Tuning for best MPG

[92EcoDiesel Jetta]

I've got the timing set at 1.0". What are some of the things you've tried (other than a light foot) to get better mpg? Timing adjustment?  Fuel screw adjustment? injector nozzles? Pleas provide details.

[DieselBalz]

Taller tires (not wider), transmission with taller gears, crank the fuel screw out. That's taken me from 28 mpg to 33 mpg.

[R.O.R-2.0]

Taller tires (not wider), transmission with taller gears, crank the fuel screw out. That's taken me from 28 mpg to 33 mpg.

do you have a cat still?

[nathan_b]

Taller tires (not wider), transmission with taller gears, crank the fuel screw out. That's taken me from 28 mpg to 33 mpg.

hope thats in a vanagon, belching smoke, I cant get my caddy below 35mpg.

Step 1: make sure all maintenance is up to date.

then start making tweaks,... timing, ect and measure the results. if bad, go back. just keep building on your tuning.

13" light wheels and tall tires are great for mpg as well.

[wdkingery]

This is the only reason I got this car. Mpg.
I'm hitting 49's pretty consistently, with an average of 47 (and i started @ 40 or so mpg so that's holding me down some) and a high of 53.4 although my odometer can have a up to a 3% discrepancy (high)
Definitely pump the piss out of the tires. I run 40 psi on stock 175/70/13's
I turned the fuel screw back from its original setting, although I'm not sure that helped.
Hypermile.
Shift early. I originally hit 5th gear by 25 mph, but have since stretched that to 35ish. Work the torque.
Limit top speed. I often do 60 mph in a 70 zone, and try never to exceed 53 mph.
The best mpg additive so far has been P/S white bottle (its what I was running when I set my own record) i've tried 2 stroke, parrafin wax, stanadyne, and Lucas.

No muffler, no smoke, never floor it, slow down, advance timin to 042 or so.

Essentially its like driving a handicap school bus

[RabbitJockey]

i can't drive my cars for mileage... i just cant haha, but i can do all the other stuff to help, and i am curious what timing settings help mpg, they are kind of irrelevant to me since i have a yellow dot pump, but i can at least get an idea if advance helps or hurts.

[ORCoaster]

You want mileage?  You want performance?  Best choose now because one kind of exclusive of the other.  At least after a point. 
What have I done.  More than any man should but that is past history.

I don't set the timing to anything because I can't measure it anyway.  To cheap to get a gauge and adapter.  But I am close to you in the 49 zone most times.

I tried the water bubbler route putting water in the mix that goes back to the engine.  Quieter but no mileage gain, maybe even lost some because i was filtering out all the oil that would have been burned otherwise.

I have 550 by 170 by 13 inch tires on pumped up to 40 PSI.  When I ran the wider tires it rode smoother but these roll on like crazy
 
I have played with the IP internal pressure hoping to get more advance out of it at my cruising speed, 65.  You are driving that thing like an old lady.  I have heard to run up the RPMs before shifting not to lug it.  5th at 25?  I get to number 5 at 65 and then sit back for the ride.

I had the injectors rebuilt and am running the 135's
 
I draft large trucks and RVs or diesels pulling travel trailers and let them move that wall of wind out of the way for me.  I don't tailgate but you can feel when you are in the zone of less resistance.

I put an air dam on the front end.  Very stylish, that forced the rest of a Zender body kit to be added to make it look right.

I change oil at 3000 miles and the filter as well.  OK so I am not that cheap.

I run 2 oz of paraffin wax and 3 oz of ATF in my ten gallons of fuel.
 
I over-sized the weenie snorkel to a three inch heater vent duct.  The metal kind that can be squeezed into an oval at the air cleaner.  Oh and i keep the air cleaner clean by blowing compressed air backwards through it.

I painted it and it is both shiny and smooth as glass.   I also made sure the sunroof was adjusted to the roof line and the doors were not hanging out catching the wind.

When I timed it this last time I didn't have the pressure at idle to the 43 lbs area.  In fact it was 10 psi, smoke rolling out the back at full retard and rough idle.  Bumped up the timing a smidgen and the smoke quit right away.  Then I tapped the regulator screw in until I registered 37.5 lbs at idle.  Seems to have all the power I need in town.  I am tempted to back the fuel screw out the usual 1/16th of a turn but am going to make sure I have the power to climb these few hills along my route before I do that.  If I short the max fuel screw and run to lean I have to downshift, rev it up and don't feel that is necessary with the 5 speed.  I treat the trans like a three speed with two overdrives since that is how I read the gearing on my FF.

If I put a turbo on it I don't think I can lean it out with the IP I have so I think I am going to get off that track.  I wonder if I would do better driving like a short bus.  I just can't do that!  Time is money in itself so I burn the fuel to make the time.  But like I said cruise for me is not 55 anyway.  The car really mellows out at 67, no vibration and the sound changes some.

I think this is about all of it.  Some you have tried others you might. 

[DJPyro]

Um... My mk3 with an AAZ averages 38-43mpg in town, driving the bag out of it. I need to rebuild my injectors, and it's stock except a perforated air box, and a straight through 2.25" exhaust. Timing is at .95ish IIRC. I don't do anything special. However, my mileage doesn't really improve a reasonable amount if I baby-foot it either. *shrug* That's why I bought a diesel.

I expect I could get up to high 40s if I refreshed my fuel system, and took care of a few niggling problems, but I didn't buy it to hypermile, I bought it to get the best mileage I could while having as much fun in it as possible. 40mpg average is more than adequate for me to feel that way about my far.

[DieselBalz]

Taller tires (not wider), transmission with taller gears, crank the fuel screw out. That's taken me from 28 mpg to 33 mpg.

do you have a cat still?

No sir. From the dp there is straight pipe to a resonator. And than maybe five inches more pipe before it dumps out just in front of the left rear tire.

[92EcoDiesel Jetta]

From a 10 mm 6 point socket, I left 2 flats alone and grounded the other flats round to fit the pressure regulator bolt. It worked well to take out the regulator bolt from a practice IP that I have. I'm thinking, instead of using a hammer and a drift to tap the plunger in the bolt to up the pressure, use a c-clamp and a pin to push the plunger in little by little. This way you have a lot more control. I would measure the depth of the plunger with a vernier caliper to keep track of how far it was pushed.

As I recall, that was no alum or copper washer on that regulator bolt, just 2 o-rings. Can you confirm?

You want mileage?  You want performance?  Best choose now because one kind of exclusive of the other.  At least after a point. 
What have I done.  More than any man should but that is past history.

I don't set the timing to anything because I can't measure it anyway.  To cheap to get a gauge and adapter.  But I am close to you in the 49 zone most times.

I tried the water bubbler route putting water in the mix that goes back to the engine.  Quieter but no mileage gain, maybe even lost some because i was filtering out all the oil that would have been burned otherwise.

I have 550 by 170 by 13 inch tires on pumped up to 40 PSI.  When I ran the wider tires it rode smoother but these roll on like crazy
 
I have played with the IP internal pressure hoping to get more advance out of it at my cruising speed, 65.  You are driving that thing like an old lady.  I have heard to run up the RPMs before shifting not to lug it.  5th at 25?  I get to number 5 at 65 and then sit back for the ride.

I had the injectors rebuilt and am running the 135's
 
I draft large trucks and RVs or diesels pulling travel trailers and let them move that wall of wind out of the way for me.  I don't tailgate but you can feel when you are in the zone of less resistance.

I put an air dam on the front end.  Very stylish, that forced the rest of a Zender body kit to be added to make it look right.

I change oil at 3000 miles and the filter as well.  OK so I am not that cheap.

I run 2 oz of paraffin wax and 3 oz of ATF in my ten gallons of fuel.
 
I over-sized the weenie snorkel to a three inch heater vent duct.  The metal kind that can be squeezed into an oval at the air cleaner.  Oh and i keep the air cleaner clean by blowing compressed air backwards through it.

I painted it and it is both shiny and smooth as glass.   I also made sure the sunroof was adjusted to the roof line and the doors were not hanging out catching the wind.

When I timed it this last time I didn't have the pressure at idle to the 43 lbs area.  In fact it was 10 psi, smoke rolling out the back at full retard and rough idle.  Bumped up the timing a smidgen and the smoke quit right away.  Then I tapped the regulator screw in until I registered 37.5 lbs at idle.  Seems to have all the power I need in town.  I am tempted to back the fuel screw out the usual 1/16th of a turn but am going to make sure I have the power to climb these few hills along my route before I do that.  If I short the max fuel screw and run to lean I have to downshift, rev it up and don't feel that is necessary with the 5 speed.  I treat the trans like a three speed with two overdrives since that is how I read the gearing on my FF.

If I put a turbo on it I don't think I can lean it out with the IP I have so I think I am going to get off that track.  I wonder if I would do better driving like a short bus.  I just can't do that!  Time is money in itself so I burn the fuel to make the time.  But like I said cruise for me is not 55 anyway.  The car really mellows out at 67, no vibration and the sound changes some.

I think this is about all of it.  Some you have tried others you might. 

[mtrans]

As I recall, that was no alum or copper washer on that regulator bolt, just 2 o-rings. Can you confirm?

Yes.

[92EcoDiesel Jetta]

I still have the stock Cat. How much of a mpg improvement can I expect if I cut it out and splice a pipe in its place? How much of a noise increase?

[xxkoadyxx]

i can't drive my cars for mileage... i just cant haha, but i can do all the other stuff to help, and i am curious what timing settings help mpg, they are kind of irrelevant to me since i have a yellow dot pump, but i can at least get an idea if advance helps or hurts.

same here bud, but i still get a decent 500 MIN kms to a tank.. idk if thats good or not..

[vanbcguy]

My last run down to Portland got me about 750KM before I refilled, put in about 49L in to a 55L tank on Jezzie... 6.5L/100KM was the actual number I computed at the time.  That's the best run I've had in the car yet.  Driving about 10 over the limit the whole way, WOT on the onramps...

I noticed a definite mileage improvement after I added my intercooler.  I don't really have a great plot of mileage for my car since I end up with a trailer on the back of her fairly often, but I'd put it at as much as 15% better.

[92EcoDiesel Jetta]

i can't drive my cars for mileage... i just cant haha, but i can do all the other stuff to help, and i am curious what timing settings help mpg, they are kind of irrelevant to me since i have a yellow dot pump, but i can at least get an idea if advance helps or hurts.

same here bud, but i still get a decent 500 MIN kms to a tank.. idk if thats good or not..

How big is your tank? I think I've gotten 600 miles per tank and my tank is 13.9 gal.