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Discussion Starter #1
Alright first I'm on a cell and the site doesn't let me search.

I've got a late 99 f250. All I've done so far is
4" exhaust (stainless duals)
4" lift & dual stabilizer
18x10's w/ 325-60-18 maxxis bighorns

Planning on an AFE stage 2 and chip/tuner.

Haven't been able to get a good read on mpg yet since I just put everything on. I know with winter mix I'm only around 12-14 before everything.


Suggestions on what else I can look into to improve mileage?
 

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Discussion Starter #3
Only real difference between stock to them is width. They are only a little taller. Overall it's more weight from the tires only the wheels are lighter.
 

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Loose the lift too. Too much bad air under the vehicle will reduce MPG...happened on my bus when I put taller tires on to change the overall drive ratio to increase mileage...I lost MPG.
 

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Ok as I said lift and tires just put on. Clearly they aren't coming off. I am looking for reasonable suggestions

Tires are 1.8" taller and 2.6" wider not a drastic difference.

Mileage is with winter mix. NOT calculated with lift/tires yet. So far no change yet
 

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-Most say that doing an EGR delete gained them a MPG or two. I have yet to try it so I can't say one way or the other.
-Easy on the throttle obviously.
-If you have a boost gauge, many recommend trying to keep your boost in single digits and below 5 PSI for max mileage.
-Some tuners offer mileage settings, but again YMMV. I have read of folks who used the mileage setting and then the base level for performance and got better mileage on the performance setting.
-Keep tires inflated to proper settings. With stock that would be what the sticker in the door jamb says, but with those I would say ask what the pros would run them at.
-Anything to make the engine run more efficient...so making sure fuel and air filters are clean and in good condition, as well as ensuring you have ample fuel pressure would help. And I would also bet that if you have obstructed flow through your CAC (lots of dead bugs, a winter block off, etc) would impact the final charge temp. From what I understand, cooler temps equal better efficiency/power. To go along with this, most of these engines' CCV systems wind up putting oil throughout the CAC and CAC pipes. I'd be willing to bet that an aluminum CAC coated with oil on the inside does not cool down the air charge as well as a clean CAC.
-Reduce your drag. You lifted it and so hopefully understood that lifting was going to have some negative effect on mileage. But, you can help get some of that back by lining the bottom of your truck in some way. If you can reduce the turbulence under the truck you will increase mileage.
If it's a pickup and not an Ex, my personal experience, and from what I have read it's many others' experiences as well, leaving the tailgate up is actually better than putting it down...and of course having a bed cover helps as well.

All out of ideas. Hope one of em works for you!
 

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Have you read the stickies? They are still 100% valid.

How serious are you about MPG? How much do you drive a year? I drive mine a lot and thus can justify darned near any modification for MPG. If your truck is a weekend toy - don't bother.

Business or personal-only?
Loaded or empty as a % of mileage?
Towing?

By and large, improved MPG comes from two things: Reduce road load and reduce engine frictional HP. The engines are pretty well sorted out for MPG so you'll spend a ton of money and not improve MPG a bit.

Some aspects of "hypermiling" (high-MPG driving) work well. Some don't and some are only for the certifiable (i.e. drafting within 10 feet of semis).


By their nature pickups generate a lot of variables. You have to figure out what works for you. That's what the stickies are about.
 

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Tires are 1.8" taller and 2.6" wider not a drastic difference.
My tires were 10mm wider and probably an inch taller. It was a major hit to my MPG, around 10%. It is a drastic difference. I couldn't escape the reality.
 

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I have talked to literally hundreds of guys about tires & wheels. I have yet to find one who got better MPG with bigger (either wider or bigger diameter) wheels and tires. AND getting too small hurts MPG as well.

Believe it or not the boys at the factory do have a clue. For Powerstrokes a 235-85x16 tire is tough to beat for MPG. Also absent real data (which tire companies treat as proprietary) on rolling resistance, you can safely assume that whatever came on it OEM has the lowest rolling resistance you can find.

In theory, smaller diameter, skinnier tires should get better MPG. Look at the super-high MPG clown cars. Teeny little tires and wheels and big MPG. But trucks are pinned by the gear ratios available. Smaller tires require outrageously (numerically) low gear ration or else the engine speed (at a given road speed) goes up and the engine frictional HP gets out of hand. for instance on my truck, to just hold what i have going to smaller (215-75x16) tires I'd have to find 2.73 gears for the drive axle. A 2.73:1 R&P set for a Sterling 10.25"? Ain't no such thing.

As mentioned in the sticky, you have to treat wheels & tires as four additional flywheels, which you have to accelerate every time you speed up. Accelerating a flywheel requires energy and (due to friction) you never recover all of that energy back.

Now if you can find some 9.25 inch wide by 31.7 inch OD tires that weigh less than OEM, you may be on to something.
 

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Dave,

Out of curiosity, since from what I have read you're one of the most into optimizing mileage around here, what would be the optimum RPM range for highway cruising? Right now on stock 265's, at 75MPH I'm running around 2200-2300 RPM. It would make sense that dropping it down to around 2000 where the torque peak occurs would help mileage to some degree, but what is the point where dropping RPM actually begins to hurt cruising mileage? I know doing this kind of thing would hurt in-town mileage, but I'm really curious.
 

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Running on OEM-size 235-85x16 Firebombs...

At 70 MPH, my truck is turning 1325 RPM.
At 60 MPH, my truck is turning 1100 RPM (or thereabouts)

The engine is most efficient at high load and low RPM - right on the ragged edge of lugging. Some people say the engine will begin smoking in that range, but I've never seen it. Might be because I wasn't looking for it.

Around town I can operate as low as 800 RPM.

I do not recommend this for trucks with automatic transmissions. They use the TC to circulate ATF into the cooler. Running high load at low RPM cooks automatic transmissions.

I get away with it because I have the German deuce-and-a half stick.
 

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Running on OEM-size 235-85x16 Firebombs...

At 70 MPH, my truck is turning 1325 RPM.
At 60 MPH, my truck is turning 1100 RPM (or thereabouts)

The engine is most efficient at high load and low RPM - right on the ragged edge of lugging. Some people say the engine will begin smoking in that range, but I've never seen it. Might be because I wasn't looking for it.

Around town I can operate as low as 800 RPM.

I do not recommend this for trucks with automatic transmissions. They use the TC to circulate ATF into the cooler. Running high load at low RPM cooks automatic transmissions.

I get away with it because I have the German deuce-and-a half stick.
Well that explains why my F-250 gets great in-town mileage....I try not to go over 1500 RPM in town just because it "feels right" when I shift around that point, and it has the stick.

Ok, so my Excursion has the 5r110 auto, so high load, low RPM is out. Should I be trying for a certain RPM range with that?
 

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Keep engine RPM under 2000 RPM at all hazard.

Under 1800 RPM would be better.

Industry engineers call this "downspeeding." It is the drive for 8, 9, and 10 speed automatics. These transmissions spend so much time in a TC-lock mode that they have auxiliary cooling pumps built in to circulate ATF to the cooler.
 

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That RPM range is about what I thought, but am glad to see you agree.

This question may be better suited to the transmission section so if need be I'll post over there, but if there is no coolant flow when the TC is locked up, how are they being cooled when running for long periods at highway speed? There isn't some secondary pump to keep a certain amount flowing?
 

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A taller tire will kill torque a little but not mpg I have 325/45/24's on my dually the tire comes out to a 35.5" rpms dropped at high way speed 2300 at 80mph I get about 16 mpg. The speedometer says 72 but my gps is on point. I would change tunes.
 

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Ok as I said lift and tires just put on. Clearly they aren't coming off. I am looking for reasonable suggestions

Tires are 1.8" taller and 2.6" wider not a drastic difference.

Mileage is with winter mix. NOT calculated with lift/tires yet. So far no change yet
Good Response
 
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