Ideal MPH for ICE

So far you are doing well

 

Mid to high forties.

Tom

 

What about with a slight uphill grade?

 

Should be close to the same. At low speeds the ICE is under utilized, so the Prius has to resort to on and off use of electric power. At high speed aerodynamic drag kills mileage, so the ideal speed is somewhere in between - generally in the mid forties.

With a slight uphill the ICE still has plenty of power. As the grade increases, the ICE will need to work harder. As it approaches wide open throttle the efficiency drops off, so on a very steep hill speed may need to be lower.

Tom

 

I think the best efficiency comes with dynamic driving. You should plan ahead. So, if you see a hill, maybe gently increase your speed by a few mph. I usually try to speed up by 5-10, depending on conditions. This way, it will be easier for you to climb the hill and you won't have to hit the gas so hard while your actually doing the climbing to maintain speed. Then you can pretty much coast once you've reached the top.

 

Climbing a hill is not easier at higher speed. If you mean "taking a run at the hill" that is also not efficient unless it's a very short hill. If you want proof, try the interstates that cross the rockies. You will find you get your -worst- mileage climbing those hills (mountain pass) at interstate speeds!

I find amazing mileage is possible in spite of very steep grades if you can keep your speed in the 70-85 km/hr or 43-50 MPH range. For example, the "Duffy Lake" portion of highway 99 in British Columbia. Up to 17% grades, limit of 60 to 80 km/hr, up and down all the time with sharp corners (30 to 50 km/hr recommended on them depending on the corner). Pearl does much better on this road than the Coacahalla, which is a high speed "interstate type" highway with no sharp corners and grades limited to about 6%.

 

Yes, that's basically what I meant. I'm just talking about gaining some extra momentum to help get you over at decent speed.