I currently drive a 2004 Honda Pilot, great car, but i’m curious about my fuel efficiency. I drive around 40 miles to school and, 40 miles back. One day I was using the cruise control and going up a 50 mph speed limit hill (and keeping to that speed) and was starting to slow down a little so using the steering wheel control I accelerated a bit. The car, sounded like it, went through four gears and the revs shot up. For a little test, the next day I did the same only I wasn’t in cruise control and I was using the gas pedal. This time it shifted through one gear and the revs increased a little bit. That got me thinking and here’s the question. What gives me better fuel efficiency on average, using the cruise control of the pedals?
Sorry I meant to say in the last sentence “cruise control OR the pedals”
Cruise control. It shifts at the optimum points. While you might feel that your shifting was optimal, the cruise control system has no feelings at all. It simply responds to actual sensor signals.
On hill and dale roads, leave the cruise control off and drive the car yourself. That way you can just let the hill slow your car down a little going up hills and speed up a little going down hills.
No matter how smart the cruise contol is, only you can see how much hill is still ahead of the car and decide how to drive it for best economy.
Cruise control is better on the flat, because it keeps speed more constant than your foot can, and a steady speed is more efficient than constant slight acceleration and deceleration. On hills, you will get better mileage if you disengage the cruise and allow the speed to drift lower, but this is not always safe to do. Trying to accelerate on a hill (which kicked you into a lower gear) is the least efficient of all.
Our Honda Element does exactly what you describe if I encounter a rather long and steep hill with the cruise control on.
On this car, and probably on yours also, you can click the cruise control speed up and down one mph at a time with the buttons on the steering wheel.
Sometimes, If I see this situation coming, I will click the speed down one mph at a time as I climb the hill, giving the cruise control permission to let the car slow down, and then it doesn’t suddenly kick into a 5000 rpm passing gear right as I’m nearly at the crest of the hill anyway. Then as the car goes down the hill, I click back up to my original speed setting one mph at a time.
You can sometimes prevent this extreme downshift by manually locking out the overdrive as you go up the hill, forcing this one gear downshift usually results in the car being able to maintain cruising speed and not needing to do the “I’m passing a car” type of downshift to maintain cruising speed. Just don’t forget to undo the OD lockout as you go back to the level road part of your trip.
The transmission doesn’t know whether cruise control or your foot is driving the car and the increasing throttle opening that the cruise control does as you climb a steep grade is the same thing as you suddenly flooring the gas pedal to pass a car to the transmission.
Some cruise controls aren’t so smart.
They will just go wide open throttle to try to reach/keep the set speed.
Then the transmission responds the same as if you floored it.
As others say on hills it’s more efficient to manually keep the engine power moderate and let the car vary in speed.
It’s not an issue with a manual trans.
I’ll cancel the cruise on my Odyssey if a big hill is coming up to avoid the downshift and surge in gas & rpms. A gentle foot seems more fuel efficient on hills vs. a harsh response from the cruise.