Dmax/6 Speed Mileage

Crafty1 · January 30, 2001

On my 3rd tank of fuel I got 17.8 mpg with my Dmax/6speed 2500 4x4. It was almost all city driving. I travelled 570 km's on that tank and went over 50 kms after the low fuel light came on. It took 90 litres to fill the tank so that means I only had about 8 litres (2 imp gal.) left in the tank. I'm planning a trip next weekend that will be over 600 kms round trip so I will find out then how it does on the highway.

I also plan to get the truck weighed this week to see what the weight difference is between the 6 speed and the allison. If you are all interested, I will keep posting updates here as to mileage etc since there are very few manual trucks out there.

Kansas Kid · January 30, 2001

Don't know about the others, but I am interested in hearing your updates. You are our only source of DMax/ZF information, so keep it coming.

Crafty1 · January 30, 2001

Consider it done then. I will post weekly or bi-weekly mileage updates and anything else that I think would be of interest.

If anyone has questions at any time, please feel free to post them or email me and I will try to gat the answers for you.

cjacques · January 30, 2001

I say keep posting. Crafty, your fuel mileage is looking pretty good so far. You may be one of the few people to get an HD with the 6-spd. BTW, does anybody have any new word about the potential for anymore ZF equipped trucks being built? Thanks for the info.

Kansas Kid · February 2, 2001

Hey Crafty,

could you measure the ground clearance of your truck at the transmission crossmember for me? Just looking to see if there is any difference between a Dmax/Allison and a Dmax/ZF in ground clearance.

One more question for ya. Was the transmission fairly stiff to shift when you first got the truck, and if so is it loosening up any? I know this seems to be common with HD transmissions.

Thanks in advance.

Crafty1 · February 2, 2001

Hi Kansas Kid,

I'll crawl under there tomorrow when I can see to read the tape. By the time I get home tonight it will be dark and it is snowing AGAIN so things will be a mess underneath. I'm curious what the clearance actually is too.

As for how stiff the tranny was, that is a yes. I found it very stiff compared to the 4 spd manual that I had with the 6.2. The truck has over 1800 km (1100 mile) on it now and things are shifting alot easier. I have to keep reminding myself to use 1st gear every now and then so that it gets broken in as well. You only get about 1 or 2 car lengths in first before you hit 2500 rpm so I don't use it much. After a few more miles I think the transmission will work really well. You can tell it is heavilly syncronized but once I figured out the shift points on the tach (both up and down) it just drops in very easily.

I took the truck to a weigh scale the other night to see how much difference the auto vs manual makes with the weight. My truck weighed in at 6360 lbs with me in it and over 3/4 full of fuel. That means it weighs about 6180 lbs after subtracting my weight. I have seen other posts that say the Dmax/Allison has been weighing around 6600 lbs so the tranny must add about 300 to 400 lbs.

At the weight for my truck that leaves me with 3000 lbs of carrying capacity. Not too bad at all.

Zane · February 2, 2001

Wow, thats great milege. I'm kinda depressed hearing it becuase i'm only getting 12mpg on my Zr2!!!

Kansas Kid · February 3, 2001

Don't worry about finding out the clearance if it is too much of a mess. I hate laying around in the snow to work on my truck, so I imagine you aren't too fond of it either.

I do like the weight you posted for your truck. 3000lbs of carrying capacity is great.

btw, I did finally see a production ZF truck last week. It was behind a 8.1 though. Talked to pontiac on PUTC chat on Monday and he said they still aren't putting any ZF's in the trucks. Haven't been for some time, and aren't going to for awhile. He hadn't heard any rumors as too why. You are going to have a rare combination there.

(Edited by Kansas Kid at 9:57 pm on Feb. 2, 2001)

Crafty1 · February 5, 2001

I got the clearance measurements from under the truck this afternoon. My truck is equipped with skid plates so I measured from them as they are the lowest points.

At the front it is 8.5 inches from the ground to the front edge of the skid plate. At the transmission cross member there is 9.5 inches clearance from the ground to the skid plate and 10.1 inches from the ground to the cross member itself. At the back there is 8.0 inches from the ground to the bottom of the rear end housing.

It's the first time I've been under the truck and I can't believe the size and strength of things under there. The transmission is twice the size of my previous truck and the muffler is half the size of a 45 gallon drum. (at least it seems like it) I looked for grease points etc but I only found a few of them. It was getting cold and it was snowing again.

I had thr truck up to 85 mph today and there is not one bit of vibration at all. Real smooth.

If you need any other info, be sure to let me know. I will have more mileage figures etc later this week.

Kansas Kid · February 10, 2001

Crafty,

how do you convert Imperial MPG to standard MPG? Just wondering if you had already done that to your mileage figures.

I would have a hard time using 1st gear on that transmission. On my cousins PSD, it isn't even really necessary until you hook about 10,000 lbs on the truck. And then it just goes when you let out on the clutch. I would imagine the Duramax is the same way.

Crafty1 · February 21, 2001

The mileage figures I've been posting have all been using imperial gallons. The conversion diference is as follows,

If you have 90 litres of fuel, that converts to 19.8 imperial gallons (90 x .22= 19.8) or 90 litres to US gallons coverts to 23.76 US gallons (90 x .264 = 23.76) This means that the 570 kms (354 miles) that I went on my last tank of fuel is equal to 17.9 mpg (Imp Gal.) and 15.2 (US Gal). To convert kilometers to miles you multiply by .6214 and then you use either the .22 to convert litres to Imp gals. or .264 to convert to US gals. It is on big mess having to use litres and kilometers up here. I hope this helps everyone figure out the difference.

I never made that long highway trip I was supposed to go on a week ago. The weather up here has been too unpredictable so I will try again early in March.

I was in conversation with a neighbour this week who has a Ford with a 6 speed. His truck has 150,000 kms and he has had to repair his transmission once already. He regularly hauls a ten horse trailer all over parts of Ontario and the northern states. After I get a hitch installed in mine, I offered to haul a load for him this summer to see how the truck compares to his. It should be very interesting to see what he thinks.

After 2500 Kms everything is just purring along!!!! I love this truck.

Crafty1 · February 27, 2001

I just filled the truck again (4th tankfull) and the mileage this time around was 18.3 mpg (Imp. gal.) I think things are finally starting to loosen up a little more.

I showed the truck to a friend with an older Dodge with the Cummins engine. He could not beleive how quiet mine was compared to his. We ended up side by side at a light and I could hear his over mine with the windows up.

On the weekend I installed a full tailgate and front box protector along with a rubber mat for the floor. The two protectors are checker plate aluminum from DEE ZEE. I had them on the last truck and definitely wanted them on this one. I also had the truck rust proofed with "Krown" on Saturday as well. Anything I can do to slow down the rust process is worth it in my books.

I will post some new pics of my latest additions soon.

BROKER · March 3, 2001

Milage, well my new truck has 6200mi on it and it's dooing about 12m/gl. I have hauled a new trailer back from out west but it was empty.It weighs 5400lbs empty and is dragging three axels.It has gone for it's first load in Halifax N.S. right now ,we will see how it will do with 3 windstars on the trailer and what kind of milage it will return.

I'm surprised at the milage CRAFT1 is managing.

Crafty1 · March 6, 2001

I finally got my long awaited road trip in on the weekend. I am even more impressed with this truck now. I travelled 415 miles and over all I got 21.8 mpg (imp.) or 18.2 mpg(US) for the whole trip. On the way there I never had to shift out of 6th for three hours and I had the cruise set at about 120 kph (75-80 mph) for over half the time. The trip home was a little slower but I still was able to use the cruise for some of it.

Once the truck is fully broken in I expect the mileage to get better yet.