# Does my cargo van get better gas mileage when fully loaded? **URL:** \ **Category:** Factual Questions\ **Created:** [July 30, 2014, 2:15am UTC](https://boards.straightdope.com/t/does-my-cargo-van-get-better-gas-mileage-when-fully-loaded/694389 "2014-07-30T02:15:45Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![bengangmo](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@bengangmo](https://boards.straightdope.com/u/bengangmo)\ **Post date:** [July 31, 2014, 10:32am UTC](https://boards.straightdope.com/t/does-my-cargo-van-get-better-gas-mileage-when-fully-loaded/694389/21 "2014-07-31T10:32:35Z")
> [@Manduck](#): > > My car has a dashboard display that shows the amount of fuel used on a trip. I’ve found that the same trip can use quite different amounts of fuel, even though I use my cruise control to stay at the same speed most or all of the way. I don’t carry cargo, so the main things that could be different are the wind and the temperature. The wind obviously can affect your mileage depending on whether it’s a headwind or tailwind, and the temperature can affect how hard your AC is working, which can impact your mileage as well. Air temperature can also affect how efficient your engine is working ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [July 31, 2014, 1:03pm UTC](https://boards.straightdope.com/t/does-my-cargo-van-get-better-gas-mileage-when-fully-loaded/694389/22 "2014-07-31T13:03:35Z")
Could this be possible - gears are a compromise, right? What if, at low load, the car’s optimal RPM was between 2 gears, and it chose the lower one. At heavy load, it was just right for a higher gear? ---
**Author:** ![Rachellelogram](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rachellelogram/32/8689_2.png) [@Rachellelogram](https://boards.straightdope.com/u/Rachellelogram)\ **Post date:** [July 31, 2014, 1:34pm UTC](https://boards.straightdope.com/t/does-my-cargo-van-get-better-gas-mileage-when-fully-loaded/694389/23 "2014-07-31T13:34:07Z")
Open/closed windows? Air conditioning on/off? Make sure you controlled for these variables, otherwise the results aren’t significant. ---
**Author:** ![leftfield6](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leftfield6/32/18780_2.png) [@leftfield6](https://boards.straightdope.com/u/leftfield6)\ **Post date:** [July 31, 2014, 1:44pm UTC](https://boards.straightdope.com/t/does-my-cargo-van-get-better-gas-mileage-when-fully-loaded/694389/24 "2014-07-31T13:44:26Z")
There are dozens of things (many of which other posters are throwing out there) that affect mileage, but the basics are that you simply can’t measure MPGs with any kind of accuracy using such a small sample size (a single round trip) and/or using the marks of your fuel gauge. The only way to really do it is the way fuelly.com works. You log every time you fill up (and for this to work, you need to fill up, no partials), and you log how many miles since your last fill up. It calculates your mileage for that tank, but also has data points showing long term consumption, trends, etc. [This](http://www.fuelly.com/car/subaru/outback/2006/leftfield6/271005) is an example. Actually this is my 2006 Outback. You can see the mpg of my last tank, and you can see trends. If you click “browse vehicles” in the left menu, you can look up real life examples of almost every car. Whenever I’m car shopping, I use this tool to see what real life mpgs are, don’t trust EPA or manufacturer estimates. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [July 31, 2014, 1:45pm UTC](https://boards.straightdope.com/t/does-my-cargo-van-get-better-gas-mileage-when-fully-loaded/694389/25 "2014-07-31T13:45:44Z")
Doesn’t a vehicle closer to the ground become more efficiently aerodynamic? If so, the loaded van might ride a little lower on the road, utilizing ground effect to improve air flow… But I doubt if it would be measurable in the case of a cargo van at highway speeds. [Previous page](https://boards.straightdope.com/t/does-my-cargo-van-get-better-gas-mileage-when-fully-loaded/694389.md?page=1)