MPG is better with...

[84TD]

And if you throw a gear splitter in the mix how does that change things?

And if you throw a turbo in the mix how does that change things?

My main reason for asking this is I really want an auto but I dont want to give up a mpg. Based on my limited experience of only 4 idis, the auto loses, but I am wondering if a c6 with a spliter would be comparable to a ZF5

 

[Brianedwardss]

My 4x4 extra-cab ZF-5 IDI gets better mpg than my 2wd crew cab C6 IDI. The extra-cab gets 15-16 while I never top 14 wth the C6, even with 3.31 gears. I've verified and corrected both speedos too.

 

[dieselgiant]

compared to a c6 the manual would be better now the e40d with a lockup troque converter would be better than a c6 but not as good as a manual in my opinion

 

[Shadetreemechanic]

I am so far the lone vote for an auto. But having owned two identical IDIs, one with the zf and one with the e4od, I consistantly got better mileage with the auto.
The auto has a lower cruise rpm. To stay under 2K with the zf I need to stay below 70, with the e40d I needed to stay below 75.
Both had 3.55 gears.

 

[HammerDown]

With diesel fuel rising $$$...you can't get good enough mileage > anymore I hate turning the key

 

[bike-maker]

Seams like the mileage varies in these trucks quite a bit; hear everything from 12 to 20 mile per gallon. And there's lots of variables besides the tranny that contribute to fuel mileage. The true comparison would be someone that has done a tranny swap and kept accurate readings before and after.

 

[OnDaRoad]

Didn't see my option on the poll ...

Well .....

I noticed an increase of 3 m.p.g. when Bill got
out of my truck - but there was no poll option listed


Jim


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[Agnem]

I have an IDI and a PSD, both with automatics. I have 3 other trucks with manuals. Automatics blow. It's simple math when it comes to MPG. Fewer injections, mean less fuel being injected over a given amount of time. Any truck with an automatic takes more RPM's to get moving. Only the Auto's with a lockup clutch can compete, but then only at highway speeds, and they still **** away fuel trying to reach that speed. Any time the torque converter is not locked, there is a greater RPM being exerted by the engine to move the truck than what is needed for a manual. The aftermarket is going to have a field day with the new trucks, now that Ford in their infinate wisdom has decided to eliminate the most efficient transmission type during the worst economy in recent history. I can get 16,000 pounds moving without touching the acelerator on the Lady Moose. The 9000 pound Excursion can't get out of it's own way until you get close to 1800 RPM, and if you want it to get moving faster, better be prepared to hit 2500 RPM. That means in one second, the Lady Moose, assuming a fuel delivery rate being equal for both (not likely, since it takes more fuel to spin things which would only tip the numbers more in the manuals favor) of say 30cc/1000 uses .15cc of fuel where as the Moose Wagon would use 27cc of fuel. That's a HUGE difference. Now purists will insist that your probably putting more fuel into the manual trans to move the same weight, since the auto acts like a torque multiplier and that may be true, BUT I still say I can get the manual up to speed in less time and with less fuel than the auto, regardless of throttle setting. The only time the auto has an advantage is during shifts, but you only have to shift 4 times to get up to highway speed. That's not enough to make a difference. MPG with these trucks is ALL about injection events per minute. Because MOST of the time, your spending more fuel to spin the engine than what is needed to move the truck.

 

[84TD]

That makes alot of sense, very well put. Does your IDI have a turbo? I feel like I loose all my boost shifting gears and its takes a second to build it back up. Is that the same with your auto?

I didnt realize there are no a4od diesels. I wouldn't consider adding a computer to my truck so I would be comparing a C6 with a gearvendors VS a ZF5.

Ill probably end up going with the ZF but wanted some opinions. I just get tires of shifting with all the stop lights around here.

 

[franklin2]

The true comparison would be someone that has done a tranny swap and kept accurate readings before and after.

True comparison. Original tranny was a c6. Best mileage empty was 12mpg. Nothing changed but the tranny to a zf. Best mileage now is 15mpg. Just a tranny change gained 3mpg.

I have a N/A 7.3, completely stock with stock original injection pump, never turned up. 4 inch lift with 35-12.50-16.5 tires, 4.10 gears.

 

[Diesile]

I've got both an '86 and '94 F350/factory turboed standard cab 3:55 geared trucks. The '86 is obviously a transplant w/ZF5, and the '94 a E40D. Just as Mel says lots of rpm to get
going and waste heat that requires lots of cooling, something seldom if ever seen with the
bolt.

 

[Brianedwardss]

If we're talking best highway mpg, my 4x4 extra cab zf-5 got 18.1 on a trip once. The truck in my sig has only hit 15 mpg once, most trips I only clear 14. There's about a 600 rpm difference at cruising speed, so Mel's theory is obviously at work here.

 

[david85]

Its really hard to compare these trucks from one to the next since a bone stock IDI is about as common as hen's teeth around here

So far I have been able to squeeze 24 MPG out of my truck if I can limit myself to 55 MPH (completely empty, and no canopy). Gary has been able to see numbers that rival even mine out of his rig and we are both running E4ODs......Granted neither one of us is running a STOCK e4od.....

While I don't really want to disagree with what Mel is saying because it does make sense, I feel I should add that its a little hard to compare an IDI to a stock 6.0 since that powerstroke is a higher reving engine by design. No doubt a low stall converter could address this but ford for some reason decided against that. (I am assuming here that Mel is running a stock setup in the excursion)

 

[Black dawg]

I can lock my converter as soon as I am rolling with little to no difference in mileage.

 

[snicklas]

david,

Mel's Ex is a 7.3 PSD with a 4R100 Auto

Mine is the Ex with the 6.0 and a 5R110 Auto. I do agree with the revs, on a moderate excel, like trying to merge onto the interstate, not a WOT, but not creeping, my truck runs and shifts at a point that wound make most IDI'rs faint! , Well maybe except dyoung...... but on the throttle in this example, am tacking between 3000-and 3500 rpm, each shift holds to 3500, and the shift takes me down to 3000, and then does it a ll over again. But I also have the advantage, that when I am crusing on the interstate, with the OD and the 3.73 axles, I can run ~72mph@ 2100rpm, which is my most efficent place, I have gotten ~20mpg on the highway this way.

Also, the transmission is not a fair compairson between the two. I do not have to wind mine out to get it to move..... I have power transfer from the start, and an additional gear. So that helps also.