My trip to work can take one of two routes: The interstate or a two-lane highway. The interstate is 26 miles, speed limit is 70, and is relatively flat and straight. However, it is a toll road and costs me $1.40 each day to drive there and back. The two lane highway, however, is very curvy and hilly, speed limit is 55, and is slightly longer at 27 miles.
I drive a 1998 Ford Explorer, 4.0 liter V6 SOHC, 4 wheel drive. I've only worked at my job for 3 weeks so I haven't been able to do a ton of testing yet. However, I hate the interstate because of the toll, and plus the curvy two lane road is so much more fun to drive. On my last tank of gas, solely on the two lane road (with a bit of in-town driving), I got 19.5 mpg with my cruise control set at 55. Based on that and taking into account the toll, I figured I would have to get 21.5 mpg on the interstate to make the cost difference worth it. I kinda find that unlikely. The best mpg I've ever gotten was 24 when I was going 65 mph for 3 hours with no stops or in-town driving on relatively flat ground. I usually only get 13 mpg in-town, even though I'm a very conservative driver. I don't do hypermiler stuff, but I coast to every stop light, only go the speed limit, etc. So I figured I wouldn't be able to make 21.5 mpg because even the little in-town driving I do kills my mileage. What do you think?
But my most pressing question of this thread deals with how to drive on the hilly two lane road. If I keep my cruise control on, it keeps me between 53 and 57 mph. Sometimes it has to do this by engine braking on large downhills or downshifting an average of two times per trip on uphills. This week I've decided to try a new strategy, and that is to keep the cruise control off and let the hills guide me, more or less. I keep it from downshifting on uphill routes, even though it sometimes drops my speed to 45 mph. and on downhill I just let it coast in gear, sometimes it gets up to 62 mph or so. So my real question is, which is probably more effective? cruise control off or on? I've heard that your injectors can basically close off if the engine doesn't need to produce more power, so I figured cruise control might help with that on the downhill when I reach the maximum speed my car wants to go. But if I just let off the gas, the rpm's go up with the speed, which I wonder if that takes more gas.
Take the scenic route. There are things worth more than a couple dollars worth of gas.
I personally would use the Pulse & Glide strategy, but the strategy you describe using a constant throttle position is called DWL (Driving With Load) and is regarded as very effective by some.
Using zero fuel while engine-braking is called "Deceleration Fuel Cut Off" (DFCO) and is very cool, but it may not be programmed very aggressively in your 1998 Explorer. Either way, it's best taken advantage of when you intend to slow or stop; if you intend to keep going, it's better to coast in neutral. You lose less speed, and the gas you spend idling is less than the gas you'd spend re-accelerating.
I'm a little afraid of shifting into neutral and back again. The hills aren't very big at all, most are 20, 30 feet at the most, and they roll. Once you're out of a decline you're back into an incline right away.
Thanks for the fast reply. I had picked over some of the recent threads in the forums, but maybe I should read the stickies too .
The highway vs. tollway comparison fails to consider the value of your time. How much longer does it take you by taking the 55 mph highway? Rounding up, I'm guessing 10 minutes. So assuming you could spend that extra 10 minutes at work getting paid, or that your time is worth $x/hr, that ten minutes is a cost equivalent to 1/6 of your hourly wage wasted each trip.
So if you make $18/hr, it actually costs you $3 worth of your time to take the slower way. Subtract the toll from that for the true cost of your time there.
I know, it completely ignores the entertainment factor of taking the slower route, but when both routes seem equally tired, your time really is worth something too.
actually it only takes about 2 minutes longer. So pretty much neglegable. That was one of the first things I checked. I'd rather sleep longer and take the toll road if it was too much longer. The toll booths really slow you down, because you're stopped while 3-4 cars in front of you do their thing.
I tried shifting into neutral for a while. It gave me the willies. I just got the feeling that nothing good would come of it. I also quit shutting the engine off at stop lights. I have two stoplights on the way to work that I have measured (1 minute and 1 minute 20 seconds). But my ScanGauge (do you have a ScanGauge?) says idling fuel consumption is .37 gallons per hour. So the minute saves me .006 gallons. Then when I start the engine revs and probably takes half of that back.
I don't think Ford believed in DFCO. The late '90s SUV design teams weren't wrapped around the axle for fuel efficiency.
Cruise control pretty much goes bye-bye on hills. I don't want engine braking (unless I'm going down a mountain, or there is a constable at the bottom. My rule is speed limit + 9). And it will downshift going up hills where I can keep it in high gear by loosing 5 mph. I used to think that maintaining constant speed was the mark of a good driver. But the goals have changed.
ScanGauge ($169 including shipping) makes going to work a game. It let's you compare each day's mileage to your previous best instead of burning a tank of gas to see how well you've done, which has to be diluted with all the other driving you do. This allows better evaluation of your driving technique.
I don't have a scanguage. I had never heard of them before I signed up to this site just a few days ago, so I really don't know anything about them. $169 is a bit steep, but it would be interesting to see my fuel consumption in real-time.
Do you have the V6 escape? Those look nice but I'm afraid I might not fit well in them (I'm 6'3"). I recommended my gf get one as her next vehicle once she gets out of college. She wants the hybrid.