Chevy Duramax actual mileage results

[DKAir]

As for service intervals, costs, etc. I've been very impressed thus far but we're only at ~28,000 miles, purchased at 18,000. The way we use the truck (lots of highway towing with very few small trips or city driving), the oil life, at least according to the DIC, shows good much longer than I would have thought. To the point where it has shown ~30% when we've decided to get it changed, which has only been twice. I've been taking it to the dealership where we bought it (Chevrolet Dealer Minneapolis, MN | New & Used Auto Dealer | Miller Chevrolet Rogers, MN, Minnesota) as we had some free service coupons. We'll probably continue to bring it back there when we can (not traveling) as their prices are great and they always have free food.

We've also had the fuel filter changed with the oil changes. The wisdom of the internet says this is cheap insurance for expensive injectors, but I am not sure it is necessary as the DIC still shows lots of life. What are people's thoughts on this?

-DK

[tomp1937]

Have a '05 Siiverado Duramax CC HD 4x4 with 120M miles on it, 80% towing 28' A/S. Just replaced brakes, still on second set of tires (Firestones) and returned to MN from a 7000 mile trip through the SW averaged 13.2 mpg. Use the Tow Haul always when towing. Lots of power and 4x4 keeps me from tearing up the ground when parking trailer or starting from slippery parking spot due to rain or snow. Great tow rig!

[moosetags]

We are going with the snow plow prep package as it is recommended for carrying a truck camper as this package includes a heavier duty front axle. The snow plow prep package also includes wiring to the grill area which would be useful for the electric winch that we are planning on adding.

Brian

[BillTex]

To the OP and brian.
We average ~ 16 mpg with the 7000# AS, ~ 15 mpg with the 3000# TC. Yes, the TC is a huge negative wind drag! Have ~50k miles (the majority towing/hauling…don’t use it as a daily driver…) on the truck now; usually tow at 62/63 mph…maybe 69 mph on wide open roads. Speed does not seem to affect mpg while towing at either of these speeds, much faster and it does. I have got as good as 19mpg towing at 59 mph…but I can’t go that slow...drives me crazy! With the TC, I keep it down to 63 mph max. Interestingly, we get the best mpg at ~ 73 mph when unladed (22mpg and as good as 24 mpg on some trips). Diesel attain peak hp at ~1800 RPM…peak efficiency is either side of this, so keep this in mind when you get yours. I have some hp/tq/efficiency curves somewhere. I can email if you want them. (I still haven’t figured out how to post .pdf’s on this forum?!) Speed is often the factor most ignored for best efficiency.

But anyway…get the high idle, think of it as a “choke” for diesel engine. Helps warm the truck up when cold. It can’t really be used for idling or PTO as it shuts itself off when the engine reaches temp. I leave mine set to “on” all year…it does nothing when over 32 deg F…and kicks in the winter time. It is a set/forget kind of thing.

IIRC all diesel have dual batteries (24 volt glow plugs?), and all Duramax have the block heater…which I have used once and found unnecessary, and we have had the truck routinely in weather as cold as _30deg F.
We have the LT3 package, and IIRC a lot of this is included.

Cut/paste from our 06 owner’s manual .pdf;
Elevated Idle/Exhaust Restrictor
The engine has a cold temperature high idle and exhaust
restrictor feature which elevates the engines idle speed
from 680 to 1200 rpms, and restricts the exhaust gas
flow, when outside temperatures are below 32°F (0°C),
and the engine coolant temperature is below 150°F
(65°C.) This feature enhances heater performance
by raising the engine coolant temperature faster.
For pickup models, this feature can be turned off and
on using the DIC steering wheel control buttons. If your
vehicle is not equipped with the DIC steering wheel
control buttons, do the following to turn on this feature:
1. Turn the ignition to RUN, with the vehicle off.
2. Press the accelerator pedal to the floor and hold
while quickly pressing the brake pedal three times
in less than eight seconds.
3. Release the accelerator pedal and start the engine.
When the engine is started, it will slowly ramp up to the
high idle speed after a delay of a few seconds up to
approximately two minutes. For this method to work
properly there must be no throttle or brake pedal faults.
The engine idle speed will return to normal once the
following conditions are met:
• Once engine coolant temperature reaches
150°F (65°C).
• Air intake temperature reaches 32°F (0°C).
The high idle speed will be temporarily interrupted
and the engine speed will return to normal if any of
the following conditions occur:
• The brake pedal is applied.
• The accelerator pedal is pressed.
• The automatic transmission is shifted out of
PARK (P) or NEUTRAL (N).
• The clutch pedal on the manual transmission is
pressed (pickup models).
• Vehicle speed is detected.
Once these inputs are removed, the engine idle speed
will slowly ramp back up to high idle after the normal
delay, if the conditions for engine coolant temperature
and air intake temperature are still met.

As far as T/H; it’s there…use it. The engine braking alone is worth it. Brian, you will love the Duramax/Alli, they practically drive themselves, they are that good. The confidence when towing is just something you have to experience. I don’t get excited about 4 wheel vehicles too much these days, I still very much enjoying loading up and hitting the road with this truck.
Can’t you beg/borrow/steal some time behind the wheel of someone’s Duramax lash up? You will love it…there must be someone nearby.
Good luck.

Bill

[moosetags]

Bill, thank you for this information.

Brian

[moosetags]

Along the line of Dmax fuel mileage, I am looking seriously at the Titan replacement fuel tank for the new truck. In the version for a Dmax Crew cab Long bed, the Titan replacement tank has a 60 gallon capacity. They are kind of pricey at $1000 plus installation, but that is an additional 24 gallons of diesel. That would give me a fill up range of between 750 and 1,000 miles. That sounds like it could be worth the extra money. I would think that a long fuel range like this would give me the opportunity to shop out the best fuel prices in the different areas.

I would like to hear opinions on doing this, especially from someone who has one of these tanks.

Brian

[AirsDream]

I see you wrote to jfscheck about his Titan tank. Transfer Flow also makes one, as do others. Several threads on this, as I recall.

If you're far enough off road and into the rocks that you need the winch, you gotta' be real careful - these oversize tanks get that wey because they all stick down below the frame rails, and I see that the Titan skid plate is high molecular weight polyethylene. No idea how that does scraping over rocks, but if you manage to poke a hole in the tank, you've just created an open drain for your fuel tank, maybe a long way from anywhere. My truck and its predecessors spend/spent quite a bit of time off road, doing farm duty, getting to rivers for fishing, etc. ... and I've managed to seriously bash steel skid plates - to where they had to be torch heated and bashed back into shape with a BIG hammer. Would plastic be better? I have no idea and no personal experience. It might slide over rocks more easily ... I STRONGLY recommend a High-Lift Jack or equivalent. There's nothing much worse than getting high-centered several miles from the nearest road. Sometimes a winch won't help you, where a relatively cheap jack will. Been there. Done that. Made for a bad day.

I thought about a bigger tank, just to get more distance between fill-ups, but after talking it over with some serious off-roaders, I think I'd like to have one that pumps into the regular fuel tank on demand ... but most (all?) of these sit in the bed, just where your camper'll be ... hmmmmm.

Probably no magic solutioin here. Please keep us informed about your thinking and progress on this. Inquiring minds want to know.

[HowieE]

I have a friend living in Pa with grand kids in Va. He has an additional 100 gallon tank on his D Max and never buys fuel in Pa. Savings can run as high a $.50 a gallon when he buys in Jersey or Va.

He also back fills his Jetta diesel from that tamk.

[cyclebloke]

Brian,
I have a 2009, Chevy Duramax LTZ, crew cab, short bed, 4x4, Banks exhaust, Transfer Flow mid-ship replacement, and Air Lift.

I've towed a loaded 25ss cross country three times with a motorcycle in the bed, water toys on top and so much gear stuck in it I don't have room for a passenger.

For mileage I plan on 12.5 at 65 mph. Wind, hills and speed effect the figure. Over 65 mph my mileage usually drops quickly. In Ohio I can get 15 mpg. Same with southern Cal. Northern Michigan it can drop below 12.5 on hills alone and even lower with strong head winds out West.

Most people in the northern climates use the high idle option when it's cold to heat the truck up faster. Diesels take longer to heat up the cabin up and it can be quite noticeable on very cold days. Heated seats help greatly too.

I went back and forth with the fuel tank replacement. Same rationalizations others mentioned. I absolutely love it for the convenience alone. My '09 came with only a 26 gallon tank and stopping so often was annoying, very annoying. It's increased my range immensely. An aftermarket tank will mess up your computer functions pertaining to miles remaining until empty. Some people get hung up on this, but I reset my gallons used function at each fill up and it's VERY close to what i put in at the pump. As mentioned, I bought the tank for convenience, I can't see driving long distances to get better prices as having a payback unless you live next to a border and ten miles a way fuel is substantially cheaper. My time is worth something too.

BTW, I went with the Transfer Flow because it seems to have the best reputation and I found far more info on it than the Titan. I'm not making judgement on the Titan. The Titan will definitely require a skid plate.

The newest Duramax's come with a 36 gallon tank. My advice here is to try it and see how it goes. You can add a tank at any time. My aftermarket tank sits 2 inches below the frame, but it's not the lowest point. For reasonable off roading I'm not concerned. Off roading means different things to different people. For truly serious off roading a long wheel based 2500 wouldn't be my choice to start. Again, a lot of subjectivity here.

For the set up you are envisioning, the Duramax is a nice no excuses rig. I bought mine to tow my boat which is heavier than my AS and doesn't have weight distribution. Unless you tow all the time over several hundred thousand miles, the cost savings in fuel alone will not pay for the diesel/transmission option. The beauty of diesel is torque and you will rarely be lacking. The biggest problem you'll have is keeping your speed down.

Enjoy!

[moosetags]

Thanks for all the input. I really appreciate the views from a different direction.

Our off roading consists of mainly dirt roads that are narrow and sometimes muddy, sandy, or snowy. We don't intend to try any rock crawling with a pick-up truck that has the wheelbase of an aircraft carrier. We do mainly forest roads in pursuit of Mooses. We are also planning to do some ghost towning. Some of these require covering dirt roads with sand traps. We do plan to add a winch to the new truck to help us out when necessary. We could have used a winch yesterday to get a fallen tree off the road. Instead, we put a tow rope on the tree and were able to pull it out of the way with the Suburban.

The fuel tank thing will require a replacement fuel tank as our truck bed will be totally occupied by the truck camper.

Thanks for the info on the Transfer Flow metal tank. I will look at that one closely.

I do plan to go with the 36 gallon OEM tank for a while, and see how it works out for our travel style.

Brian

[newroswell]

From FAQ?s for TITAN Large Capacity Replacement Diesel Fuel Tanks:

Q: Is the TITAN Fuel Tank as durable as the original stock equipment tank?
A: More durable and better warrantied. Most stock (or original equipment) tanks are relatively thin and made of materials like Linear Polyethylene. TITAN Fuel Tanks are made of High-Density Cross-Linked Polyethylene (XLHDPE), which is bonded molecularly. Also, the nominal thickness of all TITAN Tanks is ¼ of an inch. TITAN Fuel Tanks are so tough that they are backed by a 5-year, or 50,000-miles, limited warranty.

If you're going to get in the rocks, you'll want to make or have fab'ed up a whole slew of skid plates to protect things that aren't protected very well by even the factory Office-Road packages.

[moosetags]

Originally Posted by newroswell

From FAQ?s for TITAN Large Capacity Replacement Diesel Fuel Tanks:

Q: Is the TITAN Fuel Tank as durable as the original stock equipment tank?
A: More durable and better warrantied. Most stock (or original equipment) tanks are relatively thin and made of materials like Linear Polyethylene. TITAN Fuel Tanks are made of High-Density Cross-Linked Polyethylene (XLHDPE), which is bonded molecularly. Also, the nominal thickness of all TITAN Tanks is ¼ of an inch. TITAN Fuel Tanks are so tough that they are backed by a 5-year, or 50,000-miles, limited warranty.

If you're going to get in the rocks, you'll want to make or have fab'ed up a whole slew of skid plates to protect things that aren't protected very well by even the factory Office-Road packages.

Thank you for this info. I have been looking at both the Titan and the Transfer Flow. Both seem like quality products, and the prices are comparable. I guess it will be a matter of deciding on plastic vs. metal. The Titan that I am looking at has a 4 gallon higher capacity (60 vs. 56), so I think that this will be a consideration, also.

Brian

[moosetags]

I have been wondering what are the Dmax service intervals in the real world. With the Suburbans , I have always been guided by what the DIC (driver information center, a somewhat unthinking acronymal choice) says. I have them serviced when the DIC drops to below 15% engine oil life remaining. This has usually been between 5 and 6 thousand miles, depending on conditions.

With the Dmax, should I depend in the DIC, or go a different way?

Brian

[TinCanLand]

Anyone using the 4.11 rear axle?

[redeagle313]

Originally Posted by moosetags

I have been wondering what are the Dmax service intervals in the real world. With the Suburbans , I have always been guided by what the DIC (driver information center, a somewhat unthinking acronymal choice) says. I have them serviced when the DIC drops to below 15% engine oil life remaining. This has usually been between 5 and 6 thousand miles, depending on conditions.

With the Dmax, should I depend in the DIC, or go a different way?

Brian

I would go by the DIC. There are people out there who change their oil at 5000 miles or earlier with diesels, IMO that is a waste of money. Many owners (who use their trucks in business) use oil analysis to determine whether they are changing too often or not often enough.

I have been going 7500 miles on oil changes, which is what the '07 DIC hits 0%. I have been changing the fuel filter at 12,500, which is when the DIC hits 0%. (changed the spin on Allison filter at 5000 miles) The dealerships are usually price competitive on the oil change and tire rotations, but they WAY over charge for the Allison filter and the fuel filter, to say nothing of their labor charges. Easy DIY info available on the Dieselplace.com.

I have always used Stanadyne Performance Formula additive.

[BillTex]

Originally Posted by redeagle313

I would go by the DIC. There are people out there who change their oil at 5000 miles or earlier with diesels, IMO that is a waste of money. Many owners (who use their trucks in business) use oil analysis to determine whether they are changing too often or not often enough.

I have been going 7500 miles on oil changes, which is what the '07 DIC hits 0%. I have been changing the fuel filter at 12,500, which is when the DIC hits 0%. (changed the spin on Allison filter at 5000 miles) The dealerships are usually price competitive on the oil change and tire rotations, but they WAY over charge for the Allison filter and the fuel filter, to say nothing of their labor charges. Easy DIY info available on the Dieselplace.com.

I have always used Stanadyne Performance Formula additive.

Agree...DIC is there for a resaon. I run Rotella full syn..get it at Wallys.

DIC tells me to reboot somewhere around 8k-10k. I do the fuel filter at the same time...even though it always has some life left to it...
I also changed the Alli filter once early on.We are going cross country again this year so I will do it again. Time for new tires also...

BTW Brian; what load rating are the tires on the new truck? You will want at least 123...

Bill

[moosetags]

The tires that I have ordered for the new truck are the all terrain black walls. I do not have any further specs. I am hoping that GM will put adequate load range tires for the truck's 11,600# GVWR.

Brian

[BillTex]

Originally Posted by moosetags

The tires that I have ordered for the new truck are the all terrain black walls. I do not have any further specs. I am hoping that GM will put adequate load range tires for the truck's 11,600# GVWR.

Brian

Hmmm...anyone know what the 2011 GM 1 tons are coming through with?

There are "adequate" tires and then there are "more than adequate" tires...

I would assume the 1 ton comes through with something rated at least 123...but it is possible they are 120's....I would try to find out and make sure you get at least 123 service rating...

I guess the point is; don't let tires be a weak link in a brandy new truck...you will be heavily loaded, and want the best of everything...

Again; I would assume 123 SR on a one ton...but I would ask....

B

[moosetags]

I am trying to check this out now.

Brian

[Mikethefixit]

Brian
You ask about oil change intervals. I being an old trucker and have millions( I lost count) of miles behind desiel engines. I only change every 10k miles as I did with the big trucks. I change everything. AIR,FUEL and Oil Filters. I use SHELL ROTELLA T 10-40 also as I have for years. I just changed at 90k miles. The oil was right on the full mark, I have not added between changes. SO my 10 year old 7.3 Harvester uses NO OIL. NO RUNS NO DRIPS so far.
GOOD LUCK With YOURS.
ROGER