


are the "7" NGK's a hotter or colder plug?

I am very interested in this as the "gutless pig" is starting to get close to needing her tune-up and I am thinking to buy the parts and have them there waiting before I decide to slop the old pig.

Thanks for the detailed info btw. Alot of folks on here appreciate it!

D

 

Two steps colder than stock.

 

Xyzzy, got one other question for you...

Do you have an edge? I can't remember if you had said you did or not.

I had some problems myself with a few gas stations around here in Texas...getting gas that was making the engine ping. I am guessing mebbe that it was due to the Ethanol increase that occured. I didn't want to go overboard, so I just dialed back my ignition a half degree and it ended the ping at high RPM at once AND didn't hamper the performance in a noticeable manner. I have also played around with the RPM to shift points a bit and by just being a bit careful but still keeping my speeds at about 75 MPH I can get, according to both the Edge and my fuel usage at the pump, on the freeway, an honest 18 mpg. Adjusting the rpm-shift points, I can keep the tranny from downshifting too rapidly on overpasses and ESPECIALLY in the hillcountry around Austin. I cannot be more pleased with the effects so far. I am VERY curious as to what I can get out of it after the tune-up in the future.

D

 

No.
You can adjust the timing with a tuner? And the shift points?

I'd love to dial back the timing a bit and I'd really like to have the OD kick in at a higher speed than it does now, and stay there on moderate inclines, but a tuner seems so complicated and expensive.

Is there a cheaper way to adjust the timing?

I suppose I am adjusting it a bit with colder plugs but $65 isn't cheap really.

I wouldn't mind losing a little power, I just want the engine to run real smooth with no pinging, ever. When I tow I lock out the OD so I have plenty of power to spare right now.

 

You can with most, IIRC. The Edge is the only one I have experience with, though. The owners manual has everything in it. You can download it off their website and you can read about what all it can do.

It took me almost a year before I was comfortable with it...but hey, I am a coward when it comes to my gutless pig. I like being able to set up the specific program on my laptop. VERY nice option.

Not that I know of, bro.

Thanks again for the plug tips, though. I am going to get some of those NGK's ASAP.

D

 

I have a 2005 4.6 STX and for what I use it for it is plenty. As far as mileage, my last fill was 13 mpg and it is -8F and most of this last tank was in zero or colder weather. The best I have ever got is 19.6 mpg on a nice summer trip of 600 miles round trip with a fresh oil change. My brother's F250 with the 5.4 gets about 10 mpg in below zero and during the summer the best he has gotten is 18.7 mpg