Edited to add: I should note that this is a different strategy than using DFCO during the glide (see this thread). This is about when to switch between the two.
This will mainly be for automatic transmissions, since manuals can coast with the engine off (no fuel). Though, this may somewhat apply to manuals to help minimize wear on brakes and increase average speed.
A lot of you may already do this, but I thought I would share some techniques I've been trying to improve on lately for those who may be interested. It involves using P&G and DFCO more efficiently by not only timing them correctly at the correct speed, but also switching in and out of them during certain approaches/stops to increase your mpg.
Let's say you've got a long, flat stretch of road that ends with a stop sign. Hypothetically, there's no traffic to worry about. Let's also say it's about a 1 mile stretch of road. Here are some possible options you might choose:
1. Steady speed in gear, DFCO to a stop.
2. Steady speed in gear, coast to a stop.
3. Pulse and then glide all the way to the stop without shifting back into gear.
4. Pulse and Glide, DFCO to a stop.
Your mpg would look something like this for each scenario (this is just theoretical):
1. |----------------------------55mpg-----------------------------|---9999mpg---|
2. |---------------------55mpg---------------|-----------------220mpg------------|
3. |-30mpg-|--------------------------------230mpg-------------------------------|
4. |---30mpg---|--------------------250mpg---------------------|---9999mpg---|
The slightly higher mpg in 4 would be the result of a slightly longer pulse and higher speed.
Theoretically, if you're using an automatic and coast with the engine on, the best option may be 4. Sure, you could not pulse much in option 3 and glide at a slow speed all the way to the stop and barely have to brake. However, this will make for a very slow trip. If you pulse briefly up to a decent speed, glide, and then shift into gear to utilize DFCO at the stop, the fuel cut off time might offset the fuel spent during pulse, and
you'll arrive quicker and still barely have to use the brakes.
Not only can this be very fuel efficient, you'll be less likely to piss people off behind you, because you can maintain a slightly higher speed. This is something I've been trying to work on, because I deliver pizza, and it pays to do as many deliveries per hour as possible and keep a higher average speed.
Here are some other scenarios where you can combine Pulse and Glide and DFCO to increase your mpg.
1. A steep downhill that flattens out for a while and ends with a stop sign.
Strategy: Start with DFCO at the top. Once you've gotten far enough down the hill to start gliding and not speed too much, start coasting. Hold the coast until it's the perfect time to start DFCO to the stop sign.
2. A stop light around a bend that you can't see that happens to be red 9 times out of 10.
Strategy: P&G well before the approach. When you start to approach the bend, shift into gear and DFCO to cut fuel off and slow down a bit. If light is red, you saved fuel. If light is green and you make it, pulse back up to speed and prepare for another glide. You will have spent some fuel, but you only make it on green once out of every 10 times. On average, this strategy should save you fuel in the long run.
3. Steep downhill with no stop later on.
Strategy: Start with DFCO at the top. Once you've gotten far enough down the hill to start gliding and not speed too much, start coasting.
When doing these strategies, if your vehicle doesn't go into DFCO after shifting into gear from neutral or letting off the throttle, try blipping the throttle. This should initiate DFCO.
Since starting these strategies, I'm currently on track to beat my best tank of 43mpg (automatic transmission delivery driving).
Please feel free to add to or critique any of this. I'm always looking to improve.
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