What is more efficient for driving a 90 mile trip?

[captainm27]

I frequently travel arpox. 90 miles to visit a friend of my families. I was just wondering what is more efficient:

If I travel 55mph, it would take me about 98 minutes.
If I travel 65mph, it would take me about 83 minutes.
If I travel 75mph, it would take me about 72 minutes.

Can someone with a scanguage tell me what the avg fuel mpg it at 55, 65, and 75mph?

What I am trying to determine is if it's more efficient to go faster and get their quicker, or take it easy and get there later.

[SilverBack]

Why not just hop in the car and find out?

[Phaeton]

I commute 60 miles each way to work everyday. I've found if I stay at 60 I get the best mix of economy and time.
I've read on here many times that 55 is the optimum speed for fuel economy though.

[voodoo22]

Originally Posted by captainm27

I frequently travel arpox. 90 miles to visit a friend of my families. I was just wondering what is more efficient:

If I travel 55mph, it would take me about 98 minutes.
If I travel 65mph, it would take me about 83 minutes.
If I travel 75mph, it would take me about 72 minutes.

Can someone with a scanguage tell me what the avg fuel mpg it at 55, 65, and 75mph?

What I am trying to determine is if it's more efficient to go faster and get their quicker, or take it easy and get there later.

I do not have a scanguage, but I can tell you that if you drive in summer without using a/c for hwy driving at:

50-55mph you can easily achieve 50-54mpg
60-65mph will yield mid to high 40's
70-75mph will give you very low 40's and mostly high 30's.

Use the a/c and you could see these numbers drop by at least 10%. I travel at 50-55 with no a/c for the majority of my commute and get over 50 on every full tank when it's summer and am still, if I used a/c and traveled those same speeds I get mid to high 40's.

[thebarber]

55mph would certainly yeild better economy.....but it depends on how patient you are...

[nemelek]

I don't have a scan guage either. However on a few recent 240 mile round trips I got 42mpg doing 60-65 and 37mpg doing 70-75 mph. Since gas prices dropped my time is worth more than gas savings.

[b_hickman11]

I get 44 mpg in the summer(100+ degress) with AC and cruise set to 70 mph.

[Loren]

Slower is more economical without question.

You'll get as much as 38-40 at 70-75 mph. Up to maybe 45 at 65 mph, and you can get up to 50 mpg with speeds of 50-55 mph if you have a light foot.

If you have the time to kill, it's an interesting experiment.

[Kal-El]

He does bring up an interesting point that I've always thought about.

Going 55 will keep the engine running for approximately 26 minutes longer, thus burning fuel 26 minutes longer than if he drives 75. So the conundrum is finding out if the added wind resistance of going faster actually adds so much more work for the engine that it burns more fuel in 72 minutes than in 98 minutes.

[Loren]

Simple math, my friend.

90 mile trip:

80 mph = 1.1 hours = 36 mpg = 2.50 gallons
70 mph = 1.3 hours = 40 mpg = 2.25 gallons
60 mph = 1.5 hours = 45 mpg = 2.00 gallons
50 mph = 1.8 hours = 50 mpg = 1.80 gallons

[gid]

we find that driving state roads posted 55 m.p.h. or less make for better fuel economy than interstate . Both got their best m.p.g. of 44 , being 2008 5 speed manual liftback and the '08 4 speed automatic sedan . Neck and neck for overall mileage .

[gid]

with the state roads of 55 m.p.h. or less you can coast more as well . On interstate gas is applied more often to keep constant speed . May take little longer to reach destination , no big deal to us . Get to take in the sights at slower speeds too . Happy motorin' .

[talnlnky]

Originally Posted by Kal-El

He does bring up an interesting point that I've always thought about.

Going 55 will keep the engine running for approximately 26 minutes longer, thus burning fuel 26 minutes longer than if he drives 75. So the conundrum is finding out if the added wind resistance of going faster actually adds so much more work for the engine that it burns more fuel in 72 minutes than in 98 minutes.

I've thought about this too... and I think you only really improve the
"gallons per trip" by going faster when talking about slow speeds, say 25 or 35.

The difference in times at slower speeds is MUCH bigger than it is at high speeds. difference between 20 & 40 is a factor of 2. Difference between 50 & 75 is only 1.25.

but with slower speeds its really hard to tell if you get better mpg's due to time decreases, or if it is other factors... like different gears.

Another reason why I think faster speeds don't allow for better gallons per trip.'s by going highway speeds you now have a drastically increasing air resistance to battle, thus reducing efficiency.

[thebarber]

for me, it depends on how far im going as to how fast ill drive....though ill often take the hit on economy regardless...

but when im driving from the maritimes to southern ontario (1500kms (930mi)) ill DEFINITELY take the hit in economy and do 75 vs 55.....saves me like 2h of driving in the end....and in that case, 2h of my time is worth lots more than 5mpg

[captainm27]

Thanks all for the info. So basically, the faster the car travels, the more wind resistance / friction is has to overcome, and the engine has to work harder to compensate for that...

I'll be heading out again next week, so maybe I'll try one speed on the way there, and another on the way back.

[slvryaris]

I would just figure the slower one.

[JBIZZ]

If your time is valuable to you, pay the extra few dollars a tank in gas and go 75. If you make more than $6 an hour working, it may be more efficient to save your time.