Newbies and Vets: Tips for better fuel economy!

[jmw10]

Why do I get better MPG driving country roads than. Highway
Your average speed is lower. High speeds decrease my mileage as well.

 

[rotarykid]

Why do I get better MPG driving country roads than. Highway
Your average speed is lower. High speeds decrease my mileage as well.

On every car or truck I've ever owned I always get the highest mpgs on mixed city , lower speed rural & urban routes because of lower average speeds .

My maximum mpgs are running southeastern NC islands where my speeds rarely if ever exceeded 45 mph in "N" & top gear mostly . With a couple of max mpgs hit running around the Denver metro area .

Running around Lake Tahoe CA/NV a couple of weeks back I hit close to 35 mpgs @ 30-60 mph in an automatic 05 Accord . On the roads around the lake as anyone that has driven on these roads can tell you are lucky to get much above 35-40 mph for more than 100 yards at a time . Granted I used a lot of "N" where no extra speed was required and lower gears to avoid brake use on the steep grades .

On the highway I'm lucky with a lot of effort to break 29- 32.5 mpgUS on the thing .

 

[Jnitrofish]

A lot of people seem to confuse city driving with slow driving, when the effects on your MPG are totally different between the two.

The reason city MPG is low is because you have stop and go; you are accelerating using a lot of fuel, and most of the time (unless you are an expert at timing lights) you are hitting the brakes wasting that kinetic energy you used the fuel to build, and then the cycle repeats. The result is low MPG.

Slow (constant/rural road driving) is optimal, since you can cruise for a long time in a high gear (low RPM) without much throttle at all due to the lower amount of wind resistance (aerodynamic drag) from trying to slice through the air at a lower speed. Result is great MPG.

Highway driving is the median MPG; you can cruise at a constant speed in the highest gear, but you are traveling faster so there is more aerodynamic drag, reducing your fuel mileage.

Remember, we can breathe because there are gasses there (air), and those gasses have mass, and everything that moves through this soup of gasses must expend energy to do so.

Why do I get better MPG driving country roads than. Highway

 

[NarfBLAST]

Jnitrofish, Great explanation... but I think you meant to say "at lower rpm" instead of "lower gear" a couple of times there?

 

[Jnitrofish]

Jnitrofish, Great explanation... but I think you meant to say "at lower rpm" instead of "lower gear" a couple of times there?

Yeah that's something I regularly mix up. Edited. Thanks.

 

[Turbospool]

Yeah that's something I regularly mix up. Edited. Thanks.

Yup ... edited explanation is spot on folks.... a scanguage helps to verify what he just said. The proof is in several successive fillups.

 

[Tom Servo]

Slow (constant/rural road driving) is optimal, since you can cruise for a long time in a high gear (low RPM) without much throttle at all due to the lower amount of wind resistance (aerodynamic drag) from trying to slice through the air at a lower speed. Result is great MPG.

I got a prime example of how true this is, many years ago on a trip to Panama City from Birmingham. A friend and I left out at about 3 am to stay out of the traffic and sun. We drove all night along a route that was 40% interstate, 60% US highways.

South of Montgomery, we hit dense fog and had to slow down. We did about 190 miles at 40-45 mph. Despite the tank being mostly urban highway commuting, the fillup gave me my highest mileage ever at just over 54 mpg. We repeated the route for the return trip and I went back to my normal urban commute thereafter. The next tank was down around 47 mpg. I attributed it to the fact we were able to do 55-75 mph the whole way back.

Slow and steady definitely wins the race. In a few days I'll be relocating to the Gulf Coast and will be surrounded by miles of rural two lane roads on relatively flat ground. I bet my mileage will increase because I'll be off the interstates completely.

 

[BleachedBora]

Nitro,
I really like the way you put that; if you don't mind I'd like to incorporate part of that into my first post? Take a look...

Thanks!
-BB

 

[Jnitrofish]

Love it BB! Thanks.

 

[3516ACERT]

I've only got 18k miles on my '10 wagon so far, so I cannot be a reasonable voice of experience - but I have almost a million miles behind the wheel of a 3406 Cat engine in my previous profession if that gives me any credibility.

The factor that reduces the average mpg most significantly is either the brake or the down-shift. Every time you touch the brakes, necessary or not, you're wasting fuel. I am pretty sure down-shifting costs more fuel than braking, especially if you brake in neutral.

I noticed in my daily commute, the computer gives me 50mpg on the way to work, but only 40mpg on the way home.

Topography was the answer - my home is 600' above sea level, the office is at 350' so don't underestimate the value of neutral driving downhill. (ENGINE RUNNING)

I DO NOT recommend turning the engine off while driving. Not only is your power steering useless, but after one pump of the brake you and your emergency brake are on your own. It is definitely not worth the collision deductible to save a little fuel when somebody gets between you and 60 mpg. I don't even want to think about someone forgetting to turn the key back to the right position and having the steering wheel lock. (I read the first 5 pages before skipping to the end, sorry if that's been discussed to death)

I can understand spending the money to max out mpg with bigger turbos and removing power robbing auxiliary equipment, but besides the strong desire to be more green, it costs a lot of miles at 55mpg to pay back the improvements made at 50mpg.

I paid about $2k extra for the diesel vs. the gas engine on my wagon. That means I need to drive about 60,000 miles to pay off that premium price for better mileage. Since I know this engine will run for about a half million miles, I figure it's worth it... stay tuned.

 

[jasonm11]

In a manual trans car you pay more attention not less when cruising with then engine off which equals safer . If I see I'm going to need more acceleration I can have it running in about the same time it takes someone to get back on the throttle in a running car .

When you see you are going to have to stop or need extra acceleration just use your momentum in the highest gear possible to re crank the engine just as it is required saving battery power & starter life .

If this is done properly no more strain is put on the drive train than shifting gears up or down or accelerating & decelerating in gear . Just let the clutch out just enough to get the engine going no more then get into the required gear drive off .

In an automatic it does take more electricity which equals more fuel used less fuel saved to do this but there is a payoff if done with care . Plus the extra strain put on the starter .

Actually, shutting down the engine and restarting by using driveline power is hard on the engine components. i have done it myself but it is much more of a strain on engine bearings than using the starter to fire it up.

 

[dieseltwitch]

Actually, shutting down the engine and restarting by using driveline power is hard on the engine components. i have done it myself but it is much more of a strain on engine bearings than using the starter to fire it up.

How?
being that the torque for starting a motor either with the clutch or using the starter enters in the same location, it might even be said that using the clutch might be easier on a motors mains due to that fact that the torque from clutch is centered around the same axis as the crank and evenly spread. Using the starter puts the applied torque on only one point on the fly wheel ring gear. and the ring gear is a straight gear not a helical gear so they are trying to push each other apart. I'm not saying either one is better then the other I just don't understand how using the clutch and drive train to start the motor is any harder then using the starter.

 

[jpv]

Say WHAT?

Make up something else.


Do not use a KandN filter on a TDI, but the fact that the TDI has a turbo has absolutely nothing to do with why you should not use one on a TDI.

Bill

Its not made up its a fact and I'm relaying the info to help someone. Regular filters are made of filter materal (paper). KNN filters work on the principle of a thick liquid (oil) whick traps and holds the dust and dirt. A turbo charged engine created a lot of suction and pulls the oil out of the filter which is loaded with dust and dirt and it ends up in the engine and scratches the internal components ruining the engine. A normally asperated engine does not produce the suction that a turbo charged engine produces and as such a KNN filter is more sutable for that application.

 

[dieseltwitch]

That and Oiled filters like to screw up MAF sensors

 

[ruking]

Actually one of the reasons is the wide and huge range of what people want/need say they want/need but willing/unwilling to do. probably really importantly are actually doing. The forum really allows the room to let things be as they are or will be. There are many ways of approaching the issues (as you have noted). But let me just respond to your points.

On your basic question of fuel economy, 1. for $1k are you envisioning a B/E or 2. just want better mpg for general principles? 3. What mpg or 4. increase do you envision? Your sentence ..."I am a conservative driver so I understand that there are significant gains to fuel economy just by lessening the pressure on the gas pedal "... leads me to believe you ought to start with the (YOUR) VW owners manual technical page and understand and be able to execute what those figures really mean. You also might go through 2 break in threads

http://forums.tdiclub.com/showthread.php?t=252501

http://forums.tdiclub.com/showthread.php?t=48940

The real issue is longer term the TDI and DPF benefits from slightly to more aggressive operation. This might be a tad to wildly counterintuitive to someone seeing themselves as "conservative", higher mpg driven.

Your items # 1 and #6 are really the best starting point. Why do you want hidden GREATER hp/torque when you state you will use it little to none of the time? Why do you want new nozzles (item #6) for only better fuel mileage when you have a min of 150,000-200,000 miles to go on your BRAND new OE nozzles? Keep in mind there was a 55%/52 % hp/torque BOOST in the Mark IV generation TDI. My signature reflects the mpg premium somewhat.

Item #2 STAY with oem air filters !!! Leave it in for 80,000 to 100,000 miles (yes I know the VW recommendation is @ 40,000 miles)

Item #3 leave your exhaust ALONE !!

Item #4 get your tire pressure up to 85% of max side wall pressure. So if you have 51 psi tire 44 to 42 psi. If you have a 44 psi tire 38-36 psi.

Item #5 is a bit harder to measure. Sure tint to lower temp is measurable etc. But when you set the A/C ON with fan on speed 1 (higher speeds put higher demand, aka lower mpg) that will give you a measurable difference. I would also select a white Jetta in line with this theme.

 

[ruking]

Thanks ruking! I appreciate the honesty and help.

1. I will pay better attention to the break-in recommendation via the threads and the owners manual. I should have defined what I meant by conservative. I don't go 90 mph down the highway...everyone in Texas does, just the way people drive. My life isn't worth getting to work 3 minutes earlier, which is why I stick in the 60-73 mph range.

2. I am not really looking to B/E, it is more the principle of fuel economy. I have frequent long cummutes. My daily commute is 45 miles each way, and I often travel home which is 700 miles. I am hoping to be part of the 700 mile or even 800 mile club someday. Getting home on one tank of gas would be rather funny to me considering how things use to be

3. I am seeing MPG around 46 on full tank. Which is great. Better than EPA estimates of course which aren't even close. I am more than pleased. I am just hoping to get to 50 mpg * 14.5 Gallon Tank = 700 mile club. (No, I will not run it down to zero just to achieve this.)

OK to #'s 1

Item # 2. SWAG numbers indicate 23,760 miles per year (45 miles* 2 * 22 per mo*12 mo=) Basically if you CONSISTENTLY get 50+ mpg you will save 42 gals per year/12, 3.5 gals per mo. @3.30 per gal that is 139 per year or 11.55 per mo.

Item #3 probably puts you in the (that guy is probably BS'ing) category. To me, 46 is infinitely achieveable. I get a range of 40-47 (per signature) and I don't even try and we post on the monthly mpg competition with 3 drivers !? On the road, when we keep it under 92 mpg, posting 44 to 42 is the norm. There is no doubt that 50+ is achieveable. I/we are not wanting to do what it takes to GET 50 mpg+. Conversely, this is easily achieveable in the Mark IV.

The short hand is easy once you know. Max efficiency and torque is delivered between 1,750 to 2,500 rpm. If you want better mpg, move your rig closer to 1,750 rpm. If you don't mind a slight fall off in mpg, but still in the max efficiency range.... 2,500 rpm. Confirm this in your VW oem owners manual technical page. (09 TDI is on p 361 or some such?) Also max hp is delivered @ 4,000 rpm So those percentages (of a 5,100 rpm redline) are between 34.3% to 49%. Max hp is @ 78.4%.

This is NOT in the owners manual but: The sweet spot range is between 1,750 to 3,500 rpm. Needless to say @ 2,900 rpm (6th gear)you are cooking along.

 

[ruking]

I am BS'ing? Huh....interesting assumption. Making the newbie feel welcomed

Defacto, that puts me in that category also. But there are a fair amount and % of folks who are disappointed @ the fuel mileage they do get.

 

[charliekripple]

Soot?

Hello, I`m a newbie to this site, but not to diesels. Sometime back I purchased a used 98 jetta TDI. It ran well, but I was getting 42mpg. I was dissapointed having just gotten rid of a P.O.S. 85 jetta TDI that was getting 50-56mpg, but was falling apart around the engine. I took my 98 to a friend and diesel mechanic who took the top off the engine clean up the valves and intake,(valve job), and reassemble everything back to spec. He told me that to cut emmissions,VW did a exhaust gas recirculation and it had sooted up the intake system. He closed off the exhaust and behold. The car ran the same, but started to give me 48-50mpg regardless of how I drove. Interstate driving at 65mph or better gave me 55mpg. My mechanic friend has told me he has had two more TDIs with the same problem.

I`m just startin to read past posts,but haven`t found one that had this prob as yet. I would like to hear any comments as I was wondering if the new jettas have EGR. Consumer reports have the new jetta tdi listed at 47 mpg hwy.

 

[charliekripple]

Geez, I just saw this same thing I described in the TDIFAQ. oh well.

 

[vwjettadsl]

For those that live in the Midwest, Casey's General Store gas stations have an average cetane level of 43-44.

 

[gsxr1k]

What's your guys take on the www.advancedautomotion.com Drop in 6 Speeds for the MKIV/MKV Save Thousands! thread? When I have to have the clutch changed thought of this upgrade.

 

[rotarykid]

Hello, I`m a newbie to this site, but not to diesels. Sometime back I purchased a used 98 jetta TDI. It ran well, but I was getting 42mpg. I was disappointed having just gotten rid of a P.O.S. 85 jetta TDI ( no such thing ) that was getting 50-56mpg, but was falling apart around the engine.

There were no TDIs before 1991 and that was only in Europe only in the an Audi . VW got their first TDI in 94 in Europe and we got our first TDI in North America in mid 96 in mostly the Passat . A few Jettas and Golfs were sold here in mid 96 but most of them started showing up in 97 & up . the New Beetle got the TDI from the start in 98 in North America .

If you had a 85 Jetta Diesel it was a mechanically injected IDI , indirect injection diesel . The TDIs are computer controlled direct injection , a completely different animal .

On a 98 Jetta TDI if the timing is set late you will see lower mpgs . Taller tires also will improve mpgs . A timing mod along with much taller tires ( 205-215 / 75 range ) can put that car well into the low to mid 50s mpgUS in everyday driving .

 

[rotarykid]

What's your guys take on the www.advancedautomotion.com Drop in 6 Speeds for the MKIV/MKV Save Thousands! thread? When I have to have the clutch changed thought of this upgrade.

A cheaper and better working idea is the one I've been using for over 30 years . Just install taller 75 series tires and inflate to 38-40 psig on any car of any type and you will see a rise in mpgs , I have 3,000,000+ miles of clocked data on all types of cars gas & diesel to back up that statement . This raises the gearing , makes all the gears taller not just the highest gear . If you use this gearing improvement properly you will a rise in mpgs .

 

[inlarry]

This is only really applicable if you live in Indiana, Illinois, Kentucky or Ohio, and likely limited availibility outside S. IN, IL and NW KY.

Countrymark fuels Diesel-R brand diesel fuel has a cetane rating of 50 according to their website. Some blends are a bio blend, though I've been able to receive any confirmation of the specific blend (so I assume <5). I know in Evansville, IN the only place I can *confirm* that sells Diesel-R is Superior Ag co-op just off of St. Joe. There are however countrymark branded stations throughout the area, but you'll need to verify with the station whether they're selling the -R brand, or simply the standard ULS blend (which I've been unable to get numbers on). They also offer Super Dieselex-4 which they label as an "off-road" fuel, which I'm not sure why. It's a 15ppm fuel with a 50+ minimum cetane rating, I can only assume it's a dyed fuel.

From what I can tell, the Diesel-R is the highest rated (cetane) fuel available in this area. Plus, Countrymark refines only American crude, mostly Illinois Basin Lt. Sweet Crude (which in general yields a higher quality fuel than other crude sources).

Again, to ensure you're receiving the 50 c-rating be sure you confirm it's the Diesel-R, not their standard #2 (which should still have a better rating than most other brands).

Countrymark fuels are available at most Huck's, EnergyPlus 24, Countrymark, and co-op branded stations. For a list of stations visit www.countrymarklocations.com

 

[BleachedBora]

I put that on the first post, thanks inlarry!

 

[gsxr1k]

A cheaper and better working idea is the one I've been using for over 30 years . Just install taller 75 series tires and inflate to 38-40 psig on any car of any type and you will see a rise in mpgs , I have 3,000,000+ miles of clocked data on all types of cars gas & diesel to back up that statement . This raises the gearing , makes all the gears taller not just the highest gear . If you use this gearing improvement properly you will a rise in mpgs .

Very true, that's cheaper. Thing is I don't prefer tall skinny tires. I like tight handling in corners, sporty looks, etc. That's just my preference.

 

[Tom Servo]

Very true, that's cheaper. Thing is I don't prefer tall skinny tires. I like tight handling in corners, sporty looks, etc. That's just my preference.

That's one of the (many) pleasant things about our TDIs. We still manage to get pretty good mileage while not compromising on handling and driveability. Part of what gets a Prius such great mileage is all the bits they shave off, like having narrow tires. I'd rather stick to the road more and lose a few MPGs.

 

[NarfBLAST]

I'd rather stick to the road more and lose a few MPGs.

Arguably you are not loosing any MPG depending on your driving habits. Might even gain some by driving a TDI vs a Prius.

 

[ruking]

That's one of the (many) pleasant things about our TDIs. We still manage to get pretty good mileage while not compromising on handling and driveability. Part of what gets a Prius such great mileage is all the bits they shave off, like having narrow tires. I'd rather stick to the road more and lose a few MPGs.

Two main things that auger in your favor. Probably first and foremost is the VW (TDI) is really designed for the autobahn. Prius while it can probably handle the autobahnn, is NOT. Second, the Prius/TDI is a apples to oranges, strawman comparison. When you consider the power specifications a more even one is the Camry Hybrid/ VW TDI comparison. In most every measure in that comparison, the VW TDI Jetta wins over the Camry/Hybrid. Lower priced, better mpg, better adaptation to the American system of roads.

 

[NewTdi]

Two main things that auger in your favor. Probably first and foremost is the VW (TDI) is really designed for the autobahn. Lower priced, better mpg, better adaptation to the American system of roads.

Even with all the pot holes we have on our roads?