Newbies and Vets: Tips for better fuel economy!

Best Mileage shift points questions.

First, some background. I have an '03 Jetta with 200K miles. If I drive easily, but hardly hypermiling, I get 50-55 MPG. If I drive on the thruway a lot at higher speeds, I get around 45MPG (speed kills your mileage even on the highway). Best mileage comes on back country roads avoiding stop signs and keeping the speed around 35-40MPH....there I can consistently get 70-80+MPG.

I'm looking for someone with graphs that show the interaction of RPMs and mileage. Yes I know about shifting at the torque inflection point, but I'm not interested in best 0-60, rather best MPG. What's the best shift points for this? Best MPG is attained in 5th gear at low RPMs, yes, but is it best to loaf up to speed, say shifting at 1800 RPMs in each gear, or hustle up there, shifting at 3500, and getting there quicker?
THIS OUGHT TO BE IN A GUIDE THAT'S A STICKIE. THIS IS WHY WE HAVE DIESELS (mostly). And yes, I know about all the other things for better MPG...I'm interested here in the shift points for max MPG

You'll get a lot of different answers to this question - how to accelerate, when to shift?

Most will say rapid acceleration results in better MPG. Despite technical evidence provided, mainly around BSFC charts, in practice, I have found (though testing far from statistically exacting) mild acceleration, with shifts around 2,000 rpm, get best MPG.

Certainly not 3,500. I'd say 2,200 max.

puntmeister said:

You'll get a lot of different answers to this question - how to accelerate, when to shift?

Most will say rapid acceleration results in better MPG. Despite technical evidence provided, mainly around BSFC charts, in practice, I have found (though testing far from statistically exacting) mild acceleration, with shifts around 2,000 rpm, get best MPG.

Certainly not 3,500. I'd say 2,200 max.

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The best MPG is not to have to accelerate at all, steady speed, aka highway at moderate speed. If you are doing constant stop and go... forget MPG. The best thing you can do is avoid heavy traffic, combine trips and not drive at all... the ultimate fuel saver.

I do kind of agree with you. My DSG is shifting at 2000-2200 RPM. My work commute is about 11.5 miles, only 5-6 miles is freeway. I find some times when I drive more spirited, accelerate smartly off stop lights, drive faster on the freeway for this commute, I see as good or even better MPH (per trip computer). I must admit feeling that torque off stop light or coming out of a sweeping turn, accelerating is fun, fuel burn be dammed. Sometimes you have to have fun.

The better MPG when I drive harder on my commute could be just how I catch the dozen possible lights, or getting there faster means turning the engine off sooner. However acceleration is energy and fuel, not withstanding the best BSFC at a given RPM/Torque (HP). Driving faster over the some crossover speed, where drag starts to dominate, thus more energy needed and more fuel. It is physics.

Here is a cool article
http://www.cbc.ca/news/canada/north/hyper-milers-maximize-fuel-efficiency-in-yukon-1.2695495

To me MPG is all about torque curves and RPMs. I work with truck drivers alot and the large diesels are the same. It is all about RPMs and torque curves. You can Google images for a torque curve on your vehicle and someone is bound to have put the same vehicle on a dyno at some point. For my 2003 peak torque is 1900-1950 RPM. After that it begins to drop off. Once you go beyond your peak torque you begin consuming more fuel. I will typically not go beyond 2250 RPM when shifting unless it is a very steep hill or something. You actually accelerate faster by shifting at lower RPMs in order to get into top gear as soon as you can for the conditions. This is called progressive shifting.
I also hear people say to coast as much as possible. This is very unsafe. I keep mine in the appropriate gear at all times and only go into neutral when I get below 20 MPH. If anything, my MPG has actually improved over the coasting driving style. The engine will provide braking horsepower by keeping it in gear down a hill or coming to a red light resulting in less use of the brakes and great engine efficiency. Turning your AC on while slowing down using this method also results in greater braking horsepower. I consistently get 52+ MPG this way.

I see people talking about putting their auto car in neutral to save fuel. I thought our cars used DFCO (Deceleration Fuel Cut Off), so wouldn't that defeat the purpose of putting it out of gear? The torque app on my phone says in gear slowing down its using 0 fuel.

millere5815 said:

I see people talking about putting their auto car in neutral to save fuel. I thought our cars used DFCO (Deceleration Fuel Cut Off), so wouldn't that defeat the purpose of putting it out of gear? The torque app on my phone says in gear slowing down its using 0 fuel.

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Your answer comes down to how far can you coast at speed in N compared to coasting in gear in over run. If you can coast farther in N compared to staying in gear, N saves fuel,

If the grade is steep enough or the distance is shortened to the point to not matter in how far you can or need to travel, then staying in gear is the better option......

Overrun produces drag shortening the possible distance traveled, that is what this comes down to. In Europe the DSG is programmed to automatically shift into N when you let up on the throttle in overrun, then seamlessly back into gear when the throttle is reapplied....

Somewhere in this string there is a VW/Audi produced chart showing the savings and when they are most from this automatically programmed option in their DSGs, not sold here............

At one time, in the early to mid 80s many automatics here had a shift selection option with this option, and it did increase mpgs!

Audi, Volvo and VW with diesels with automatics sold here from the early 1980s had a E selection on the shiftier. In E-mode when you pushed on the throttle the trans seamlessly shifted into gear. But when you let up on the throttle the car would go into N, allowing overrun.

I owned versions of all three with this transmission. Staying in D compared to using E in mixed urban/city driving made as much a 14 mpg difference! On the VW Passat 4cyl TD, the Audi 5000, and in the Volvo 5 cyl TDs 740, in all of these 25-27 in D compared to 38-41 mpgs when E was used...

I apologize in advance if this is posted in the wrong area....
I recently had Rich at Fix Em Haus install a .681 fifth gear in my 02 Jetta TDI (manual transmission). The first experience I had to use it only on the freeway was a few days ago. With no city driving the car achieved 65.5 mpg (at 2000-2100 rpm). I was amazed since I consistently average 53 mpg with city/hiway driving. I do not top off the tank because i'm trying to compare apples to apples.... so I was wondering 1) if 65 mpg is "real" and 2) about the consistency of fuel station pumps (whether different fuel pumps stop automatically at different levels). I welcome your comments and advice. Thanks!

it's about whether you are filling to the same level each time. each time being full that is. do a ventectomy, fill up till you see fuel at the edge. do the same thing next time.
although it says on the pump "Do Not Top Off", it's referring to gas, not diesel.
i wouldn't trust the 65.5 until you run through a full tank and then another. average means just that: not just for one leg of the journey, the WHOLE journey.

Thanks. I'll start that right off.
I average 53 mpg... and did both before and after install of the .681 fifth gear.
I'll be on a long drive back east in a few weeks and will have a good opportunity to test the hiway mpg.

On my '97 Passat TDI I went with larger diameter tires and saw over 2% increase in mpg even after correcting for odo error. I did not worry about tire weight because I didn't know I should worry. I think the older cars really need higher gearing. Now with my 2013 Passat I will stick with stock size tires because the gearing is already very high.

My new Passat gives appreciably better mpg than the old one, but the old one might have done better if it didn't have 90k on it when I bought it (who knows how well it was taken care of), and wasn't running most of the time with a plugged intake...

I'm still of the mind that coasting in gear is better than going to N / declutching. If you aren't using your momentum to spin the motor, then you are burning fuel to run alternator, AC, PS pump, etc, etc. Yes you might have to give the motor a bit of throttle if you are going down a steep hill, but usually when I supplement my coasting with a bit of throttle to maintain speed, I'm still seeing 100+ mpg.

Plus, even if I'm wrong, going in and out of gear is going to cause additional wear on trans/clutch. It really comes down to personal preference. I'm happy staying in gear.

Although, if VW tested this and found disengaging gear was better, why didn't they bring it to US? Probably our heavy infestation of sue-happy lawyers!

Are we all confirmed there is a mpg improvement between cold and running temp.
If so,
how do you accelerate the rise to running temp during freezing winters?
-Block/part block the radiator with a shield?
-special remap/chip for cold weather?
-does the car adjust automatically?
-special engine coolant?

any comments?

Those in REALLY cold places (Canada and parts of US where sub-freezing temps are common) often get a bra/cover to limit air intake and/or get engine block heaters (I think the Canadian ones come with engine block heaters as standard issue). Also, some recommend not turning on the cabin heat until the engine is warmed up, but I suspect that's too minor to really matter. Don't start the car and let it idle to warm up--it won't warm much without load on the engine and you blow any mileage improvement from a warmer engine by the fuel lost idling (and it's bad for the environment). I'm in a relatively mild area, but my big move to aid in warm-up is that I finally cleared out enough of the garage to park a car in it. The garage is unheated, but still an easy 20F warmer than outside in the winter.

good tips thanks.i will try those.no garage so i will park behind a wall.

Any kind of cover would be a second to a garage - anything to block it from radiating heat to the night sky

TDI Milage

I hear a lot of things about increasing TDI milage but the best thing to do is to change your oil, with the recomended oil from Volkswagen every 5k instead of 10k as recomended. I just drove from Alabama to NY and back and averaged 46.5 mpg and I drove thru VA and WV. I am going to change my timing belt this week. I have all the tools.

evoblade said:

Although, if VW tested this and found disengaging gear was better, why didn't they bring it to US? Probably our heavy infestation of sue-happy lawyers!

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I'm not 100% certain, but here is my theory: In the U.S., it is typically illegal to coast in neutral.

Although this law is probably intended to apply to manuals, the law probably doesn't specify.

As such, auto manufacturers are either legally required to sell auto-equipped cars which coast in gear, or face litigation every-time one gets into an accident.

geomikehat said:

I hear a lot of things about increasing TDI milage but the best thing to do is to change your oil

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what oil you putting in?
how much? is just above minimum best for fuel efficiency?

I'm somewhat dubious that shortened oil-change-intervals would lead to meaningfully better MPG.

geomikehat said:

I hear a lot of things about increasing TDI milage but the best thing to do is to change your oil, with the recomended oil from Volkswagen every 5k instead of 10k as recomended. I just drove from Alabama to NY and back and averaged 46.5 mpg and I drove thru VA and WV. I am going to change my timing belt this week. I have all the tools.

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This is the first time I have heard of changing your oil twice as often in an attempt to increase fuel mileage.

Can you quote a source for this revelation?

Thanks,

Bill

First time I've heard it too - stick to the owners manual, anything less than 10k intervals will do more harm and wear than good. I like Lincoln's comment above so much I'm going to add it to the list and do a much needed update to the first post tonight, hopefully you're ok with that
Cheers!
-BB

BleachedBora said:

First time I've heard it too - stick to the owners manual, anything less than 10k intervals will do more harm and wear than good.
-BB

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How would putting in new oil before the interval harm the engine?

oil change? NO!
slow down? YES!
proper tires/inflation? YES!
proper gauge to monitor current conditions? YES!
tighten the loose nut behind the wheel? YES.
i consistantly get 60 mpg and there are NO magic tricks that i use to get it. i drive sensible.

deejaaa said:

oil change? NO!
slow down? YES!
proper tires/inflation? YES!
proper gauge to monitor current conditions? YES!
tighten the loose nut behind the wheel? YES.
i consistantly get 60 mpg and there are NO magic tricks that i use to get it. i drive sensible.

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How much pressure you running in the tires & how fast are you going on the highway getting 60 mpg?

i am doing as many as these as i can. i have the same user name on this forum.
http://ecomodder.com/forum/EM-hypermiling-driving-tips-ecodriving.php
50 psi, 60 mph.

I bought my 2nd identical 04 PD TDI and was so upset to find that it consistently got about 4mpg less than my first one. I checked EVERYTHING: fuel pump, temp sensor, tires, alignment, dragging brakes, turbo leaks... used Pulse/Glide and STILL only managed to get 38-39mpg. Called the dealership, had them check my programing and they said it was normal for cars to be 4-6 mpg off from each other. (morons) I was so mad! Then I read a wonderful article regarding TORSION VALUE. Turns out that Jettas like about +1 degree advance. Mine was set to a default 0.0. I went in and changed it to 1 and VIOLA! My mpg's shot back up to 41-43 range This requires a VAG COM tool and a couple wrenches, but is super easy to do. So glad it wasn't cam wear or something.

PS I believe the amount of money wasted on changing oil every 5k instead of 10k would be more expensive than the amount of money you would save over that duration in MPG increase (if any at all). I go 10k and have no problems. The oils we are forced to use are so good, that 10k is not a problem for them. Just periodically make sure your level is ok.

deejaaa said:

i am doing as many as these as i can. i have the same user name on this forum.
http://ecomodder.com/forum/EM-hypermiling-driving-tips-ecodriving.php
50 psi, 60 mph.

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Good heavens, that's way over the maximum pressure limit stamped on the dial of my current set of tires.

I don't doubt that these tires are part of the reason I can no longer break 40 mpg, torsion value might be another, but I can't find anyone willing to adjust it around here - no gurus, only dealers.

Now I'm beginning to wonder how much mileage I could be losing due to a faulty thermostat... Now that the weather's turned cooler I'm not getting up to operating temperature anymore, AND I have a coolant leak from that general area.

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what do you guys think of disabling the daytime running lights to conserve fuel? obviously the safety factor of having them on is higher, but will it gain me any fuel?

thanks.

Anytime electrical consumption is reduced, fuel consumption is reduced, since all of the electricity is derived from the diesel-motor.

Just the same, I think the savings from disabling daytime running lights would be negligible.

Everything is a cost/benefit.

You could also save fuel by removing the excess weight of the passenger seats. If you have kids and/or a spouse they could just sit on the floor. Better yet, they could walk.

Nlens said:

what do you guys think of disabling the daytime running lights to conserve fuel? obviously the safety factor of having them on is higher, but will it gain me any fuel?

thanks.

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The short answer is NO, it will not save you a measurable amount of fuel. If you search, you may find that this was discussed about 6 or so years ago.

Bill