Gas Mileage Report

bobmbx · Dec 12, 2017

Last weekend, I drove from VA to FL and back. Roughly 1000 miles each way. On the way down I had the cruise control on 75 and averaged 18.5 MPG. On the way back the cruise control was set at 80, averaging 16.3 MPG. Thats a whopping 12 percent drop in fuel mileage.

I offer that as evidence that driving north is in fact, up hill.

chuck s · Dec 12, 2017

Air resistance is exponential and once rolling is a major, maybe the major resistance. No surprise that driving faster burns more fuel. I always seem to drive faster on the way home! Air resistance is why it takes obscene amounts of horsepower for even exotic sports cars to reach speeds over 150mph and few can push 200.

On a more practical level air resistance is twice as much at 70mph than than it was at 50mph.

And 14% more at 80mph than 75mph as you just demonstrated.

All in a perfect aerodynamic world.

And don't expect your fuel usage to drop 50% if you never exceed 50.

I found during my frequent drives from Cleveland to Gettysburg could be made in the same time with less fuel if I slowed down about 5 mph as I could do it on a single tank of fuel at the slower speed and the time spent at a refuel stop cost more time than I made up with faster road speed.

-- Chuck

Adieu · Dec 12, 2017

Wind n shit.

Also, 80 mph is a bad cruise control setting for most motors in most vehicles, air resistance notwithstanding.... if you have a 5.4 triton, afair its sweet spots are 64, 69, and 74

Whether that's speedo error or its specifically geared and mapped to have specific shift and RPM points corresponding to crusing at 65 70 and 75 as typical speed limits they assumed we'd stay just below, I'm not sure

deweysmith · Dec 12, 2017

I just drove from Montreal to SLC this weekend and most of the time had the cruise set on ~75 (120 km/h) and the computer says I got 14.4mpg.

JExpedition07 · Dec 12, 2017

Well with the cold air mass here in the north I’d think driving in Montreal you’d definelty see a drop in fuel mileage. MPG always drops in the cold.

Wahooslayer · Dec 12, 2017

To me, the biggest difference I notice with fuel economy is traffic. Lots of traffic improves mileage due to reduced air resistance (drafting), provided there isn't a great deal of slowing and speeding up. Also, wind direction plays a large role, a 10 mph head wind makes 80 like 90, and vice versa. Tuck in tight behind a semi and watch your mpg go way up.

deweysmith · Dec 12, 2017

Yeah, drafting can help a ton but when Apple Maps says your drive is 35 hours, the difference between 65 and 75 is a precious 3 hours that I don't have to deal with the kids

sjwelds · Dec 12, 2017

Yeah and who wants to stare at the a** end of an 18-wheeler all day.

Adieu · Dec 12, 2017

Drafting can be tricky, if you're used to it in a big lifted truck or low slammed sedan/coupe, beware that vice versa the intuitive following distance and choice of vehicle to draft will actually be COUNTERPRODUCTIVE

You gotta stick yourself in the low pressure zone, depending on your ride height and their ride height some spots behind them may actually be highly turbulent HIGH pressure zones

Frank Wilson · Dec 12, 2017

Adieu said:
Drafting can be tricky, if you're used to it in a big lifted truck or low slammed sedan/coupe, beware that vice versa the intuitive following distance and choice of vehicle to draft will actually be COUNTERPRODUCTIVE

You gotta stick yourself in the low pressure zone, depending on your ride height and their ride height some spots behind them may actually be highly turbulent HIGH pressure zones

I thought this was covered on a mythbusters episode years ago.
I think they said you would need to be a couple feet from the lead vehicle to increase mileage.

Using the tank top off method, I am at 11 around town. Highway is a massive leap to 15. But, I'm not adding the correction for the 35's.

Gas hurts, but, I knew going into a V8 El lifted 3/2 and 35's was not going to be a gas sipper. But, I can put a chain around that volt drivers house and drag it down the street

Gas Mileage Report

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