Year: 2001
Tire Size: 265/70R16
Modifications that affect MPG: stock except removal of the "spoiler"? over the 3rd brake light
32 PSI, fresh 80w-90 in differential
Have NOT cleaned the MAF in forever. I hear that helps. Will clean mine and report back after next road trip.
{update}
I'm amazed at the impact of cleaning the MAF and driving a bit slower.
Before, I was at 20.5 MPG at 65 MPH.
After cleaning the MAF...
24.2 and 24.9 MPG (2 tanks) Speed: 60-65 MPH
That's equivalent to about 20% lower cost, or paying about $2.40 per gallon if it's at $3.00
These were highway-only miles (no city driving, etc.) Distances were 191 miles and 221 miles, fairly level interstate highway (I-5 in Oregon and Washington, no mountain passes.)
This was calculated by filling the tank and reset the odometer, drive, then dividing miles driven by gallons used to refill the tank. Just to be sure, the pump was made to "click off" 2 or 3 times on the refill. (Don't do this, it could flood & ruin your charcoal canister and turn on your CEL; but that's another story.)
Besides cleaning the MAF, see the other poster's message about wind resistance and increased air density in winter. In general, wind resistance is the square of velocity for objects the size of cars and trucks. In general, this means that doubling the speed increases wind resistance (drag) by 4 times.
http://www.toyota-4runner.org/3rd-gen-t4rs/248374-what-your-highway-mpgs-5.html#post2871670
1200 HP example:
www.physicsforums.com/threads/the-force-of-drag-is-proportional-to-velocity.372972/
How do I prevent the embarrassment of going 65 MPH or less on a freeway? Find a semi 18-wheeler going about the speed that I want, and follow it for 200 miles. Everyone just passes you and the semi. Be very polite. Follow 100-200 feet behind. (This reduces the rock chips, too.) Preferably it's an empty semi, so you can maintain speed going up hills.
Cleaning the MAF - the method below is if your screws are rusted and/or you don't have a stubby or right-angle phillips. Mine was just two small screws and using the special cleaner. If you screw up, it's expensive to replace. (I found the MAF cleaner at Walmart.) Removing the EFI relay for 20 minutes in my 2001 did nothing for resetting my computer (readiness monitors on OBD scanguage were all still OK), so I took the new mileage readings after having driven 2000 miles of city/highway.
Toyota 4Runner Highlander Mass Air Flow Sensor MAF cleaning
IMG_7559 by Brandon Faliszewski, on Flickr
. That's at 77 mph. Closer to 18 mpg at 74 mph, which I was able to do once thanks to crappy visibility conditions. Can't go any slower on I-5 or I'd get run over by 18 wheelers.
