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TDI Fuel Economy Discussions about increasing the fuel economy of your TDI engine. Non TDI related postings will be moved or removed.

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Old April 15th, 2012, 18:20   #31
Max Period
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CR engine
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GPS speed
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no passengers

DSG Data by Plus 3 Golfer:
2009 Jetta @ 8k miles
13-24C / 55-75 F
Powerservice

manual data by Rockwater:
2010 Wagon @ 1-1.5k miles
1-17 C / 33-62 F
Winter fuel

(original thread)


Note: 2 Gallons per 100 miles = 50 MPG (USA). 2.5 Gal / 100 mi = 40 MPG (USA). The very top end of the graph (3 Gal / 100 mi) = 33.3 MPG (USA).

From this graph, to attain a specific range of 50 MPG (USA), cruise at 62.5 MPH for DSG and 66 MPH for manual.
For 50 MPG (Imperial) specific range, cruise at 78.5 MPH for DSG and (about 81 MPH, graph ran out) for manual.
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Last edited by Max Period; April 18th, 2012 at 12:48.
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Old April 15th, 2012, 18:33   #32
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I've found that if I set the cruise at at 68-70mph(actual gps speed) I get a pretty consistent 53-54mpg and thats even with the AC on during the summer. When I experimented with setting the cruise at 60 mph, I was able to pull off a roughly 60 mpg average. I took a small economy hit when i went to 205 width tires.
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Old April 15th, 2012, 18:36   #33
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Hey, our new CR engines burn 14% more fuel (reduced to +7% for SCR Passats) than your 90 hp ALH...

Quote:
Originally Posted by Max Period View Post
Here I'm tallied the fuelly averages of 2009+ Jettas, 2004-2006 Jettas, 1998-2003 Jettas, and 2012 Passats.

Average L/100 km, weighted on distance driven, fuelly US MPGs for higher precision.
2009+: 6.198
2004-2008: 5.737
1998-2003: 5.440
2012 Passat: 5.837

Fuel consumption difference (compared to 1998-2003 Jetta):

2009+: +13.93%
2004-2008: +5.46%
1998-2003: +0.00%
2012 Passat: +7.28%

Fuel consumption difference (compared to CR Jettas)

2009+: +0.00%
2004-2008: -7.44%
1998-2003: -12.23%
2012 Passat: -5.84%
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Last edited by Max Period; April 15th, 2012 at 18:38.
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Old April 16th, 2012, 16:12   #34
kennethsime
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I recently drove to Phoenix @ 75 mph (72 actual speed). My 15-gallon tank lasted about 770 miles, and I got just over 51 mpg.

The only modification I've made is removing the fuel tank vent (ventectomy), making it easier/faster to fill the tank up all the way.

Normally, I average mid-40s.
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Old April 16th, 2012, 16:21   #35
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Quote:
Originally Posted by kennethsime View Post
I recently drove to Phoenix @ 75 mph (72 actual speed). My 15-gallon tank lasted about 770 miles, and I got just over 51 mpg.

The only modification I've made is removing the fuel tank vent (ventectomy), making it easier/faster to fill the tank up all the way.

Normally, I average mid-40s.
Imagine that, ~70 MPH = ~50 MPG. I see a pattern
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Old April 16th, 2012, 19:20   #36
ruking
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Quote:
Originally Posted by Bob_Fout View Post
Imagine that, ~70 MPH = ~50 MPG. I see a pattern
Not a thing wrong with 50 mpg @ 70 mph ! Indeed, I see a pattern also.

Last edited by ruking; April 16th, 2012 at 19:30.
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Old April 17th, 2012, 05:43   #37
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This close in my experience. Pretty accurate rule of thumb for MKIVs

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Originally Posted by MikeMars View Post
The forum's rule of thumb used to be '120 - speed = instantaneous MPG' on the highway, i.e., at 60mph you get 60mpg, at 75mph you would get 45mpg (on the flat, no wind, moderate temperatures, no A/C or heater, & engine already up to full temp).

I don't know if this rule applies to the Mk4. But it should at least give you an idea of the effect of speed on fuel consumption.
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Old April 17th, 2012, 08:17   #38
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Quote:
Originally Posted by TheHolyCobra View Post
Driving 75 mph ACTUAL (about 79-80 on the speedometer) I can get over 50 mpg.

In the summer in 80* heat, with a stuck thermostat and slipping clutch, I got 57.1 mpg hand calculated on a tank of about ~300 miles. Full tank of gas, no wide open throttle or AC during the trip, traveling at an actual 75 mph. Probably would have gotten over 60 mpg but there was actually about 5 miles of city driving and a shut down in there.

Car is modded with a tune (RC3), full 2.5" turboback exhaust with no cat or muffler, and tires were at about 45 psi. 235,000 miles on the car as well.
I am glad you mentioned this. Why is the speedo off? It reminds me of a motorcyle!

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Old April 19th, 2012, 09:24   #39
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http://forums.tdiclub.com/showthread...95#post3752795

Details regarding my MPG at 75MPH (Actually more like 76-77MPH)
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Old April 23rd, 2012, 11:39   #40
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As with everything, weight matters a little. How you drive with your foot matters a lot. Wind resistance plays some. Elevation. How the engine timing and some other mods are set. I have gotten 59 and 20 with the same car. One was driving from WY to MN with a full car doing 57 the whole way. The other was doing 75 with a very strong headwind, Car top carrier and a trailer with a 4wheeler on with a loaded car.
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Old April 23rd, 2012, 17:38   #41
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I'll throw my hat into the ring too I guess......

I commute anywhere from 100-200 miles daily depending on where I might be working...... Longest commute was like 380 or something. That sucked!

I generally keep with traffic, which tends to be 75 ish. Sometimes faster sometimes slower. Mornings usually are 70mph and evenings 75-80. Last tank i got 51.5.
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Old April 24th, 2012, 08:52   #42
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Quote:
Originally Posted by tditom View Post
So the new guy asks what speed yields 50 mpg, and you say you can get it at 90mph
Why not take the opportunity posed by his followup question to clarify that you calculated 50 mpg at 90 mph going downhill over a short period of time if that is true? Why answer his original question with some special, rare case that was not clocked over a full tank?

I call BS on anyone claiming 50 mpg @ 75 mph (unless they've modified their final drive ratio)
I've done it a few times, all it takes is some luck having tailwinds both ways based on adiabatic conditions.. From L.A to Phoenix during monsoon season on summer fuel, I've seen 70-75 mph trip most of the way in 95-115F temps with my A/C set on low in an ALH with 130 k miles on a motor with a 5 speed and an 11mm Injector pump.

I've heard that that 11mm pump can make a good sized difference in your MPG due to higher pressure and better atomization of fuel.
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Old April 24th, 2012, 09:17   #43
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I think the point made earlier about VARIANCE is a good one to keep in mind. I would humbly add that it is also good to review the Central limit theorem in these cases of MPG discussions.
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Old April 24th, 2012, 09:25   #44
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My 150hp ALH gets over 50 MPG's every time I would slit my wrists if I only got 40mpg's

Quote:
Originally Posted by Max Period View Post
Hey, our new CR engines burn 14% more fuel (reduced to +7% for SCR Passats) than your 90 hp ALH...
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Old April 24th, 2012, 09:28   #45
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Quote:
Originally Posted by ksteel8880 View Post
I am glad you mentioned this. Why is the speedo off? It reminds me of a motorcyle!

German Law,

http://www.caranddriver.com/features...ometer-scandal
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