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6.6 LML Duramax vs 6.0 Vortec Musings


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Since I have benefited from and have sincerely appreciated many of the valuable posts on this forum, I thought I would share my experience with gas vs diesel GM trucks.  As a little background, I am not a mechanic or engineer.  I have a farm and construction background and work in a seasonal climate in the Midwest.  I have owned many different makes and models of both gas and diesel cars, trucks and heavy equipment – mostly John Deere and Caterpillar.  

I started out many years ago with gas engines (first was a 400 small block in a 78 GMC) and have primarily owned GMC or Chevrolet, but also have had a couple of Ford trucks and a Toyota Tundra.  I have very little experience with Ford diesels except for one 88 Ford with the 7.3 diesel.  I have had several 6.0 gas motors and five different Duramax diesels – a 2003, 2007, 2008, 2012 and 2015. 

 

My comments here focus on the recent differences that I have noticed between the 6.0 Vortec and the 6.6 LML Duramax.  I am not writing this to stir the pot or to make anyone angry – but rather, to share my experiences and thoughts about the subject.

As background, I recently owned a 2012 6.6 Duramax that I recently sold with around 110k miles and then purchased a 2014 6.0 Vortec flex fuel.  I liked the idea of being able to pump ethanol or E85 and have one local station that sells E85; I also like supporting the farm economy, but I am not wanting to debate the emissions issues related to ethanol – it’s too political for this forum – smile!.  I also recently purchased a 2015 6.6 LML Duramax.     

 

I will admit up front that I have a diesel bias.  I have been around diesel engines since I was a kid and enjoy how they operate and the extra torque they generate.  With that said, I also know that the gas engines can play a vital role in many situations. 

 

Summary of the 6.0 Vortec.  The Vortec is a very sold and reliable engine in my experience.  It also is fairly easy to work on in this modern era.  Open up the hood and the engine bay is uncluttered and almost looks like the cars from the 1960’s – the ones you could actually work on!  The Vortec is powered fine for daily driving and is acceptable for light towing.  When it comes to heavier towing, it doesn’t keep up.  As an example, I have pulled a hitch dump trailer with total load with truck/trailer of around 28,000 pounds and the Vortec will handle the load, but when going up hills it really struggles – not to mention the noise it generates when it is downshifting to find a gear with a higher RPM range that can generate the torque needed to pull the load.  With respect to fuel economy, the Vortec averaged around 12.4 mpg on E85 over a 3,000 mile stint and around 13.6 on 87 octane gas over roughly the same miles.  I also played with an aftermarket tuner and didn’t notice any significant mpg change or power change, but also didn’t have it dynode (I will avoid mentioning any tuner names since that is not the focus of this post).

 

Summary of the 6.6 Duramax. The LML Duramax is also a very reliable engine and the Allison transmission is very strong, but the engine bay is very cluttered and even if you do an EGR delete, you will find it difficult to work on it like you would a 1967 Camaro.  The Duramax is probably overkill for the joy-ride driver, but is almost a necessity for the daily hauler/puller.  The Duramax has plenty of power for most light and heavy pulling applications.  I have pulled both 5th wheel and drawbar trailers with ease in the Duramax – and unless you have removed the exhaust, you will not notice the engine noise nearly as much as the Vortec when pulling up an incline.  The same 28,000 lb load referenced above is not hard on the Duramax at all.  The Duramax also has the exhaust brake starting in year 2011 that comes in very handy when towing.  The tow/haul or trailer mode on the Duramax is much more sensitive as compared to the Vortec’s transmission trailer mode – frankly, I thought the Vortec trailer mode was a joke, it didn’t seem to do much for the truck when slowing down with a load.  The Duramax also will obtain decent fuel economy – I have averaged around 16.6 in town driving without pulling and around 18.5 on the road without pulling and with no tune and a stock motor.  Of course, if you want to upgrade your Duramax you can easily increase the mpg and/or torque/hp rating with or without emissions deletes.  One downside of the Duramax is the complexity of the DPF and need to add DEF fluid.  The DPF/DEF systems add extra components that can/will fail over time.  On the 2012 Duramax I had a DEF sensor went out around 60k miles and sent the truck into limp mode – which was not fun.  The Vortec doesn’t suffer from those emissions issues.  You also will have higher maintenance costs with the engine oil change and the need to change fuel filters on a regular basis.  One-point worth mentioning is that if you purchase a Duramax, your truck will likely benefit from a lift pump installation which will also likely help with fuel filtration depending on your lift pump install.  There are several manufactures to look up and lots of threads on the diesel forums about the lift pump application and benefits. Also keep in mind that the Duramax will likely have better resale value when it’s time to retire or upgrade. 

 

In conclusion, the Vortec and Duramax both have their place and they both are solid engine platforms for either work or play.  If you don’t want to spend the extra money and want less maintenance, then the Vortec is the better option.  If you want/need more power and better fuel economy, not to mention the exhaust brake for towing and the more beefier Allison transmission, and you’re willing to pay more upfront on average for the Duramax and more in maintenance cost, then the Duramax surely will not let you down.  However, be very wary of purchasing one that has been on the truck pulling circuit!

 

 

 

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