Ahh, another heated discussion amongst the diesel community, LML vs L5P. Often we see the comparisons amongst manufacturers but this is just between passionate Duramax fans. With six different Duramax engine models to potentially compare, this recent argument resides between the two most recent models. The LML Duramax was the power house for almost six years(2011-2016) when the L5P was released in 2017. While the LML seemed to be the “best” duramax to date there has been a serious disturbance since the release of the L5P. We will now look over both the LML and L5P to see how they compare(plus we found a cool video we added at the end). Is there a new king, lets see…

LML vs L5P: Horsepower

When the LML Duramax was released in 2011 it received an additional 32 horsepower over its predecessor the LMM. At the time not many people were blown away by the increase in horsepower(365hp vs 397hp) or a 8 percent increase in power. But looking back at the previous model transition we only saw a 5 horsepower gain(360hp vs 365hp) or 1 percent gain. Now comparing it this way we see that this is a very significant power increase.

With the release of the L5P, GM decided they were going to make a statement by adding 45 more horsepower to the new Duramax. This increase in power was the biggest percentage power increase since the LLY to LBZ models(16%). The increase in power from the LML to the L5P is a 12 percent horsepower increase that is very noticeable. Having driven both an LML and L5P with similar specs the power output is a night and day difference.

Horsepower Winner: L5P

LML vs L5P: Torque

On to the power rating that matters most to those that tow a lot, torque. Torque is the brute force that allows towing of massive loads from one place to another. The more torque you have often means the more weight you can tow.

The LML features a torque rating of 765 lb ft which is a 16 percent increase over the previous LMM model(660 lb ft). This was a large power increase and was well received among heavy haulers. The respectable torque of the LML carried the Duramax for 6 years before the heavy hitting L5P was released. When the L5P was released in 2017 it brought with it some major torque, 910 lb-ft to be exact. I feel that this high torque gain was brought on to stay competitive with Ford and Dodge, but we will talk about that at another time. So the increase in torque for the L5P was a staggering 19 percent! The winner for this category is clear but don’t underestimate the LML as it is powerful in its own right.

Torque Winner: L5P

LML vs L5P: Gas Mileage

Great gas mileage doesn’t usually come to mind when talking about trucks. With the amount of power previously mentioned it also shouldn’t be expected. In fact auto manufacturers are not required by the EPA to post or publish fuel economy numbers for 3/4 and 1 ton trucks.

With all that being said this comparison will strictly be based on user experience. Measuring of fuel economy can be swayed by many factors so take this for what it is. Based on user data from Fuelly, the LML and L5P are almost tied with an average fuel economy of 14.5. Now this isn’t scientific testing but it does give us a good feel for what these trucks are capable of.

Fuel Mileage Winner: Tie

LML vs L5P: Aftermarket Add Ons

The vast majority of truck owners will add at least one after market item to their vehicles. While most will add as little as window tint others will do step bars, light bars, lift kits and more. The trucks themselves are almost identical which would allow for suspension parts and other bolt ons to work on both trucks.

The big difference would be that the LML and L5P are completely different engines. The LML has a abundant amount of performance upgrade options available from custom tuning to cold air intakes there’s not much you can’t do to the LML. Another favorite modification of LML owners is to delete the emissions systems from the trucks. By removing the emission components these trucks are able to eliminate the need for DEF, push more power and get better gas mileage.

The L5P at this point in time has not yet been hacked. It features a unique ECM that is causing problems for custom tuners. By not being able to “hack” the computers for the engine owners of the L5P Duramax will be unable to delete emissions items as well. One of the major draws to diesel powered trucks is the ability to boost power as much as 150 horsepower for under a $1000. The same horsepower gain for a gas powered truck would need 5-7 thousand in performance upgrades.

Aftermarket Add On Winner: LML

LML vs L5P Overall Winner: L5P

Now that the battle is over we are left with some obvious wins but we should also consider the intentions for the truck. The obvious winner for a stock truck is hands down the L5P as the power numbers are insane. But if you are looking to push your diesel to the limits and remove troublesome emissions components than the LML is for you.

The thoughts and opinions expressed in this article do not directly reflect opinions of all Intense Diesel staff

Video: LML and L5P Dyno Comparison

The YouTube channel “Built 05 STI” filmed a L5P dyno run as well as a LML dyno run and compared the two, check it out!