Interesting Mileage Experiment

[marwady]

So I'm on the way up to the 'laws in Northern Michigan for Xmas and noticed how bad my mileage was. I normally can make the 250 mile trip on 1 tank with about a 1/4 to spare. I get about 30 miles from my destination and I need fuel....wtf? My MVIC (manual vehicle information system, otherwise known as my TI calculator) tells me I aveaged 16.7 mpg..not good.

This trip is almost all freeway driving and I set the cruise for a little over 75. I have read here that a fuse 11 pull cures some of these problems so, while I was up there, I pulled it and checked it on the way home. This time, much better at 20.8.

My question is, what does the fuse 11 pull do to make that much of a difference and what caused the mileage to go south in the first place? I am NOT using a tuner and no performance mods at all (except for a K&N drop in).

[Deep Lava]

So I'm on the way up to the 'laws in Northern Michigan for Xmas and noticed how bad my mileage was. I normally can make the 250 mile trip on 1 tank with about a 1/4 to spare. I get about 30 miles from my destination and I need fuel....wtf? My MVIC (manual vehicle information system, otherwise known as my TI calculator) tells me I aveaged 16.7 mpg..not good.

This trip is almost all freeway driving and I set the cruise for a little over 75. I have read here that a fuse 11 pull cures some of these problems so, while I was up there, I pulled it and checked it on the way home. This time, much better at 20.8.

My question is, what does the fuse 11 pull do to make that much of a difference and what caused the mileage to go south in the first place? I am NOT using a tuner and no performance mods at all (except for a K&N drop in).

At 75mph it only takes a slight headwind to cause the computer to disengages the MDS (which = about 5mpg). For me, 80mph on a calm day = MDS shut-off due to the load on the engine. So a 5mph headwind/tailwind can and will make a huge difference. Being winter, heading north "usually" = headwind and less MDS driving therfore more fuel consumption and south = tailwind and more MDS driving and less fuel consumption.

[quinn]

I noticed that also, that my car is much more likely to use the mds when I'm going slower than 75. Made the difference in a couple of mpg on my last trip.