Being a very new (less than 2 weeks) owner of a 2008 Civic Hybrid, I'm trying to think of all the things that affect mileage. Obviously a heavy load would make MPG worse, but how much? Has anyone experimented or kept detailed records of how the mileage varies with, for example, just the driver vs. driver plus one or two passengers?

 

I recently drove 140miles at 65-75mph with 5 people in the car, probably close to 800lbs with all of us and got just under 46mpg. I was kind of surprised at how little a difference it seemed to make. I could usually make the trip at 48-50mpg if only driving myself.

The single biggest difference maker I've seen is ambient temperature as you can read in a lot of other posts here. I lose 5-10mpg in the winter.

 

more weight means slower acceleration, lower top speed, and lower gas mileage.

 

I agree. Seems when I have someone else in the care I can tell a big difference in my mpg. Also, I can tell when the wind is blowing at me my mpg is lower.

 

Tire inflation is also a factor.

 

Welcome, Robin (I noticed this is your first post)!
And howdy, neighbor, to boot.
Mileage for all vehicles is poorer when the wind is blowing at you (headwinds).
I have a 2006 HCH2, and have not noticed a big drop-off in MPG when I have a passenger.
There is certainly some. I had 4 persons total in the car a couple weeks ago, and drove from Richardson to Forth Worth and back (80 miles or so, I guess). AC on, driving pretty much with traffic. I got 50 MPG for that round-trip. Alone, I might have had 53 MPG.

 

Don't forget that the purpose of the vehicle is to transport the people and things.
The person-miles per gallon almost doubles when you have a second person in the car.
One car with two people uses much less fuel than two people driving two separate cars,
even though that one car gets slightly less mpg than it would with only one person.

 

More weight = less mpg.

Simple.

But remember the "carpool effect" as mentioned above.

 

Our family of FIVE runs errands almost everyday in the HCH. Beyond the cursory kid fighting when crammed into the HCH, I've noticed significant differences in driving dynamics.

-MPG drops by about 2-3 mpg versus only myself as a passenger. I gladly accept this loss in my tank average because the alternative vehicle averages 19 mpg.

-The car rides 'heavier' and bottoms out more easily on large bumps.

-Acceleration is definitely slower with more assist necessary.

-The weight from five passengers increases your momentum and gives really strong regen. I try to use the extra weight to my advantage. I begin regen coming up to stops much earlier because the weight feels as though it's pushing the car. So if a particular stop requires 20 car lengths of no-brake regen to stop when I'm alone, then I try to increase that to 30 car lengths worth of regen when I'm fully loaded.

 

I agree that more weight equals less mpg but you can do a few things to counteract it. I drive by the IFCD and just adjust my foot to maintain the norm even when carrying additional weight. You will drive a little slower for it but not hugely so. Also, as Fly351 suggested, it does seem to give you more momentum in the car so use it to your advantage. Of course your tires will have to properly inflated to experience the increased coasting.

I don't have a lot of experience as I usually drive alone but spent a couple weeks with my folks, and while I didn't experience a large drop off in mpg, I did have to compensate with some fancy footwork.