Want up to 20% Better Fuel Economy?
Updated: Apr 1, 2021
Can a transmission lockup kit really save you fuel?
The primary reason for installing a MM4X4 lockup kit is to protect the transmission from high temperatures when working the transmission hard; such as when towing or in deep sand.
Temperature is the No. 1 killer of your expensive transmission.
But a lockup kit also has other benefits, such as fuel savings, the responsive 'manual gearbox' like feel of the car, and lower EGT and intake temperatures - all because the car doesn't need to work as hard.
How does a lockup kit save fuel?
The torque converter of your transmission is a fluid coupling between the engine and the rest of the gearbox, and the fluid is the transmission oil (or ATF). Because it's a fluid coupling it can only be, at most, 90% efficient as there would always be some slip. This slippage uses more fuel and creates heat!
This is why modern automatic transmissions also have a lockup clutch in the torque converter. When activated there is direct mechanical coupling between the engine and gearbox, which is designed to save fuel by eliminating the slip.
This is also the reason why published manual gearbox fuel economy figures are always better than the automatic’s figures, ie, no slip!
MM4X4 lockup kits use advanced digital CANBus communication with the vehicle ECUs to more effectively engage the lockup clutch.
Put simply, when the torque converter is locked it saves fuel.
How much can you save?
The lockup kit saves fuel when it locks the torque converter when the factory ECU program would otherwise have it unlocked.
So how much fuel you save depends on driving conditions and your model of vehicle. Some people have reported 20%, which is certainly achievable.
We like to set realistic expectations on what's a typical fuel saving (10-20%)
If you drive on a highway in 4th gear at 90-100kph, the factory ECU will generally lock the torque converter for optimum fuel use. But, use 5th gear (or DRIVE), and you’ll use about 10% more.
Where fuel savings with our lockup kits really step up is when you're not in those favourable highway conditions.
Climbing mountains, driving into head winds, larger tyres, or winding, hilly roads are other times when the lockup kit will certainly save you more fuel. And if the conditions are right you may be able to select 5th gear (locked) at 80+ kph and save even more fuel than normal.
We claim 10-20%+ fuel savings. 10% is a typical result when touring with a caravan behind a Pajero or Prado. 20%+ has been reported by several Challenger/Triton customers, as these models have a high slip torque converter in order to achieve the claimed 3T towing rating from the 2.4L engine.
One customer in a highly modified Triton (MN) reported going from 22L/100km, when regularly towing across the Great Dividing Range in Queensland, down to 15.5L.
That Triton was getting a 6.5L/100km (30%) fuel saving... massive.
We only stand by figures if we have evidence. So while we had the opportunity with a Challenger we did a quick apples-for-apples comparison as a demonstration of what might be achievable.
Let’s Conduct a Fuel Comparison Test
Vehicles which achieves great fuel savings are the Landcruiser 200 the Challenger, and it's cousin, Triton (MN). While making some improvements to the Challenger auto-mate we took the opportunity to do a quick fuel comparison test. The vehicle was stock apart from typical 4WD accessories like a lightbar, smartbar and drawers. We were not towing anything.
We then followed up this same test with our Landcruiser 200 series (2016 facelift version).
The route was a typical country touring route with a mix of winding roads and straights with speeds ranging between 40 to 80 kph and one steep 3 minute climb. On this route the factory ECU would rarely lockup the torque converter, so it provided a great comparison of the fuel economy difference when using a lockup kit like auto-mate and lockup-mate PLUS+
The route would be driven twice in a similar manner with the lockup kit both ON and then OFF for a direct comparison. auto-mate (in the Challenger )was used in DRIVE, and lockup-mate PLUS+ (in the LC200) used in S4.
The route was driving in a clockwise direction and took 30 minutes to complete. (On this route we didn't do a turn around at #671, so ignore the 50 minutes and 45km on the map)
We were after a relative comparison so we used the fuel economy meter in the centre displays of the Challenger and Landcruiser. They were reset at the start of each run and recorded at the end. We also logged the transmission temperature for comparison.
TOYOTA LANDCRUISER 200 (2016)
lockup-mate PLUS+ OFF 16.8 L/100km
lockup-mate PLUS+ ON 14.4 L/100km
MITSUBISHI CHALLENGER (2012)
auto-mate OFF 13.1 L/100km
auto-mate ON 11.2 L/100km
That's a fuel saving of 2.4L/100 in the Landcruiser and 1.9L/100km in the Challenger - and we weren't even towing!
Now, there are two ways to report this statistic:
How much more fuel did the factory ECU program use compared to auto-mate/lockup-mate, which is 2.4/14.4= 17% (in the LC200), and 1.9/11.2 = 17% (in the Challenger), or
How much fuel did lockup-mate/auto-mate save compared to the factory ECU, which is 2.4/16.8=14% (LC200), and 1.9/13.1 = 14% (Challenger)
Either way you look at it, 17% (or 14%), is a substantial fuel saving.
So with this example, driving a typical 20,000km/year in the Landcruiser and Diesel at $1.40 is $672 per year ($532 for the Challenger)
When saving $672 per year it won't take too long for to pay itself off.
This test was more about fuel comparison than temperature, but the temperature results are below for interest even though we weren't towing.
In the Challenger the average transmission pan temperature was 21 deg C cooler and 10 deg C in the LC200. Lower temperatures protect the transmission and also extend the life of the transmission oil. .
Notice how in the first 10 minutes, lockup-mate PLUS+ and auto-mate were cooling the transmission oil during the uphill section whereas when OFF the temperature increased.
So, an MM4X4 lockup kit can certainty save fuel while it protects your transmission from heat.
Checkout our website for more details
Marshall and the MM4X4 team