Weight of driver and passangers

Not a huge role, unless we are talking persons over the Guinness World Record size. On the door sill, there is a guide as to max passenger weight and number. Payload is based on 150lbs people. (Someone will probably post the stamped sill plate numbers...)

I do know healthy people over 6'5" that weigh about 245lbs, so obviously that would affect loading.

I and some others regularly flew as passengers in small charter aircraft such as Cessna 210s; when I used to get stuck in the back seat so the 'big boys' could fit in the middle.

To answer the question, yes, extra weigh will affect your mileage.

 

passenger weight does matter. on my previous tank, i took 3 100 mile round trips with 5 people in the car and my mileage was the lowest its been since going to summer formula gas (53.9). in fact, it broke my string of 6 straight tanks of 59 mpg or higher.

on this tank, i have only one trip of 45 miles RT with same 5 people, im at 565 miles averaging 60.8 and mostly driving alone... a few two people trips mixed in with around town driving.

but that only illustrates the point that the Prius effectively uses the power available. so any kind of additional needs on the vehicle will affects its performance.

when you have a vehicle that you can load an extra 600 pounds and not see a noticable difference in mileage, that only means that you are wasting power everytime you drive alone. i may have a 5 passenger vehicle (rather comfortable according to the people in the back i might add) but most of my driving is solo.

 

What I found with 3 people and luggage in the car is that if you try to accelerate at the same rate that you do when the driver is the only occupant, you certainly do play hell with the mileage, but if you make allowances for the extra weight and accelerate more slowly, you can definitely maintain your normal high gas mileage. On the other hand, the increased weight also seems to increase the regeneration efficiency (more inertia?)- I saw more regen symbols with a loaded car than I've ever seen driving the same route by myself..

 

I would say weight plays a significant role, but not until you near or exceed the maximum payload. On a trip last fall from Phoenix to Temecula CA, we had 4 adults with minimum luggage for a total weight of around 850 lbs. Mileage was approx. 42 to 44 driving at 70 mph. However, on the drive back, we were now carrying 5 cases of wine! At a leisurly 65 mph I was only getting 38 to 39 mpg. The good news, even though we were far exceding the weight limits, the car never bottomed out or mis-behaved.

Dave

 

A friend told me the rule of thumb is that 10 lbs. of weight reduction is equivalent to an increase of 1/2 HP. That should give you an idea of the effect of weight on mileage.