I can hit mid to high 14's once and awhile on the freeway doing 65-70 with a very light foot and premium, no head wind, and light load. I have 97' F350, standard cab, longbed, zf 5spd... no major engine mods.

 

Once again EFI does not count. We are talkin' carbed engines.

 

A guy over at www.bobistheoilguy.com posted some pics of his piston tops, cylinders and combustion chambers after he had done this:

Step 1: Added to 20 gallons of gas was 1 quart of Marvel Mystery Oil and 2 quarts of ATF.

Step 2: After finishing off the first tank, he ran 1 quart of Marvel Mystery Oil in with 20 gallons of gas.

This was in a Chrysler minivan which has 170,000 miles on it.

Everything looked as clean as a whistle and his van ran a lot better, but he ended up having to change the water pump, and as long as he had everything apart, he pulled the heads just to take a peek, which is how he came up with the pics.

Anyway, I decided to try his little procedure on my '83 F250HD 4x4 with a 460, 4.10's, a C-6 and a carb. It has approx. 99,000 miles on it. Original engine.

Before I did the procedure, I was usually getting mileage in the 7's, and sometimes into the 6's, and once or twice as high as 8.25. After the first step, I filled up the front tank (the one that had both MMO and ATF in it) and checked my mileage, and it was 8.59, the highest I'd ever gotten. Funny thing is, I was flooring it around, climbing steep long grades, driving fast on the highway, etc. during this tank, yet it got its best mileage.

It runs smoother now, too.

After the second tank, my mileage came in at 8.09, because I did more in-town driving. Now the truck runs great, idling very smoothly.

What I'm doing now is running a bottle of Auto-Rx in the oil to clean out the inside of the engine. I'll let you know what I find about that after THAT procedure is done... it lasts 1500 miles for the cleaning phase, and then I change the oil and filter and enter the 2000 mile rinse phase. Then, I'm gonna repeat the whole Auto-Rx process one more time (which is what they recommend for vehicles with over 100,000 miles on them).

Fun stuff! The reason I'm mentioning it in this thread is because we're talking about improving mileage. I know I'll never get to 15, but if I can get to 9 I'll be happy.

 

Like most others, my 1996 F-250 with 460 4X4 and OD automatic and 4:10 rear end will get 11 on highway at 65-70 unloaded. Best effort. Towing a 24-foot RV and a racing boat behind that it gets 7.5-8..which ain't really bad since it will go anywhere and pull anything.


Dan

 

Don't be a dick bear... there is no mention of him only wondering about carb'd engines.... forgive us all for trying to add information to a public discussion. I always thought more information was better but I guess when you have old age and treachery there's no room for extra knowledge....

 

My 86 dually started out at 8 MPG no matter what. Drilled out some perferatred plates increased milage to 10 MPG no matter what. Now I have added a 5 speed ZF and am getting 12 MPG no matter what. Should mention I tow a 12,000 lb boat and trailer.

 

What does this refer to?

 

I have factory exhaust on my 86. After my first trip towing the boat I got home at dark used 1 tank of gas. For some reason I decided to look up the 3 1/4" tail pipe. There was something in there. Got my flashlight looked up the pipe again there was a perforated plate in there. At best this left like a 40% open area. Drilled it out with a 3" hole saw. Looked up the pipe again there was another perferated plate ... drilled that out. Next trip and back to the same place took 3/4 of a tank after removing the plates.

Before I am done I will be getting close to 20 MPG with this rig. Have done as well as 25 MPG back in the mid 70s with a 460 dually haulling a race car. the truck turned 11.46 in the quarter mile becides. I only expect close to 20 these days with the reformulated gas in the summer. I would expect a bit less in the winter.

 

You are VERY naughty for making these claims!

With regard to the perforated plates, now that you describe them, my Dad had them on his '88 E350 (460) and I did the same as you and cut them out with a hole saw. It did make a tangible difference!

 

Spastic, two things, premium reduces gas mileage on an engine that will run on regular, and you have got to chill out, im sure theres someone interested in efi engines who reads this, thats great, but the main point of this is carburated engines, bear recongnized that and stated his opinion on it, thats no reason to call him a dick.

 

I prefer the term "Richard Cranium" It is much less offensive. I personally prefer to hear about the EFI engines also, because it helps me to find out if I am making my OWN engine more efficient. If I can get my set up to run close to the same a that of an EFI, I think I am tuning pretty darn good.

 

Not being a dick, He has a carbed engine and the cost to up grade to an EFI would be what his truck is worth, so EFI specs don't help him at all. In fact you are being the dick because you don't seem to care if the guys give him apples and orange comparisions.

 

This was the original thread. Nothing about Carb. or EFI. EFI came out in late 87. I have had both efi and carb 460's and had almost the exact same mileage. It doesn't make any sense to to limit this thread to just carbs.

 

That's excellent. Such individuals suffer from a condition called (in medical terms) rectal occularity, aka. a crappy outlook on life.

This doesn't apply to anyone posting in this thread, IMHO.

 

LMAO!! I LOVE IT!!! Thats great!!! I'll keep it in mind for the future!