Fuel mileage 2-wheel drive owners

[Cummnzpowr]

OK. . i know this probably has been re-hashed a million times. BUT. . with a club cab dually,auto,with supposedly 3. 55's {rebuilt and replacing the old 4. 10's}. . i clocked it with 15 mpg running somewhat empty going from 65-70 mph. Can this be right? could it still possibly have 4. 10's?I notice it won't go above 75mph wide open. .

 

[Steve Graham]

Your mileage is about what I get with my 4:10s and 35s with my 5 speed.

Your suspicion are probably right about still having 4:10s, my calucations say that you should top out at 75mph or less.



Steve

 

[rdodd]

Cruising at a constant 65-70 empty on a trip and not using cruise control i can get 22-23 mpg in the summertime on a good day with no wind. My usual average miliage is 18-19 combined city & highway summertime. Winter miliage is usually several mpg less.

 

[Bob Beauchaine]

In Sept of this year I ran from Portland OR to Surrey BC and back with an average MPG of 23. 4 - I run 3. 54's. My summer agerage for all types of driving is 20 - 22 mpg and winter runs about 2 MPG lower.

Bob

 

[MRickard]

you can always jack up the rear and turn the wheel or driveshaft and count the revolutions of the other. Sometimes it is doubled/halved by the spiders rotoring though. Make sure tires are not low in pressure or real wide, and keep tailgate down for best milage. I get up to 24 on my 4x4, but with 245-70-19. 5 recapped terf tread tires (aprx 34" tall). Your milage could be right if your gearing is low and you drive fast, as mine will go to 17 at 75mph (tailgate up, empty), so take a little off for your lower gears. There is a fuel-curve that will gradually climb to an ideal speed, then usually drop off pretty quickly. I would see what you get going 50-55. As far as top speed for you, seems like you just need a little more fuel added for higher rpms... just like mine needs. Make sure you are running #2 diesel or higher, and if it is cold out plug up the radiator. You can dump in some engine oil in the tank and watch the MPG climb too (50/50 works good for steep grades!).

 

[BushWakr - RIP]

Depending on your location ... . keep in mind that we are now in the winter season and the fuel is now classed as "winter blend"... . my mileage actually changes by about 1 1/2 to 2 mpg faithfully. I treat it with Stanadyne PF and I get my mileage back as well as an improved idle quality and idle RPM.



bob... .

 

[JLEONARD]

With the 5 speed and 3. 54 ratio and empty truck witha FB cap I get 22 - 24 daily in a mix of 70% highway at 70 to 75 mph, 26 + on a trip.

Subtract 2 mpg for winter fuel.

keep tailgate down for best milage.

FWIW... . Article in TDR last year had study results that dispute this theory... they said with the tailgate up there is an air pocket that forms that actually pushes the truck. I think they said 2% gain with tailgate up.

I think both GM and Ford did the study... don't remember all the details just the bottom line.



Jay

 

[DKasper]

My '93 D350 auto w/3. 55's, 170k, gets consistently 17-19 mpg @65-70 mph. As noted, a little less in the winter, about 16.

I'd love to know what the difference is between mine and these guys getting 22 mpg -- that's a pretty sizable difference. Mine is bone stock and runs great. No smoke, so there shouldn't be any "wasted" fuel.

Any ideas guys??



Dave

 

[JCrank]

My '93 D350 is only getting about 10. 5-11 sometimes 8-9mpg. No load 55-65 mph. With A-518 and 3. 54 rear, 119,000 miles. I do have a fiberglass coated wood enclosure on the bed that is about 28 inches above the top of the cab, so I probably have a lot of wind drag. I wish I could get better mileage. I am probably taking the enclosure off and go to a utility body or tool boxes on the existing bed.

 

[JCrank]

My '93 D350 is only getting about 10. 5 -11 mpg @ 55-65 mph. Sometimes only 8-9 at the same speeds. I do have a fiberglass coated wooden enclosure on the bed, A-518 and 3. 54 posi rear. I've probably got lots of wind drag hurting me as the enclosure extends about 28 inches above the top of cab. I will probably do away with the enclosure and go to a utility body or tool boxes on the existing bed. Makes me want to cry eharing how much better other rigs are doing with mpg.

 

[Headshot zod]

170k miles 5-speed, the best I did was 23mpg and the best with the ac on was 21mpg. Time to get a carbon fiber propeller shaft and lightweight rims.

 

[Bluebird]

My average (combination) this week was 19. 89mpg. This has been my highest average ever. I have got 26mpg once, freeway only, on ramp to off ramp. I usually can get 23. 50-24 highway, and 16. 30mpg has been my lowest. At this time my lift-pump looks a little damp, and my injection pump is leaking a little. I hope she keeps going till I replace both, say prayers for the Bird...

Happy Holidays everybody, look out for the other guy. A full sized crownvic security cruiser just barely missed my front end in an intersection last week!

Cheers, Patrick.

 

[paccool]

Crank,



You have a problem somewhere! When I tow my 7000# travel trailer I get around 12-13 depending on terrain. If pulling long hills it can drop to around 10. The trailer has a hell of a lot more wind resistance than the shell you are describing. Empty I get 19-21, depends on how heavy my foot gets on takeoffs, etc.



I suspect you have some injectors that are not spraying the way they should and you could also have a timing problem with the pump. You could also have a converter or transmission problem. Do you have any gauges?



Greg, keep the speed down to around 65 and see what you get. As MRickard said, do the rear wheel spin thing and count the revs on the shaft. This is a good way to tell whats going on with the gear ratio. Topping out at 75 sounds like mine before I changed the ratio back to 3. 55 from 4. 10'S. Funny thing was it didn't seem to make any difference in fuel mileage. Got the same as before.

 

[Cummnzpowr]

mileage

Stan. . thanks for the advise. . however i am thinking now my speedometer is reading SLOWER than actual speed traveling. . for one,the odometer is broken at the moment thus maybe causing the speedo to run a little funny. Maybe if i go 60-65 on the gauge i'll get 18-19. . instead of running on the floorboard at 72 . .

 

[AndrewKing]

I get 20 mpg running 62 mph empty... . I hope to get better w/ a 4" exhaust and pump timing change.

 

[JLEONARD]

I hope to get better w/ a 4" exhaust and pump timing chang

well, you'll at least get to speed faster and have a bigger

Jay

 

[JCrank]

Nope, I don't have any gauges as yet. Plan to get some when I get some extra $$$. I'm running empty most of the time, except for maybe a chainsaw and small toolbox. I'll check into the pump timing, injectors and transmission items soon. I do know that when we hooked the truck up to the computer diagnostic tool, there were no fault codes, except 12 and 55. The only other thing I noticed was that the computer said there was "no tach signal". I had a PCM problem and had to splice an external voltage regulator in. I had problems with the transmission wandering from OD to 3rd and back and forth. Transmission band adjustment seemed to have solved this problem as well as cleaning wiring connectors.

 

[Mel Fuelling]

In my '93 5 speed/3. 54 dually that weighs 9k, I usually get 19-20mpg @ 65mph on cruise on #2 summer fuel, 17-19mpg on winter blend; have gotten 23mpg twice @ 62mph on cruise, and twice got 25mpg @ 55mph on cruise. (I guess its been 2 years since I got the 23 & 25mpg. It was a little dangerous trying to drive that slow even on secondary roads in Iowa. ) This truck seems to get better mpg @ 75+ mph after I advanced the injector pump timing than it did before.



In my new '93 automatic/3. 54 dually that weighs 5,740# empty, I usually get 17-18 on cruise @ 65 on #2 summer fuel, and I expect to get 15-16mpg on winter fuel. (It probably would benefit from gauges and minor enhancements that the 5 spd has, but I want to service and adjust the automatic to give it a chance of survival first. )

 

[JCrank]

I do know that my truck had been parked for almost two years as the previous owner could not solve the problem of the battery not charging. He had changed the PCM, crank position sensor and alternator, but didn't solve the problem that I did when I put the external regulator on.

 

[dpuckett]

15 is low, even for an auto. If it has 4. 10s, it should get within 1-2mpg of 3. 54s. If you're topping out at 75, you have either 4. 10s or bad pump troubles. Mom's will do 70 in 3rd, but only about 90 in OD- too loose of a TC, I think. Mathematically, she should do over 100. With her weakening auto, 3. 54s, and in town driving, she averages 17-18 year round. I am down to about 18 in town (8mi to work, never see 50 unless I am in a big hurry, then it's 65), 19 hwy with my 4. 10s. I have seen 23 at 6-7000ft (less wind drag, better fuel), with no appreciable wind. Best in MO is 21.



JCrank, you definitely have issues somewhere. Fuel filter, timing, and valves are good places to start. I got 13-14 with a GCVW of 23K going 60-65 with a load of hay on a 93 D350.



Daniel