Will removing a rear seat move the centre of gravity in a minivan too far forward?

A family member frequently drives around in the van all by themselves, which I'm sure is an enormous waste of gasoline. Removing one or both of the rear seats will help reduce the weight of the vehicle and improve the efficiency a tiny bit. That said, I was wondering if doing that would cause handling issues due to the centre of gravity being farther forward. Also, winter is long and icy here, so rear traction is an issue 5 months of the year.

Gorfram8 years ago
The good news is that removing the seats probably won't affect the handling much at all. The bad news is that it won't affect the gas mileage much either. Curb weight of a 2009 Toyota Sienna minivan is 4270 lb. Each seat probably weighs about 100-150 lb. which makes for about 3% of the total weight. But weight is only one factor in gas mileage - overcoming friction and resistance in the drive train and tire-&-wheel assemblies is probably a greater factor. It might be interesting to do a couple test runs - one with the driver in the minivan alone;, and then one with the minivan full of all the family members, friends, and sacks of potatoes you can easily get inside it - and compare gas mileages. (If after that you got the oil changed, made sure all the tires were properly inflated, and put in a new air filter, that mileage result might be interesting too.)
lemonie8 years ago
If it's one of those old VW mini vans it might.. The independent rear suspension isn't that sophisticated and rear-loading does affect handling. Like Gorfram I don't think a seat would make much difference though.

zalf (author)  lemonie8 years ago
Duly noted that it will provide a minimal boost in efficiency.

However, as Gorfram pointed out, each seat weighs 100-150 lbs, collectively 200-300 lbs. Basically, I see leaving those seats in as paying a fat guy a couple of bucks a month to sit in the back of your van.
Gorfram zalf8 years ago
I don't think you're paying that fat guy more than about a buck or so per month.

Let's say that the van makes a 40 mile round-trip 5 days a week. That's 200 miles/week, or 900 miles in a 4-1/2 week long month. Throw in 100 miles worth of errands and miscellany for a nice round 1000 miles/month.

Assuming 20 mpg, that's (1000 miles)/(20 mpg) = 50 gallons of gas/month.

Assuming gas is $3 per gallon: (50 gal)($3/gal) = $150/month (not unusual, but it's still gotta hurt).

If the fuel efficiency of the van depended only on its weight, then you'd be right:
3%($150/month) = $4.50/month

But that's wrong - our imaginary fat guy isn't getting paid nearly that much.

Fuel efficiency depends much more on the drive train than anything else. If you don't believe me, compare pushing the van when it's in neutral (you're pushing against rolling resistance, which is a direct function of gross weight) to pushing the van when it's in first gear (now you're pushing against the resistance to compression of the air in the cylinders, plus all the friction and inertia in the engine, and the rolling resistance).

My semi-wild guesstimate is that fuel efficiency can't be more than 15% to 20% dependent on rolling resistance/gross weight. If we take high end of that -

20%($4.50/month) = $0.90/month
(Our poor old fat guy must be pretty hard up for cash.)