Skirmich

Hi folks!

This is a little post about my current MPG performance and some discoveries I made about getting the most mileage.
First of all, I am in no way dissatisfied or surprised by my X MPG performance I knew before hand the 3.7L was a thirsty engine and that I would struggle in the city with it. I think its fair for some guys to be let down by the poor mileage in some cases.

My Current Setup.
87K
K&N Filter (Should not make a difference)
NGK IR Laser Plugs
Mobil 1 EP 5W-30 for Engine
DW-1 for ATF
Mobil 1 LS 75W-90 for Transfer
DPSF AWD for Rear Diff Fluid

My Current Mileage (Flat Roads) and All results are Manual calculations not MID and 2 or 1 people load with light cargo:
Highway @ 60mph = 26mpgs < Pretty Happy about this
Highway @ 70mph = 22mpgs < Still somewhat happy
Highway @ 80mph = 19mpgs < Not so happy

City No Traffic @ >60mph = 18mpgs
City No Traffic @ >50mph = 17mpgs
City No Traffic @ >40mph = 16mpgs

City w/traffic @ >40mph = 16mpgs
City w/traffic @ >30mph = 13mpgs
City w/traffic @ >20mph = 11-9mpgs

This is about what I was expecting more or less for the MDX with the 5 speed. Now to my discoveries.

First of all. Automatic mode (D5) is HORRIBLE, Way too much engine brake gets in the way all the time even on highway you can be cruising comfortably and at a light touch of the brake it will auto downshift way too early in the brake pedal travel. This is more notable on traffic were engine brake is usually there below 40mph which is ridiculous. Then when accelerating the engine will just upshift too fast making the car heavy and needing to push the gas pedal further down to compensate. I was under the impression that if I made the engine not pass 2.5K RPM I will be maximizing my MPGs but boy I was wrong... The MDX needs to get to speed and fast to take advantage of OD Gears.

My discovery.. Using SS for Daily Driving.
This might sound insane but please hear me out.
SS does not allow engine to brake at all, SS will only downshift when the RPMs are too low and the engine will stall so there is absolutely no Automatic Engine Brake on SS. This got rid of all the unnecessary downshifting in the traffic at low speed thus helping MPGs already.

Also another point..
The DBW does not store driving habits while using SS, So you can drive all Toretto Style on SS and still keep the Grandma Mode on D5. Like a Sport & Eco Mode although given my results D5 is not more efficient than SS.

Acceleration. Usually in D5 if you wanted to accelerate fast 1st gear will hold up way too much around 4K depending on how much acceleration you want. But since 2nd gear and 3rd gear are so closely matched ratios you can shift on 2nd earlier (This will reduce momentum but will keep the acceleration smooth) so by shifting 1st around 3K > 2nd around 2.5K > 3rd around 2K I got all the acceleration I wanted to immediately shift into 4th or 5th (Around 45mph) to start saving MPGs. I tried this mode for about a week in a here are the results:

City No Traffic @ >60mph = 24mpgs
City No Traffic @ >50mph = 21mpgs
City No Traffic @ >40mph = 19mpgs

City w/traffic @ >40mph = 19mpgs
City w/traffic @ >30mph = 17mpgs
City w/traffic @ >20mph = 16-13mpgs

The difference between D5 and SS has been seriously notorious in the city MPGs.. I went from struggling to get 15mpgs at below 40mph to constant 18-19mpgs, This was mainly because the car will upshift way too fast and overload the engine..

My main tip is.. Get to 40mph as smoothly and fast as you can.. DO NOT build speed slowly this is what destroys MPGs and try to avoid D5 as much as possible do not use SS as a "Performance Shift" rather than a more efficient "Automatic Plus Mode".

mrgold35

I'm going to give this a try in a few weeks when I head to Las Vegas for a long weekend. I can never seem to get above 15 mpg in that city. I might even try SS mode on the hwy because the 6AT does a lot 1-2 gear downshifts on hills when it might stay in 6th with a little more gas. I'm sometimes 3 1/2 - 4hrs between gas stops on the hwy and any extra mpgs would help.

Skirmich

Yeah I have a calculation using the SH-AWD monitor to know how efficient I am driving in highway.
basically if the front wheels have 2 blocks I will get below 22mpgs. If I can manage the throttle to keep 1 block in the front and 1 block in the rear I will get +25mpgs.

So:
+25mpgs
----0-0----
----0-0----

VS
-22mpgs
--00-00--
----0-0----

VS
-19mpgs
--00-00--
--00-00--

VS
-17mpgs
-000-000-
--00-00--

RDX10

Wow, I love this. It is very awesome how you broke it down even by shawd functionality!

Skirmich

I need to keep myself occupied in the long stretches and do these experiments as a pass time, I rarely use the car in this way so these MPGs are basically the results of these experiments not my daily results

This all started because the on board computer is very basic and lacks a lot of functionality specially knowing the load of the engine so I starting using the SH-AWD MID Screen to know how much power is being used so I could drive even more ECO.. Watching its behavior on D5 at low speed also pointed me to try SS instead and visually confirms that I used less power by shifting myself.

csmeance

The mdx is supposed to cut fuel to the injectors when you let off the gas causing engine braking, in SS it doesn't shut off the injectors as far as I've read/known.

Skirmich

^ That happens in almost every new car. But the main issue was the automatic downshifting making me lose too much momentum which then I needed to gain afterwards by accelerating. So in SS I can barely slow down by letting off the gas when coming to a stop, let it coast and wait till it turns green so I don't use too much gas to regain my speed.. In normal D5 conditions I let off the gas and the car will downshift sooner even if I am not going downhill the car wont downshift like it does on SS.

RDX10

I think this has to do with the transmission being 5-speed. The ratios can't be spread too far or too close with 5 gears, but I remember in my rdx that the gears were all spaced pretty close and it was easy to get to 5th gear at normal city speeds.

So what you are saying is that leaving it in manual mode allows you to keep the engine in the highest gear possible which lowers rolling resistance allowing you to coast longer at lower rpms right?

One more thing, in post 4 you mentioned how if you put your foot on the throttle in a specific way, you could force the shawd to run in 100% fwd as per the mid. My rdx was the same thing, it was always running in 50/50 as per the mid but if I just barely feathered the throttle, I could get it to run in 100% fwd.

Skirmich

There is no possible way to make the car truly 100% FWD the minimum SH-AWD can go is front 90/10% rear that is why SH-AWD is considered a Full Time AWD as it cant never disengage the rear axle.
MID wont show you that ratio as:

0000-0000
----0-0----

This is the minimum you can drive and the best MPGs:
----0-0----
----0-0----


What I use the SH-AWD screen is to measure the Torque given, So more blocks = more gas.. The less blocks you see the more eco friendly you are driving..
So in the city I use SS to try to REV-Match the gears in 1 through 3rd gear, This reduces load in the engine and allows you to get into OD gears faster.. 5th gear can be shifted around +42mph but you need have lots of room to cruise comfortably at very light throttle touch (You can even set Cruise Control at those speeds and force 5th), This is completely doable and the best way to achieve high MPGs in the city. If you let D5 take over you are NEVER going to see 5th speed until +50mph.. This is mainly because the stupid DBW Habits feature and the ECU programing so you are cruising along at 40mph at 4th gear which makes the RPM hit 2K all the time.. Speed up a little more in SS to 42-45mph and hit 5th gear to make the RPM hit as low as 1200RPM with TC lock up and around 1500 with TC unlocked this will give you maximum MPGs in the city and when its time to reduce speed you are never going to hit Engine Brake.. SS will only downshift to prevent Stall so its basically downshifting at idle speed, This gives you maximum coast speed and duration.

Skirmich

Obviously driving like that ^ Its miserably and takes out all enjoy in driving the car....
Use it when you aren´t in Brian O´Conner mode and want to save all the Gas you can..
REV-Matching (I don´t know the exact RPMs I just feel it when shifting):
1st - 2500-3000RPM
2nd - 2000-2500RPM
3rd - 1500-2000RPM
Then
4th - +35mph
5th - 42mph

RDX10

Absolutely! I had a 2004 touareg V6, averaged 14mpg and I would always drive in manual mode with upshifting as soon as possible and putting it on cruise control on 6th gear. The touareg had 6 speeds, but it would also hit 6th when around 42mph.

It sucks when a vehicle is let down with a shitty transmission.

ALX2987

Thank for this, Ive noticed the engine braking and seemingly excessive shifts by the auto. I've been driving stick for the past few years so I didnt know if it was just being overly sensitive or if there was an issue. I'll def have to check out using SS

Skirmich

Your Welcome! I have been driving my MDX fully on SS most of the time now.. I find full auto very sluggish (trying to save MPGs it Upshifts too early) so I stuck with SS 24/7 now and I´ve been very impressed with the "Hidden" performance of the X.
Obviously this doesn´t go hand in hand with MPGs but XMAS time I hardly have time to Hipermile... Will come back with new Information after I adjust my valves when I hit 100K.

ALX2987

Exactly, it shifts way too early, to the point where it bogs the engine occasionally. I need to get used to driving the X, and learn how it drives best. With my Legacy, obviously a very different car in every aspect, I was pretty much giving slight accelerator adjustments constantly, and this would greatly effect speed, and mpg ( it had a needle on the dash, and a read out in the display which gave real time mpg) but with the X, I've noticed I need to get into the gas heavily to get it moving and/or increase speeds on the highway. With smaller accelerator input, seems to confuse the transmission and just upshifts without any real increase in speed. Is this consistent with your driving experience?

Skirmich

Yep this has to do with the STUPID DBW (Drive by Wire) Logic..
The MDX will adjust to your driving behavior which seems to me always stuck on "Lets make MPGs" mode so the MDX will bog down upshifting too early making it feel slower than what it is... You can Reset the DBW Logic by disconnecting the battery (Always brings a smile on my face) and it will drive like it has a 300HP engine again but it will go back to "Lets make MPGs:" mode in no time so the satisfaction doesn't last long enough.

You can get the SPRINT BOOSTER system to remove the parachute effect of the DBW Pedal but it will run you down 300? bucks and it will obliterate your MPGs as it makes the ECU Believe you are pressing the Pedal Harder (Basically it just makes the Pedal Travel range Lower). So with Stock Pedal range of say 15% with the Sprint Booster is something like 25-30% input to the ECU.. Obviously this means the Sprint Booster removes some of the lower range Input to make the DBW Pedal more responsive.. At least it has 2-3 modes on it so you should be able to go back to stock anytime you want by pressing a button.

ALX2987

Interesting, I will have to look into that booster, although I cant imagine the mpg getting much worse...

I've been using the sport shift occasionally since I've had it, (a whole 3 weeks) and it definitely drives a bit better, but good god is that shift slow lol