tips for fuel economy

Ragdude

Veteran Member
Joined
Aug 18, 2021
Location
Phx
TDI
2015 VW Golf SEL TDi
Just a note; not all left foot brakers are idiots, I mean I’m sure lots of them probably are, with the number of idiots in the world in general lol, but I know from my work operating equipment you OFTEN need to use both feet (one on each pedal, the machines are made for this) for better and smoother control, and I can see how some people might end up making that a habit in their personal vehicle. I personally don’t do this unless the situation calls for it (like rocking the vehicle back and forth to get unstuck, things like that) and then only in vehicles with two pedals (naturally your left is busy with the clutch in cars with manual trans).
Ok my apologies to the .001% who fall into that catagory
 
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AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
AHU works the same. Using TDeanI's example:

he loses 1/4 mile of coasting by leaving it in gear. Coasting in neutral during that extra 1/4mile costs him about 0.12gal/hour * 0.0042hour, or 0.0005gal. Coasting in 5th saves him 0.0005gal, but costs him much more than that to regain his original speed.
We all have a regular routine with our drives, including basically the same routes to work, grocery, hardware store, etc. I learned that there are places along those routes where it is best to coast in gear vs in neutral. I live out in the county 17 miles from town. On the route into town there is a section of highway with a 2.5 mile up hill grade and just over 4 miles down hill on the other side. It is not safe in either direction to coast in neutral due to the curves. I drove that section of highway for over 33 years in my career commuting to work. Then, a major road rebuild and alignment resulted in a nice long stretch on both sides that can be negotiated in neutral in both directions. But, I prefer just coasting in gear and practice that method as a way to slow the vehicle before a stop sign, traffic light, a need to merge in some circumstances, negotiating curves, etc.
 

TDeanI

Veteran Member
Joined
Oct 14, 2007
Location
Bremerton WA
TDI
'97 Passat TDI Wagon w/ 286K mi.
I can tell you that my coasting technique is worth 5 mpg for my car on my daily commute. I do not coast below the speed limit. I coast down to the speed limit or just under it. With my taller gear it makes it harder to accelerate at 50 mph in 5th and I waste fuel building boost or shifting to 4th. There are plenty of hills where I can maintain speed in neutral or accelerate. I put it back into gear or let out the clutch slowly when down to the speed limit.
On my 35 mile trip to work, I added up all my coasts and it was an easy 5 miles of total coasting if I add up all the big and medium coasts in 35 miles. Lots of hills but only a few steep ones where I need to brake. I have two coasts i can coast for over a mile. In gear, the same coasts are less than 1/4 mile. My coast in gear are only around 100 mpg on my Scan Gauge. My coast in nuetral are 360-450 mpg.

On days that I am late and just follow the car in front of me driving normal and leaving it in gear, I get maybe 47 mpg for the same trip. At the same speed I get 52-56 mpg same trip with coasting. Five miles of coasting while getting 400 mpg saves fuel.

My car has substantial aero mods so I can coast farther than stock vehicles.
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Coasts in gear should turn off all fuel feed in my understanding. Should be infinite when coasting in gear.
Yeah, the Scan Gauge in my Jetta's go to flat line coasting in gear, indicating fuel totally turned off. The Gasser Engine in my 2011 VW Tiguan will show the same on the in-dash indicator. And, even though it it is a 6-speed automatic, coasting in gear when and where I can does improve them MPGs. Rather than MPGs with my Jetta vs the Tiguan, I look at cost of fuel per mile to drive them. In recent years, there's been little difference the TDI wins out!

Back in the day, that long 4+ miles of down hill coast I mentioned above, would result in the Temp Gauge dropping noticeably on a very cold morning on the way to work. So, that is solid proof the fuel is shut-off during coasting in gear.
 

turbodieseldyke

Veteran Member
Joined
Jun 6, 2010
Location
Free Mustache Rides
TDI
98 jetta
On my 35 mile trip to work, I added up all my coasts and it was an easy 5 miles of total coasting if I add up all the big and medium coasts in 35 miles.
When i used to drive up the Grapevine every week (I-5, south of Bakersfield), I used a stopwatch to track my bursts of In-Gear-Foot-On-Gas-Pedal time during the Neutral coasting. From the summit (4144ft), i could make it 20 miles with 90 seconds of Pedal-Time. I'd guess the final elevation petered out around 500ft.
 
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