Best highway speed for highest gas milage

[SenorAnderson]

I am making a transcontinental road trip in a couple of weeks and want to drive as cheaply as possible. I want to get the best fuel efficiency possible. I know fuel efficiency starts to drop drastically at 65mph but I don't want to go below 55mph. What speed between there has the best efficiency?

[Serstylz2]

55-60

[SenorAnderson]

Oh, I drive a I-4 if that helps.

[rediflex]

I too have the I-4. I usually go no lower than 55 on the expressway and keep it around 60, unless i need to pass. I've gotten a record so far of 410 miles out of a tank of gas, however, this was mixed expressway/city driving, but more expressway than city. Usually, I try to pay more attention to the RPMs than the speed. Keeping the RPMs even and as low as possible seems to work better than obsessing over the number on the speedometer. Good luck!

[qnz]

THats an informative first post!

[RAZ_76]

55-60

Exactly!

[rediflex]

Some other things I do to increase my fuel economy (and, incidentally, lower maintenance costs on the car) are avoiding braking unless I absolutely have to. I drive about 23 miles each way to one of my jobs, on a state route. I pass through 4 stoplights and two residential speed zones. Otherwise the speed limit is 55, and the only time I brake during the trip is for the lights. I think it annoys people when I let off the gas way before even the "reduced speed ahead" sign is readable, but I don't have to brake and hit the speed zone perfectly (important because one of the towns usually has a police cruiser parked just inside the zone.) I also avoid braking on the highway unless some jerk cuts me off or there is a light/stop sign at the end of an offramp. Circular onramps between interstates? People hate me. They pass me because I let off the gas early and coast the corner, and have caught back up to them by the end of the turn, because they went 70mph till the very last second and then had to jam on the brakes. I've had my 8g for almost 3 years and have only had to change the front brakes twice, and the last time I didn't even really need to yet, but I didn't want to have to do it in the winter. (I don't buy cheapie brake pads though.) I can't locate the article, but some of my techinques are right out of the hypermiling guide, I had no clue, I just found through trial and error that these things work well.

Edit: I forgot to add that I have an AT, and that I have never used the cruise control.... I don't even know how to activate it. (Not really, I do, but I just have no use for it. I may be lazy enough to have AT, but I prefer to work the pedals myself, thanks.)

[amdrocks]

i'd say 55-60 too

[varroa]

i've been travelling from Seattle, WA through Los Angeles, CA, directly to Greensboro, NC (about 3500 miles so far), with a 900 lbs trailer at average speed of about 70, resulting in about 25 mpg.

i believe that the galant's aerodynamics are so good that the "fuel efficiency starts dropping after 65mph" rule does not apply here.

back in 2005-06, i would go snowboarding, 100 miles each way, 70mph average, resulting in 30 mpg.

[Joshua42007]

THats an informative first post!

LOL right on

[mrg7243]

i've been travelling from Seattle, WA through Los Angeles, CA, directly to Greensboro, NC (about 3500 miles so far), with a 900 lbs trailer at average speed of about 70, resulting in about 25 mpg.

i believe that the galant's aerodynamics are so good that the "fuel efficiency starts dropping after 65mph" rule does not apply here.

back in 2005-06, i would go snowboarding, 100 miles each way, 70mph average, resulting in 30 mpg.

your towing a trailer???? how does the suspension like that??

[JoeRad]

its 50mph on the button, cant remember the figures but as your speed increases the forces wind, friction ect. increase x4 everytime you double your speed.

80 kph (50mph) uses 20% less fuel than 100kph (60 Mph). i guess these forces start making a difference after 80 kph

Imnot pulling these figures outta my ass, my work is car and saftey crazy and i only just read this the other day, can rmember the exact details just the speeds

I got 62mpg two weeks ago following these speeds, im all in km so tell me if this is right

405 km = 250 miles

15 litres = 3.9 gallons

Shit if thats right it cost me 5 euro per gallon

[Galant306m]

The maximum fuel efficiency of an automatic car is right at the speed where O/D kicks in, you will get the best gas mileage cursing at 40-43 mph.

[quicksilver22]

I got 420 miles/tank going between 70-72 mph on all highway driving w/ two complete stops and 2 pushed accelerations. I'm lucky if I get 330 now.

[varroa]

your towing a trailer???? how does the suspension like that??

sorry for threadjacking, OP.

but the suspension is handling this trip greatly. i mean, at 10 years old and 145000 miles, probably all the suspension is worn to a point anyways, but i am not noticing any differences from regular driving. i guess, a well-loaded trailer would contribute to that.


also, on the original topic: does anybody else feel like 4g64 has better power AND fuel efficiency right about 3100 rpm in the 4th gear (about 70 mph)? even more power at 3400 rpm (75-76 mph), but much more wind noise => more aerodynamic resistance, subjectively.

i mean, at 65mph (about 2600 rpm) i got no power and the fuel efficiency seems to be slightly lower.

[JoeRad]

Again think expoentially, the more your engine is revving the more force spinning it, the more force spinning it the less needed to spin faster,

at 2600 your on the low end of the power scale probably and youd notice slow accel , mid range prob about 3500-4000 you get better accel as you have enough momentum to counter your vehicles weight and wind resistence and such have a faster acceleration.

fuel efficientcy is relative to the power vs the load, it alight ass car would get better milage at those low revs then at higher probably, but all cars will have a spot depending on the weight ect. where they are most efficient, not always lower Rpms

BTW i have a 4g63 so im not sure where your 4g64 power band sits

[Isaurio]

Change oil before leaving. Use fuel injector cleaners before the trip if you have time change fuel filter and intake filter. And stay between 55 to 60. Also coming to a stop for like 5 to 10 min. Shut off the car. Making the car idle for that period will waste a lot of gas. The whole key to have better gas mileage is to keep your engine healthy and free of heavy loads. Shit like unnecessary thing have to go from your trunk.

[varroa]

Again think expoentially, the more your engine is revving the more force spinning it, the more force spinning it the less needed to spin faster,

at 2600 your on the low end of the power scale probably and youd notice slow accel , mid range prob about 3500-4000 you get better accel as you have enough momentum to counter your vehicles weight and wind resistence and such have a faster acceleration.

fuel efficientcy is relative to the power vs the load, it alight ass car would get better milage at those low revs then at higher probably, but all cars will have a spot depending on the weight ect. where they are most efficient, not always lower Rpms

BTW i have a 4g63 so im not sure where your 4g64 power band sits

well thanks for kind of supporting me, but my point was a little bit different. yes, there is more power the higher the RPMs get. but i was saying that, contrary to popular belief or whatever, but 8g's fuel economy gets BETTER as speed rises.

just last night i got back from an 800-mile trip: NYC to Richmond, VA and back with stops in D.C. THE WHOLE TIME my average fuel economy stayed at 29 mpg AND HIGHER. i was like "whaaaaa?". but seriously, with huge and long traffic jams on the way from NYC to Washington, D.C. and back, and traveling at 75-80 mph between the traffic jams, i still got 29.5 mpg. i don't even know how i did it. oh, and i was towing a 500 lbs trailer and had about a 100 lbs of other stuff in the car.

was it the wind? maybe. but both ways the wind was in my back? prreeaase.


anybody got a better explanation?

[AktionCat]

The maximum fuel efficiency of an automatic car is right at the speed where O/D kicks in, you will get the best gas mileage cursing at 40-43 mph.

you get best gas mileage cursing at 40-43 mph.

well thanks for kind of supporting me, but my point was a little bit different. yes, there is more power the higher the RPMs get. but i was saying that, contrary to popular belief or whatever, but 8g's fuel economy gets BETTER as speed rises.

just last night i got back from an 800-mile trip: NYC to Richmond, VA and back with stops in D.C. THE WHOLE TIME my average fuel economy stayed at 29 mpg AND HIGHER. i was like "whaaaaa?". but seriously, with huge and long traffic jams on the way from NYC to Washington, D.C. and back, and traveling at 75-80 mph between the traffic jams, i still got 29.5 mpg. i don't even know how i did it. oh, and i was towing a 500 lbs trailer and had about a 100 lbs of other stuff in the car.

was it the wind? maybe. but both ways the wind was in my back? prreeaase.


anybody got a better explanation?

prolly cuz down hills your trailer pushed u faster then your accelerating?

[03-Galant-ES]

you get best gas mileage cursing at 40-43 mph.

yeah cursing that you are at 40-43. I agree with joe rad that the G will be best around 50 its a somewhat decent speed and you will get great mileage and enjoy the ride. Do standard maintenance on the car before leaving, spark plugs may help and are cheap enough to change. Check tire pressure. Change oil. Change or clean air filter. If you don't have K&N air filter then possibly invest in one. Remove all unnecessary weight from car. Keep windows shut or AC off if possible. At high way speed I believe having windows open uses more gas then the AC on fan setting 1 so if its hot use the AC.