Does Honda’s grade logic unnecesssarily burn gas by using the engine to brake on downhills?
No. I haven’t heard of “grade logic” (“Hey prof, I deserved an A because I didn’t fall asleep during your lectures!”), but I’m assuming it’s the transmission downshifting to use engine braking on hills? That’s the proper way to control speed on long downhill grades, not riding your brakes. As far as fuel use goes, the engine is basically idling – just enough fuel to keep the thing running, without adding to your speed. The engine is turning fast, but for the most part it’s pumping air.
I’ve had 2 Honda Accords with grade logic, a '97 and a '98. I don’t believe it burns any more gas when it downshifts on a downhill. The tranny will hold the lower gear as long as you don’t touch the gas pedal. As soon as you touch the gas pedal it upshifts.
If it comes with the CVT transmission, it is a good idea because the CVT will freewheel fastly downwardly quickly, causing the driver to get brakily with it. I would rather gain some speed and use the brakes when necessary but it won’t waste that much gas downhill because it doesn’t take a lot to go downhill.
I do the same thing with my manual transmission. It does not burn any more gas than idling the engine, and, with some newer ECM programming, uses less fuel. It simply uses engine braking to effectively control your downhill speed, rather than you having to use brakes that can overheat. Overheated brakes will lose their effectiveness and require a brake job to correct.
Engine braking uses the engine’s compression power, exaggerated by the fact that no air is allowed into the engine through the throttle, as a braking force. The grade logic uses this ‘free’ braking through the transmission and drivetrain. No damage is being done. Motor happy!
Its actually supposed to burn less gas. It is supposed to keep your car in a higher gear when going up hill at light throttle. It delays the downshift until it becomes absolutely necessary. It is also supposed to hole the lower gear if you head downhill without touching the gas, but I’ve never seen it downshift to do this.
Correction: It keeps the transmission in a “lower” gear when going uphill at light throttle.
The transmission will downshift sometimes when the driver touches the brakes. Downshifting is inconsistent.
No, I got it right the first time, but maybe I wasn’t clear. If you are traveling on flat ground and come to a slight uphill grade, it will hold the higher gear (lower numerical ratio) that is it will stay in 4th gear instead of downshifting. This saves gas as well as wear and tear on the engine and transmission. On a steeper grade, it will delay the downshift to the last possible minute in case you reach the crest before it is needed.