Slow is the way to go!
 

Well, I just completed a very interesting experiment.

I went to Spokane WA on Monday, worked there all week, and drove home today.

I filled up before heading out, and drove right at 70 mph +/- about 2 mph the whole way. When I got there the odo showed acouple of ticks under 300 miles, but since it reads 2% low the actual was 306 miles (verified by GPS). I filled up with 11.8 gallons for a total of 25.7 mpg. Not too impressive.

Then I drove around town all week. Mixed driving on city streets and the highway - but all 60 mph and under. I racked up 198 miles - which with a 2% adjustment is 203 actual miles - and when I filled up again before coming home this morning it took 7.2 gallons for a total of 28.2 mpg. Much better.

So as an experiment I decided to drive ALL the way home keeping it at 60 mph. I set my GPS to beep at me everytime my speed got up to 62. So for 4-1/2 hours I drove a steady 58-63 mph, and when I pulled into the gas station in my neighborhood, my odo showed 271 - which is 276 actual miles. I filled up and all I could get into the tank was 8.4 gallons! Even with rocking the car and doing everything I could to get it to take more.

That is an amazing 32.9 mpg! I know the last long trip I took I got just under 32 mpg driving an average of just under 65 mph - and everyone said my numbers couldn't be right. Well I KNOW this is correct. Averaging 60 mph is definitely the way to go if you want to maximize your mpg...

Great stuff!

I am going to try that next trip with my car.

Tom W

Maybie you would get even higher if you went 55mph.

Or 45mph.

lol, if you get a tall enough rear end and a 5 speed tranny, you might beable to idle at 60mph lol.

Well, I've been hearing rumblings about bringing back the 55 mph speed limit. If that happens, then I might try going slower, but for now 60 mph is as slow as I care to go. If I can break 30 diong 65, then that is good enough for me...

Excellent...notice how slow the trucks are going these days? Fleets have how governed the rigs to top out at 65, some go less...i went from chicago to detriot, and back..stayed in a trucks slipstream most of the time, not tailgaiting, but 'nearby'. Speed about 62, got about 38MPG. The scenery sucks traveling this way, but it does pay off. I would like to run a long-range test, doing 55. That would be a boring ride, but the results should be interesting.
Sad part is , with the price of diesel, you need to be getting solidly in the 30's to be traveling cheaper than the gas autos...diesel was 1.85 when i picked up the Benz, and gas was about 2.00. that was great for the wallet. Now, I have just picked up a Ford "ZX2", that is an escort, btw. Mileage after app. 500 mi. is 31.8, and that is suburban/city, not hiway. No way is the benz going to beat it in cost-per mile, unless I go WVO.

The aerodynamics of the W123 leave something to be desired, but it's sure good looking. :D

While I applaud your efforts at fuel efficiency, personally, I take the opposite tack when making a journey.

Here is why:

For the 300 mile stretch, your 60 mph jaunt took an additional 43 minutes.

However, you saved 2.56 gallons of fuel for the trip........approx. $12.

Effectively, the cost is $16.74 per hour of reduced trip time.

How much is your time worth?

If I'm going 550 miles on a business trip, the additional $25. in fuel to save about 80 minutes in total trip time is negligible in the overall scheme of things.

Fundamentally, this is the problem.......fuel is still too cheap.


I do reverse this logic on shorter trips. For a trip of 150 miles, the time savings is meaningless...........especially when it's not possible to hold 70mph for the entire trip due to traffic conditions.

Isn't going to Spokane kinda uphill and going to Skeddaddle kinda downhill?? :confused:

"fuel is still too cheap"? C'mon, it's too much..wait 'till this winter, when you get your heating bill. Anyone have a coal-burning furnace, circa 1910, for sale?

is that with the 3.07 rear gear? mine has the curse of the 3.47ish rear gear and going 60mph on long highway runs gives me about 25-27mpg. And yes slow is the way to go!!
CURSE the exponential increase in wind resistance with regards to speed.

F= (1/2)*ρ*v^2*A*C
F=force of wind resistance against the forward momentum
ρ=density of fluid (air is a fluid)
v=velocity
A=Frontal area
C=Drag coefficient

so yes slow is the way to go

Not exactly. Seattle's average elevation is 520 feet and Spokane's is 2000 feet. However, with 2 or 3 mountain passes in the 3000-5000 foot range, it isn't enough of a difference to amount to much. Especially since most of the elevation change takes place at Snoqualamie pass about 50 miles from Seattle.

Interesting point, and normally I would agree. However, this little experiment was on "company time" so the extra 43 minutes it took me was "paid time" ;)

Your point about the inability to hold 70 mph for the entire trip is also applicable since there are numerous areas where the interstate speed limit slows to 60 (or less in the case of road construction).

The one-way drive at 60 probably cost me an extra half hour...

BTW, a big part of the OVERALL improvement in mileage is no doubt due to the excellent job bgkast did on adjusting my valves during the tech session last weekend. Getting 28 mpg in mixed driving is nothing to sneeze at either - not to mention nearly 33 mpg on the long jaunt.

THANKS BRIAN!

You remember the cracked hose we saw? Well, it let go last night - fortunately really close to home when I was running errands - rather than somewhere over in eastern Washington yesterday! I fixed it today...

60 mph to save a few dollars, ok.
but can you put a price on boredom?:D