Mileage question again

[SF Jakey]

Well, here is my first post, or question I guess. I can not get over 15 mpg to save my life in this truck and the dealer says they can't do any thing about it. I've never owned a diesel before and I completely love this truck, but can't help but feel that something is not right. The only change I've made to the truck is 285/75/16 tires. I recently towed my 7000lb fishing boat down hwy 1 from SF to Santa Cruz, under 60 mph all the way, and while it performed awesome, mileage was 8.8 mpg for the trip. Shouldn't this truck be doing much better than this? If not, what modifications would you make to increase fuel economy, since I think it has all the power I'd ever need. Thanks for all the input, you guys really know your stuff.

[NutNbutGMC]

I used the free search tool. Found these on mileage.

1) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002103.html

2) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002078.html

3) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002027.html

4) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002050.html

5) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002003.html

6) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/001988.html

7) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/001818.html

8) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002112.html

9) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002128.html

10) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002166.html

11) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002170.html

12) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002113.html

13) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002194.html

14) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002199.html

15) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002213.html

16) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002280.html

17) http://www.62-65-dieselpage.com/ubb/Forum3/HTML/002291.html

I gave up on counting the mileage threads. Hope this helps.

[RWHP]

SF Jakey,

I can feel your pain, like you my milage is far from what SOME people claim they achieve. Driving around town I get anywhere from 14.5 to 16.5, and it mainly depends on where I buy the diesel from.
Dont feel bad just some people have an extreemly light foot and others just like to exagerate by posting numbers that they have managed to achieve only 1 time.
I too have gotten an amazing millage reading 1 time but then I realized that the next tank was horible and the reason was that I just way under filled on the previous fill up.
That being said, there are pointers I can give you on towing with this truck. This can greatly increase your millage, easily to 11-12 mpg. As an example my crew guy was towing with my truck and trailer for the first time last trip. His performance was this:
1-9.6mpg
2-9.2mpg
3-8.5mpg
Then I started toutering him.
his next three were this.
4-11.4
5-10.6(He downshifted 2 times)
6-11.85
Follow the instruction below and you will be good to go.
1) You must tow at least 75-80mph. May sound a bit fast but this is the only way to keep the truck from downshifting on every hill it encounters.

2) If you do run accross a steep hill that will require downshifting, turn off cruise and press the pedal about half way to make sure the truck does not downshift. You can become accostumed to the right amount of presure by playing with it and listening to the turbo whine.

3) Never alow your truck to downshift unless you are actualy going slow enough for 4th gear to be reving less than 2500. If it does even 1 time the millage will suffer horibly on that tank.

4) Fill diesel only at stations which sell alot of it, otherwise you are going to pay for it with millage.

5) Make sure you follow rule 1, since it is by far the most important. No way around it.

*Pray for someone to make a product which locks in 5th gear.*

[srubrn]

Sorry about your mileage. I have a 02 2500HD D/6sp. Every time I fill up after driving around town I get 17 to 18mpg. Mostly it is 17.5. I have a heavy foot too. Only mod to date is a Flo-Pro muffler. It didn't change it much mabe 3/4 to 1 mpg. I got 19mpg on the hwy. with cruise on 70. Running 80 to 90 I still got 17.5mpg. I have made only one trip towing. I was towing a 32ft 5ver and was on a two lane road cruise on 70 and passing people, very hilly too. I got 10.8. One trick to make sure your readings are accurate, fill the fuel tank all the way up to where you can see the fuel in the neck. Otherwise you will get some discrepency.

[woundedbear]

I am sure that with your milage calculations you accounted for your odometer being 4% on the light side (i.e. 104 actual miles for every 100 miles on the odometer for a 285/75 tire). Hence, if you did obtain a 15MPG average from calculations done from your odometer, your actual MPG would be ~15.6MPG.

I have a crew cab, short bed, Allison auto, 4WD, and since birth (now @ 6100 miles), has averaged 16.6MPG. I have kept very detailed records to validate the numbers, as well. I live in Wisconsin, so it does not get as cold as it does up where your at, but ever since it has started to warm up, my 5 tank moving MPG average has increased and I only expect it to get better. I'm sure yours will improve when the warmer months arrive.

One other note...I've noticed that when I hit the freeway before the Allison allows the fifth gear shift (~185 degrees Fahrenheit) many times in one tank, my mileage will greatly decrease.

[MudNurI]

I can't figure out how some people CANT get 15 mpg with your truck..I'm not trying to brag, but we have never gotten less than 17. that includes city driving. on our trip the past 2 weeks we averaged 21.5 and that was with some pretty big hills etc.

as for the downshifting, I'm not sure why your trucks are doing that either. once I hit the highway, my truck doesnt come out of 5th until I get off the exit. I don't think I'm driving any different than anyone else. this is using cruise- set at 74 usually, and without using cruise.

as for the 75-80 mpg driving when towing- that's just plain INSANE! could you imagine the $$ the ticket in Virginia- where the speed limit is 60. holy big $$.. I guess if your worried about saving money at the pump, you really shouldn't drive that much over the speed limit, because all the money you save, is going to head on over the local cop shop..or heaven for bid your trailer started to sway and you lost control...you pay a lot more to me, if its me coming the other way when you lose it...

Since there is so much discussion on this board regarding MPG, there has to be more to it than just driving styles, climate, and road conditions. we live in VT, where its been pretty darn cold, and we have big mountains to go over and our mileage wasn't that much better in Florida, where its flat, and hot..???? and I drove the same way.

wierd huh?

Brandy

[GMC-2002-Dmax]

Got 1980 miles on my truck, 6 weeks old

17.90 highest MPG - so far
16.75 Lowest MPG - last tank ( don't think I had it topped off! )

Combo around town 35-50 mph and highway 75-85 mph avg.

I drive it like a truck. I don't baby it and use MOBIL DIESEL from the same station everytime.

D/A CC-SB 4x4

GMC :rolleyes:

[Lone Eagle]

RWHP, You forgot to tell him to increase tire pressure. This made a big difference with my last gasser. I haven't towed with my DMAX yet and it is killing me. Only two more weeks away. Later! Lone Eagle ;)

[bhinrichs]

How many miles have you got on your truck?

I have an 02 Indigo Blue 4x4 CC Long Box.

I never got over 14 for the first 3000 miles.

This was during December, January and February in Colorado and Nebraska.

I started adding a little FPPF Total Power to the fuel and switched to Delvac 1 at 5000 miles.

I'm now at 11000 miles. Since 5000 miles I haven't gotten less than 16 miles and I am averaging 17.7.

I drive 80 mph on cruise on mostly flat interstate unloaded most of the time. There is only a little city driving in those averages and only a little light towing (16 foot flat-bed on 60 mph 2 lane roads).

Bert

[Allison Jettester]

02 GMC 2500HD EC LB DMAX/Allison 285/75R/16

I picked my truck up new in Michigan in Feb (OAT 49F) and drove to Maryland. Filled with Shell Premium when I left and got about 19 mpg in 537 miles (I say about because I don't think I got the tank completely full). Filled with Sunoco and got 20.1 the last 320 miles. Since then mileage varied as I only live 2 miles from work and most trips have been less than 8 miles. The engine never gets to operating temp with these short trips. Mileage started dropping steadily when I started using Mobil (because the station is next door) from 17 to 15 and trips started to get shorter. The last in town only tank, I got 14.9 mpg with Mobil. I drove 460 miles mostly highway on Friday with mobile and got 17.1. I filled with Exxon on Sun and drove 340 miles and got 21.1 with speeds 65 - 80, but mostly 75.

As with gasoline, there seems to be a tremendous difference in the brands. I am now going to stick to Sunoco, Exxon and Shell.

Also, I did several measured mile checks with the 285's, one for 30 miles and my speedo is exactly 10% off. I had these tires on my 95 GMC and they also measured exactly 10% off (reading 60 and using stopwatch actual speed was 66). I know the math calculating the tire diameter does not support this, but maybe the tire dynamic diameter is larger than static.

When you guys/gals (gotta be politicly correct)post mileage here, it would be helpful info to include truck brand/configuration and fuel brand used.

Joe

[ 04-02-2002: Message edited by: Allison Jettester ]</p>

[MudNurI]

here's my specs

2001 2500 HD crew cab D/A stock sliperstone tires, no mods, the road trip we took we used flying J diesel- i have no idea what "brand" they use, but all but 1 tank was from their truck stops, the 1 odd was Hess.

when were home we use diesel from a big tank in our shop yard, from some 18 wheeler that comes and fills it up... smile.gif

no mods to the truck either.

Brandy

[SF Jakey]

Thanks for the replys everyone. I know I'm beating a dead horse here, but it drives me nuts not knowing what is going on. I have been multiplying my mileage by 1.078 (difference between stock 245's and new 285's) to get my figures and I also try to buy fuel only from places that sell ALOT of diesel, which usually means a 10-20 mile drive to get it. I use chevron delo 15-40 oil, GM filters, and don't stick my foot in it because I really want to see that 18 or 19 mpg tank. Truck has 8200 miles on it so maybe its just not loosened up yet. Oh well, if this is the only problem I have, I'll be OK, it just seems to me that poor fuel consumption is an indicator of something more substantial going on. Thanks again for the info guys, and hopefully I can help someone else out also.

[NJDMAX]

I've filled up three times:
16.4 lots of highway 65-75 mph
15.2 around town 40 mph
15.6 around town with some highway

the truck is a GMC K3500 crew cab D/A with m/s tires from the factory with 1680 miles now.

[Tim B]

I have a new one - 4x4, Ext Cab, Short Bed, Allison trans. Only filled up once and it came out to 17.8 MPG. About 85% town driving. What amazes me the most is that this truck replaced a 4x4 Blazer - which always averaged just about 17-18 MPG running around town. Let's see, the truck weighs about 50% more and makes 50% more HP. I think I like this trade !

Tim B.

[Tim B]

SF Jakey - What's the air pressure in your tires ? This could make a big difference. According to the sticker on my door, for stock tires, the fronts should have 55 and the rears 80 PSI. But I don't run 80 when not towing.
* I saw that you don't run the stockers but the tires should indicate max inflation on the sidewall. This will be a good starting point.

Tim B.

[HD=HossDiesel]

I get about 15 around town no matter what I do. However I went to Daytona in February and In the warmer weather the mileage definitely improved. My Father drove the truck down and back and reported milage as high as 20.5 mpg. He swears the Faster you go the better it gets they spent as long as 20 minutes right at the limiter when they achieved the highest mpg. It sounds nuts but hey thats why I flew!

[hardwood]

RWHP,
I agree that we need a product that locks 5th gear. I posted a thread a while back about this phenomenon - the allison downshifts very easily when towing up a steep hill. When I pull my 12,000 # dump trailer, she downshifts all the time, especially in cruise. The cruise trick helps somewhat.

SF Jakey,
With driving style aside - the fuel supply needs to come from a trusted source, and try to get fuel from the same source consistently. If you are using Diesel #1, your fuel economy may suffer considerably. Also, depending on the year of your truck, there have been issues with the MAF sensor getting dirty and the aluminum sticker sucking into the air intake - something that may pertain to your situation. Just some ideas...

[MudNurI]

What is diesel #1???

the inside of my doors says front tires at 55 rear at 50 not 80???


Brandy

[trailguide2u]

My mpg has dropped since new from 20-21 to 14.5-15.5. On long warm ups the motor drinks the fuel. I have not used the winter front due to the weird winter temps (45 one day 10 the next). The truck struggles to 185-190 degrees at 20-30 degree temps even at highway speeds. I am betting that with warmer temps and no warm up with straight #2 diesel that mpg will go up. I would believe that the computer richens the fuel supply until full operating temp is achieved. Any idling (stoplights) it cools down and back to a richen mode again. Just my opinion.

I will be adding Kenndy's exhaust and a Amsoil air filter soon. This should help.

[ 04-03-2002: Message edited by: trailguide2u ]</p>

[Tim B]

#2 diesel fuel is what you find in the summer. But #2 starts to gell when the temp drops to about 20 degrees. #1 is thinner so that it will flow and not gell up in winter temps. But a side effect is that you get worse mileage (and power I think) with #1. Also, #1 does not lubricate the pump as well. Just to muddy things a bit more - - - some stations cut their #2 with chemicals in the winter and some blend #1 and #2 in various proportions depending on how cold it is. You just haven't lived until you've had a diesel gell up on you while you're cruising down the interstate in below zero temps. I learned that in the winter up north it was real important to know what 'the mix' was at the local fuel station.

Tim B.

[MACGMC]

Just recently joined and this is my first post. Thanks for all the great info. which led me to purchase my DMAX 02/02. Been reading all the posting on mileage as I've been a little disapointed on my mileage. Have a 02 CC/SB SLT, 4x4, 265/75 tires & K&N filter, approx. 4500 miles. Best mileage unloaded is 16.5, but I'm always the first away from the light. Towing 3 sleds in enclosed/5300lbs going up 10mpg/ downhill 12. Just towed my New Vision 5th wheel/14000lbs to Topeka,KS and back averaged between 7&8. My mileage is consistant with most and way off of others. But I'll wait and see if its gets better, at least I had the info. from this site to compare with thanks again for the info.

[Vette Racer]

My CC dually gets about 16.5 combination driving. No heavy duty towing yet. About 14 with a 5000lb load at 70mph. Will let you know when I put it to the real test when I put the 17,000 load on it in July.

[MACGMC]

During a recent trip with 5th wheel I discovered that the faster I went the better mileage I got. Doesn't make sense, but my worst mileage was with my wife driving 65 to 70 ( 6.8 mpg). Going 75 to 79 I got 8. But the weather was bad looking forward to warmer weather towing for the real test. Its still the best truck out there.

[RWHP]

MACGMC,

The reason you got better millage is simple, the faster you go the less the truck downshifts. If you got your speed to 85 it would be better yet.

My average towing with me driving 80-85 is 11-12 mpg, and this is going up hills. There is no flat ground on the west side of the US. When you start towing to the east it seems to be all uphill.

PS. Anyone notice that no matter what the road always seems to be uphill? What is with that!!! :confused:

[Wally]

Jakey,
You never do say whether you are correcting for the Odometer error. On my truck the 285s make exactly a 7% error, checked over a hundred miles with Interstate mile markers. This can make a big difference. Example: 365 miles(indicated) 23 gallons 15.87mpg. Corrected=390.5/23gal=16.98mpg

[BobNelson]

Wish I had a good answer for you... Gotta be something wrong with your set up... I have been keeping very accurate records on fuel, price, milage since day one. 15.1 at nearly 20k miles. Worst milage was when fully loaded, in the back country of Idaho, on winter fuel. 12.1...

Again, gotta be something wrong with your set up... I think my tractor beats the 9 mpg mark... ;)

[team trim]

what rpm are you running at 60 mph? I had a 2001 2500hd 4x4 extended cab short box that ran 400-500 rpm higher than my 2002 2500hd 4x4 crew cab short box. this makes a large difference. never did get to the bottom of this with service manager as sales came through for me and i traded it in. 2001 low of 9.5 mpg high of 17 mpg (1 tank). 2002 low of 13 mpg high of 20.5 mpg and this truck only has 6000 miles on it.

[maxtotow]

Since, the topic is up again.
We just got back from a trip, Louisiana to West Virginia.
Total miles 2693 using 139.03 gallons
2693/139.03 is about 19.37 mpg
Calculating over this interval eliminates the problem of inconsistent topping off, it is hard to top it off the same every time. This average includes interstate at 70+, in town driving with some traffic jams, mountain driving, sightseeing and so on.
The highest single tank calculated was a short tank fill, 23 mpg with Mobil fuel; one 14 gallon tank fill, 22 mpg with Williams; and lowest was a 10 gallon fill, 16.4 mpg with Sheetz diesel and driving locally in the West Va mountains. We sometimes used Rotella DFA in the fuel, but not every tank. The milage seems to vary more with this truck, but i think that is due to the topping off problem. We are very happy with a vehicle that has 4 doors, lots of room, lots of power, lots of comfort, and weighs 6000 lbs.
We noticed when we got home last night that the tick was gone. for good? 4500 miles total on truck, 3200 miles on last oil change.

[56Nomad]

Hello SF Jakey From: Novato,Ca

All California 2002 DMax's are different from the
rest of the 49 States. The CA 2002 models have the
following:
A Catalytic Converter
Exhaust Gas Recirculation (EGR)
Revised Cylinder Heads

I've wondered if this might be the reason for a
some reduction in mileage in CA trucks. I know
that all the new Dodges and Fords diesels sold
in CA also have catalytic converters.

[SF Jakey]

First off, thanks for everyone's responses. Sorry I haven't been able to reply, but the computer was on the fritz. I'm running 60lbs in my tires and yes, I am compensating for the larger tires when I calculate my mileage. I'm thinking very seriously about changing the exhaust and air filter to improve mileage. Does anyone think this would make a noticable difference? Secondly, since this is my first diesel, I'm not sure what are normal sounds. When I drive 70 mph on freeway, the truck turns about 2100 rpms, but I can hear the turbo whine very distinctly at this speed, is this normal with no load on the motor? Perhaps this is causing my poor mileage, just a thought, let me know what you think.

[zrone]

I just returned from a trip after picking up my new Excel fifth wheel. I picked it up in Wisconsin, drove to Kansas then drove back to Long Island N.Y. Its weight is about 14,00lbs. Worst milage was 8.5 in the rolling hills of Iowa with a 30mph headwind. Best milage was 11 even in Indiana with the cruise set a 65mph. On the way to Wisconsin with no trailer and averaging 70 mph milage was 16.9. I tried setting the cruise at 30mph an was able to lug the engine up hills without downshifting and I also tried setting the cruise and letting the engine do its own thing. The milage was very consistant either way. In fact my best milage was with the cruise set at 65mph.

[fasterthanyou]

I have a 2001 cc s/b d-max that I use to tow my Extreme Rock Crawler in a 30 box trailer (triple axle). She weights 12,000# loaded and I tow about 80% of the time with a fellow competitor in front of me towing equall weight. He drives a '99 ford with a diesel and no mods. Notice I said he tows in front of me, this is because he must break the head wind to allow me to go 85 to 90 mph. Otherwise, I can't keep up. My carpet at 35,000 miles has a hole in it under the pedel from flat footing it everywhere. My calf has veins in it that were not there when I had my last truck. I get 5.5mpg towing and 10 mpg not towing. This is a joke. The ford pulls away and gets 15 mpg. I have a 2003 Dodge on order already. I'll ditch the order IF I can fix this POS, otherwise the resale isn't that bad.

[SoCalDMAX]

fasterthanyou,

Based on what you said about your truck, sounds like you picked the wrong forum name. I'm a little skeptical about your competitor's PSD getting 15mpg towing at 90mph. My neighbor's PSD gets only 14mpg unloaded, 10-11mpg towing a jeep on a flatbed and camper. I also don't understand how he could be ahead of you, assuming equal trailer weight and wind drag. PSDs dyno at about 175 to 190hp and the Dmax does 241-243hp, so you should be at least 50 or 60hp up on him. If you're both running auto trannies, you've got one more gear as well.

Why do you call it a POS? Do you feel it's an inferior product or is it defective?

If you'd like some info/help trying to figure out if there's something wrong with your truck, you've come to the right place.

If you just stopped by to let us know you're buying a Dodge, Congratulations!

Steve

[pinehill]

In FasterThanYou, we have either,

1. A guy with a very sick DMax (I assume, since he didn't say), who is so terribly concerned about it that he fails to request help or provide any data other than mileage

OR

2. A provocateur from the F or D darkside.

I'm going with number 2.

[RWHP]

FasterThanYou,

Interesting story there with your friends POS, oops I mean PSD(Sorry). I frequently tow with several people accross the country and all of the have Fords. Here are some of our observations.

1. My load is about 3k-4k higher than theirs, since I am the only one towing a 2 car hauler vs a single. This will come into play with millage and towing performance.

2. My gas millage is about 3mpg better than theirs, and mind you this is with a heavier load. And we are all traveling about the same speed(when they can keep up).

3. Up hill I can pull away from them at ease, we have tried several times just for curiosity sake.

Needless to say when they are ready to trade in their trucks, they all say that mine is the one they would buy.

PS. Another great feature of Fords is how the rear end locks up on you, my friend had it happen to him 2 times. Is this a good thing for a 2001 truck? Dealer fixed it both times, but it did cost him a whole race event since the truck broke down on the road.

[fasterthanyou]

I appreciate all of your input very much. Of course I would like to find a soulution to this problem. It is a hell of alot easier to fix this problem, if that is what it is, than to go get another truck. Things I can tell you about performance, or lack thereof: It is quicker at 3/4 throttle than full throttle sometimes, how can this be? It has horrible flat spots at 50 mph and 74 mph. You can't use cruise when towing or it shifts until the trany temp max's. After maxing the tranny fluid 4-5 times I changed the fluid and driving habbits. I have had the windshield whistle on the way home from the dealer, new, and brought it in 3 times to get fixed. They couldn't figure it out and I got mad and punched while talking to the service advisor adn shattered it. Some mobile windshield company I paid for replaced it, and fixed the whistle, on the first try! The drive-shaft vibrated and I complained for 2 months. Then a bulleting came up at the dealer, and the replaced it with a one piece, it still vibrates, spring wraps, but it is bearable. The tranny sucks. It feels like I get rear ended everytime I stop. When I try to pararrel park and tap the gas once, it goes, then stops, then surges once hard. It will be towing a grade in 4th gear, then downshift to 3rd, then as the grade flattens, it upshifts to 4th after the power goes away and then boob screach! the tranny kicks into 4th so hard the rear axle smacks the bump stops and the tires light with 2500#'s of tounge weight. Love it! Regarding the comments about the Ford, it pulls away from me everywhere, and has since this truck was brand new. I have driven a 2002 d-max from the dealer and it drives the same as mine, except 1st gear is not as fast as mine and the tranny shifts a little firmer. As far as specs go, I have a crew cab, s/b 4x4. I have a tag-along trailer 12000# loaded. Airlift bags and compressor. I have had it serviced regularly by competent people. I have a K & N air filter I clean correctly and don't over-oil. The dealer has re-flashed my computer for some tranny fix that did nothing. They also ordered a new air filter box and mass air flow sensor, last time it was in for and emergency, raining and the windows wouldn't roll up and the headlights were stuck on high beam. I think the truck was great, or I wouldn't have bought it, but I need to spend time on my race effort, not my tow vehical. That is why I feel it is a POS and have the new Mopar on the way.
Jason

[pullinpower]

yea OK :D :rolleyes: Have they changed out your fuel filter,that flatspot sounds like a lack of fuel.As far as a 99 psd "even if he had a chip" out pulling your truck even when it was new doesn't sound right.I would go check the airbox and the fuel filter to make sure your mechanic is doing his job.

[ 04-10-2002: Message edited by: pullinpower ]</p>

[Tractorhauler]

Jakey,

I just returned from a long trip 3700 miles towing anywhere from 5000 to 16000 lbs. Average on the entire trip was 9.5. With wind and hills it would mostly be in the 8.8 range with 16000 lbs. I have an amsoil filter with a Banks SS 4" exhaust.
I was definately pleased with these numbers.

[MNBowTie]

Pinehill,

I'm with you on this one. Just call him a wambulance and move on to the more sincere issues that need to be discussed.

[pinehill]

MNBowTie,

I used to live in Brooklyn Park -- on Tessman Drive, just off 152 (MANY years ago). Viva Jesseland! :D

[konacat]

Picked up my new 2002 2500HD Dmax crew cab long bed on 3-29=02. Now have 1450 milse on it. It was built 3-10-02 and was purchased in California. The drive shaft is two piece if anyone wants to know. The first 500 miles were spent driving up and down the rpm range and not going over 65mph. Most of the rest was spent on the cruise control between 58-74mph. Most miles in the rolling hills of the gold country with some city and mountains included. I am also using Power Service diesel additive purchased at Wallmart. Can't wait to tow my 10,200 lb 5th wheel

First tank of diesel was 17.5 mpg.
Second tank was a tick over 19mpg.
Third tank was 18.52mph.