Fuel Economy tips and tricks

[Mimic4]

I know it's been done before, and I was reading another thread where OP listed driving habits and people made tips etc, so I was hoping to do the same because I am usually quite an avid "hypermiller" and try to save every drop as best I can, just as a hobby (and all those pennys... I mean nickels add up!).

I usually see the average economy as ~20mpg which is what I was struggling to achieve, but some have claimed tales of close to 30! I want to know what strategies have enabled these numbers or how to get closer!

Currently I am having trouble defeating 17.5mpg, sounds crazy but I'm worried i'm losing her. I'm going to do oil-change, and try to find an easier flow air filter as recommended on previously mentioned thread "Unifilter lifelong foam".

CURRENT VEHICLE STATUS: 220,500km odometer, original heads, recently replaced glowplugs, EGT blocked off, all stock other than that.
Suspected reduction of boost due to waste gate spring age, plan to purchase boost gauge to investigate. (This is my first question, would a reduction in boost reduce economy at higher loads due to fuel/air balancing? -- I admit its hard to tell in the side mirror but I have never, ever, ever, seen any smoke from my tailpipe at all except a brief spurt on a very cold start up)

DRIVING STYLE FOR ANALYSIS:

I never exceed 90km/h but frequent 80 on freeways.

Slow accelerations, I usually never exceed the throttle pedals "half way stop point". You know if you push the pedal down, the point where it stops before it takes a lot more resistance to push it further? That weird spot is slow to accelerate but usually pretty prime spot (or so I believed.)

Keeps the RPM around 2150, and I try to keep it here as often as possible as I believe this is the engines max torque RPM and this is usually close to the peak BMEP.

Tires fully inflated, and VAN is stripped for weight, no rear seats or any cargo.

--Also, I usually put the auto-trans into neutral at stops to reduce van shaking and pressure on the torque converter, but I started wondering if it's more efficient to leave it in drive and hold'er'back with the brake. So this current fuel tank I am leaving it in drive all the time (minus parking duh :P)
I will see if any difference is noted.


That's all I can think of to include but feel free to ask more questions that would help!! I haven't had enough time to grow particularly accustomed with the engine and its more specifically relatable mechanics that would affect fuel economy, I've been in the gasser world a lot longer...

Any advice, tips, solutions, things to try would be very appreciated!

Sometimes you just need a second pair of eyes, THANKS IN ADVANCE! :)

[FalcoColumbarius]

My opinion:

The better the lubricity of the oil in the engine, the better the fuel economy. Currently I'm using Total Quartz 9000 full synthetic (5W40) with a graphene additive by "Power Maxx". Good air flow also helps but you definitely want to protect your motor from crap getting in via the air filter so I wouldn't want to use the K&N filters, myself as I go down dusty roads and I believe they let too much through. I tried a Fram filter element once and my mileage tanked, much like driving with a dirty filter element. The best one that I have used is the Sakura filter elements.

Regarding RPM, my best economy is at 2,600-2,750 RPM, typically between 105 and 110. That's what the IP is dialed into. One time I was working at a place right off the highway and I was starting just off the highway and it was the same every time I took the trip. One week I drove at 80KPH, then calculated my fuel consumption for that week. Next week I drove at 90 and calculated my consumption. The week after that it was 105 ~ by far the best economy. Driving at 80 was my worst economy, out of the three.

I set my tyres at 42 PSI, which I think is the happiest marriage between traction and economy.

Boost works best between eight and nine PSI. Any slower and it's not collecting it's optimum capacity, any faster and though it's spinning faster it's not collecting as much air as between eight and nine PSI.

I took out my stock exhaust pipe and replaced it with a stainless two point five inch mandrel pipe. I haven't noticed a huge difference but logically the engine is going to perform better with the one and a half inch pipe as it creates more back pressure to turn the turbo compressor.

I took the EGR out and my wagon gets ~ I say 30% better economy, runs cooler and has more cowbell.

Typically I get as good as 24 MPG (Imp.); 8.5 kilometres per litre; or 12 litres per hundred kilometres in the city and 34* MPG (Imp.); 12 kilometres per litre; or 8 litres per hundred kilometre on the highway.

Falco.

P.S.: Correction from 36.

[Mimic4]

Wow! Thanks for the quick and helpful reply Falco, I cannot believe 36 on the highway. O.O

I must be doing something totally wrong, I'm in the process now of removing the exhaust manifold (and everything above it) to install the probe for my new EGT. Hopefully it can shed a little light on what's going on inside while i'm driving.

I'm really surprised you found better mileage going FASTER on the highway compared to slower, due the the L300's aerodynamic profile.

If you or anyone has any links to any more information, I would be grateful. I don't know how to check/adjust the IP but I've been reading a lot about it's impact on fueling and thinking if I tweak enough stuff the right way maybe I could have 36 on the highway and not 18...

[FalcoColumbarius]

It does depend on the highway. Eight litres per hundred kilometres would be say on the Number One from Vancouver to Hope, a long straight and constant cruise. The Ninety-Nine ~ Vancouver to Pemberton is not going to be as good as it's more of a winding highway. I'd imagine the fuel economy on the Prairies (no wind) would be stunning. Also, my wagon is a P25W low roof, also known as the "Aero Roof" which may have some bearing on economy over the P35W high roof but we're talking about a five inch difference so I wouldn't think that it would be that great a difference.

A leak in your air intake system will create a loss of power and poorer fuel economy, as will a leak in your exhaust manifold. One of the biggest offenders to fuel economy and performance is a dirty air filter element. I've seen guys tear their turbos apart but still have a two year old mid grey coloured air filter element. Typically, start with the simplest and cheapest trouble shooting is my philosophy.

One question for you is what kind of tranny do you have? When I drive with my automatic transmission I drive at eighty kliks and I'm at two grand. At one hundred kliks my RPM is at 2,600. With a manual tranny a hundred kliks is more like three thousand RPM. Where I've driven manual Starwagons, I haven't driven them long enough to measure the fuel economy so I'm not sure how their IPs is dialed in, &c..

Ultimately, the key to economy would start with your right foot, how desperate your driving habits are. When you see a red light ahead do you race up to it and wear your brakes down? Do you ease off the accelerator and coast up to the light? It's all relevant.

I find a good wax job also helps.

Falco.

[TieMyShoe]

36 hwy??? I commute hwy and I'm lucky to hit 18....

[punkrawker]

ya no kidding....are you travelling down a steep hill in neutral there falco?? and you have the 4d56 engine between the seats?? gotta say, i'm defiantly all ears on this one!!

[FalcoColumbarius]

I just worked it out and corrected my error. It's not 36 MPG (Imp.) Highway, like I originally posted (and corrected), which was off the top of my head. It's 34 MPG (Imp.) Highway. Remember that this is the best scenario of flat straight highway driving at a constant velocity (105-110 KPH) without wind interference.

36 hwy??? I commute hwy and I'm lucky to hit 18....

Stopping and starting in traffic on a highway is not "highway driving" when it comes to fuel economy. Nor is driving at 60 KPH with the rest of the traffic, slowing down, speeding up, &c..

When these machines are tuned they perform well. If you tweak the IP too much, you use more fuel. If you twist the turbo boost up beyond nine PSI You collect less air. If you don't change the air filter element or use one that has paper too thick, you get less performance. If you use inferior fuel ~ she doesn't burn cleanly. If you use inferior engine oil, the engine works harder and energy that could be sent to the axle ends up turning into heat instead. For two oil changes I could not get my then usual oil and used Castrol and I lost a kilometre per litre. Then there's compression. How are the seals? How did the last guy drive the Delica? Is there a leak in either the intake or exhaust manifolds? It's a standard with marine diesel engines to perform an overhaul after so many hours, why not motor vehicle diesels? What about the tyres? Are you using stock size? What pressure are you running your tyres at? How are you driving your wagon?

By the way, one thing I omitted to mention is I use Howe's Diesel Tread as a fuel additive.

Falco.

[punkrawker]

holly h3ll, I get 350km +/- per tank and I don't take her too far because my turbo is shot and waste gate is seized open so I get a very funny feeling that my mpg is mostly due to those two things. I am shopping around for a new turbo and waste gate and glad I have been shopping around because I have found new turbos anywhere from 300-800 new.....depending on where they are made go figure. You DEFAINTLY nailed it on the head when you asked "how did the last guy drive the van".....some peoples children....

[Mimic4]

In the name of science I plan to test this theory! Maybe we are all missing out. I purchased all of Falcos recommended frequent maintenance parts, and plan to change the oil/air/fuel filter. New oil, with additives as prescribed. & 9 PSI boost. Driving 105-115km/h. That and most importantly, turbo rebuild to get rid of my oil leak and make sure everything in there is okay and functioning perfectly!

Ideally if I can achieve higher that 25mpg I'll know there is something good to be had here! That would be a 5mpg increase for me ( and even that is downhill with the engine off xD)

I'll keep everyone posted as to how it goes, and Falco, if you have any other variables or additives worth mentioning please do as I will try to replicate your results as best as possible!

YAY SCIENCE.

[konadog]

I sure don't the best fuel economy at over 100 km/h. Pushing the air out of the way takes a huge amount od energy and the faster you go, the more energy is required. My automatic bus has the best hwy. fuel economy when I top out at 100 - though that's tricky now the limit is 120...

[FalcoColumbarius]

Mine cruises well at 120 but the fuel cost is great. 105-110 is the magic zone, I'm sure the IP is dialed into that speed for long distance cruising, at least mine appears to be. It makes sense if you're in a constant cruise and not accelerating, the IP is going to send less fuel to the motor until it needs more.

By the way, one thing I forgot to mention that is very relevant to fuel economy ~ wheel alignment. Paramount.

Just fuelled up having been driving winding West Van roads and lot's of hills, some commuter negotiating highway driving. Fuel light came on at 507 kliks, fuel worked out to eight and a quarter kliks to the litre.

Falco.

[Mimic4]

Thanks for all the information Falco! I'm impatiently awaiting my shipment of goodies from Rising Sun Imports, the new Sakura air element + Turbo rebuild and Oil/Fuel filter will be exciting to see in the van! I also got all new vacuum lines to rule out leaks!

I just re-read your posts and noticed some excellent points, I have a high-top "Crystal Light" while you have the low-top. Despite it's 5" taller, you have to square it out and multiply that by the length, and then multiply that extra area by the exponential grown of air resistance, so it could entirely be a notable difference! Especially in an engine that makes 90hp and peak. My friend who was helping me also noted the "crush formed" exhaust was very restrictive and suggested replacing even the downtube-cat assembly.

Does anyone know if there are any pre-made kits or folks making these exhausts in 2.5? Or would I need a custom build.. if you did get yours custom might I ask by who and for how much? :) Thanks!!

Falco, how many KM are on you odometer?

I can't wait to get everything together and start testing.. I do have a pretty soft foot ( I think ), and I try to minimize all of my brake usage, as if its a mini-game. Coasting to reds etc, I won't go on xP

Anyways thanks again for all the good tips and tricks and if others want to pitch in about their ideas on fuel savings techniques or just post their mileage i'd be very interested to see!

[TieMyShoe]

Stopping and starting in traffic on a highway is not "highway driving" when it comes to fuel economy. Nor is driving at 60 KPH with the rest of the traffic, slowing down, speeding up, &c..

I live 3 blocks off the freeway with 1 traffic light... commute between Abbotsford and Langley where I work 3 blocks off the freeway with two traffic lights... which I do 5 days a week... my commute is as hwy as it gets.

Here are Delilah's specs...
Rebuilt 4D56
-new head
-water pump
-timing belt
-belts and tensioners
-bearings (mains and con)
-new rings
-sonic cleaned and balanced pistons/con rods
-exhaust port polish
-all new gaskets and seals
-ip set stock
-egr delete
-15w40 Delvac Cj4

Rebuilt TD04
-all new internals including wheels and shaft
-set at gate pressure 10psi

Trans
-auto, new torq converter
-running synthetic red line atf

Differential
-rear LSD
-red high impact synthetic

Exhaust and dp
-2.5 mandrel bent exhuast
-magnaflow muffler

Tires
-215/65/15 all terrain
-49psi

Suspension
-2" lift
-alignment - yes

Other bits
-full safari rack
-4 roof mounted floods
-aftermarket roo bar w/ 2 8" floods
-rear ladder
-ns4 bike rack

My mileage has changed very little since I purchased it and since I have done the above listed work.

It's not that I don;t believe you.. it's more that I'm jealous you are able to get that kind of mileage. According to my motolog over the past 2 years my average econ is 24mpg. I am one of 4 in my group of friends with delis, we all get roughly the same mileage with the similar set up (high roof, ladder, rack, lighting, bike rack, lift kit) Mine just makes more power being a fresher engine. (slowest drag race ever.....)

I wonder if I should switch to a lighter weight oil.

[FalcoColumbarius]

I live 3 blocks off the freeway with 1 traffic light... commute between Abbotsford and Langley where I work 3 blocks off the freeway with two traffic lights... which I do 5 days a week... my commute is as hwy as it gets. .... .... It's not that I don;t believe you.. it's more that I'm jealous you are able to get that kind of mileage. According to my motolog over the past 2 years my average econ is 24mpg. ...

I concur, that's definitely highway driving. I had this image of Willingdon area.

First thing, just to clear the air ~ When I say MPG (Imp.), I mean Imperial gallons (4.55 litres), not American gallons (3.78 litres). Also, I'm not talking about highway with a basket on the roof, that would create drag, ergo more fuel. When I drive with roof bars and ladders on the roof, I don't get as good economy. The roof bars only go on when I have to deliver ladders to a site. Once they are at the site (or back home) the bars come off.

Another thing that we should consider in this thread is the fact that the quality of fuel has changed. In 2008 we were still running on LSD (500 PPM sulphur content). Now we're running on ULSD (15 PPM sulphur content). That has to be significant. In "Diesel Moot" there's this guy who works at the airport and runs his wagon on Jet A, which he says is 1,000 PPM sulphur content. I'd be curious as to his fuel economy.

Falco.

[Firesong]

Lol prairies with no wind... Like that EVER happens. My old L300 got its best fuel mileage in the city. But it was a std transmission with lower gearing. Amazing in the winter. The L400 can guzzle fuel like crazy in comparison.