Best speed for fuel economy?

[ThisIsMatt]

Originally posted by: Eli

Originally posted by: Cooljt1
the lowest rpm while cruising will normally give you the best gas mileage. also, not using ac or heater will also increase gas mileage

Running the heater doesen't effect your gas milage. It's "free" as far as energy goes, because it would just be wasted anyway.

The answer is probably largely going to depend on the engine, transmission gearing, and the drag of the car. Lower RPMs aren't *always* better, although it's not like you're going to be idling along at 1000RPM down the highway.

If you look at the fuel usage chart for an engine it looks kinda like a C turned on its back. Fuel usage starts out high, and then as the RPMs climb, it actually decreases as engine efficiency rises... And then slightly past a fast idle, it shoots skyward.. say 2500 - 3000RPM.

Running the heater does affect your gas milage. Maybe unnoticably, but anything electric (heater fan) is going to decrease your gas milage.

 

[Pepsi90919]

0 mph

 

[Viperoni]

Originally posted by: ThisIsMatt

Originally posted by: Eli

Originally posted by: Cooljt1
the lowest rpm while cruising will normally give you the best gas mileage. also, not using ac or heater will also increase gas mileage

Running the heater doesen't effect your gas milage. It's "free" as far as energy goes, because it would just be wasted anyway.

The answer is probably largely going to depend on the engine, transmission gearing, and the drag of the car. Lower RPMs aren't *always* better, although it's not like you're going to be idling along at 1000RPM down the highway.

If you look at the fuel usage chart for an engine it looks kinda like a C turned on its back. Fuel usage starts out high, and then as the RPMs climb, it actually decreases as engine efficiency rises... And then slightly past a fast idle, it shoots skyward.. say 2500 - 3000RPM.

Running the heater does affect your gas milage. Maybe unnoticably, but anything electric (heater fan) is going to decrease your gas milage.

I can't see your heater hurting any. It would only make the engine run a bit cooler, which might make more power...

 

[dullard]

I've always been told it is typically 50 - 55 mph. The engine does better at faster speeds if there wasn't wind, but the wind resistance moves the optimimum down to around 50 mph. Of course engine performance and wind resistance vary dramatically from vehicle to vehicle.

 

[ElFenix]

your motor is at its most efficient at its peak torque. the speed might be illegal in your highest gear, tho.

 

[Quixfire]

Tipe2 is right on the money. But for the original question, it is very depended on each vehicle because of their differences. You need to test your drive cycle and maintenance a controlled environment as much as possible. To give you an idea of what I mean I will use my own car as an example.

92 Escort GT 1.8L 5sp, I get the same MPG +/- 1 when driving 65-75 mph which 32 MPG. Once I go over that 75 MPH threshold my mileage begins to drop, 80 mph = 30 mpg, 85 = 28 mpg, 90 = 25 mpg. I did this test in period of four weeks tracking my vehicle average speed over a given distance tracking fuel consumption.

I know drive an average speed of 75mph on the freeway and get a consistence 32-33 mpg depending on the weather.

 

[acemcmac]

As fast as your 4 wheels will carry you... the longer you work, the more money you make... thus nullifying any kind of "efficiency" gain

 

[ThisIsMatt]

Originally posted by: Viperoni

Originally posted by: ThisIsMatt

Originally posted by: Eli

Originally posted by: Cooljt1
the lowest rpm while cruising will normally give you the best gas mileage. also, not using ac or heater will also increase gas mileage

Running the heater doesen't effect your gas milage. It's "free" as far as energy goes, because it would just be wasted anyway.

The answer is probably largely going to depend on the engine, transmission gearing, and the drag of the car. Lower RPMs aren't *always* better, although it's not like you're going to be idling along at 1000RPM down the highway.

If you look at the fuel usage chart for an engine it looks kinda like a C turned on its back. Fuel usage starts out high, and then as the RPMs climb, it actually decreases as engine efficiency rises... And then slightly past a fast idle, it shoots skyward.. say 2500 - 3000RPM.

Running the heater does affect your gas milage. Maybe unnoticably, but anything electric (heater fan) is going to decrease your gas milage.

I can't see your heater hurting any. It would only make the engine run a bit cooler, which might make more power...

Well, I'm assuming your heater requires the fan to be running, which is drawing power, inducing a load at your alternator, loading your engine, requiring more fuel.

 

[Ausm]

Originally posted by: Pepsi90919
0 mph

We have a winnar DING DING DING!!



Sysadmin

 

[Abzstrak]

Originally posted by: Sysadmin

Originally posted by: Pepsi90919
0 mph

We have a winnar DING DING DING!!



Sysadmin

Only if you more accurately say 0mph with the car shut off, if its running and going nowhere then ovbviously this is the WORST scenario.

 

[Asharus]

According to the little MPG thing on my dashboard, I get around 26MPG between 75-80MPH.

 

[Shawn]

Originally posted by: MAME
no less than 2k rpms (that would be near impossible anyway on a freeway) and no more than 3k

That will put you around 65mph with a 5 speed manual

lol, that sucks! I'm usually at around 4-5k rpms in 5th gear when I'm on the highway. I can't do less than 80....

 

[MaxDepth]

Speed=Zero. Best gas mileage evah.

 

[Triumph]

Originally posted by: Abzstrak

Originally posted by: Sysadmin

Originally posted by: Pepsi90919
0 mph

We have a winnar DING DING DING!!



Sysadmin

Only if you more accurately say 0mph with the car shut off, if its running and going nowhere then ovbviously this is the WORST scenario.

Yeah really. When you are idling, guess what your fuel economy is? ZERO miles per gallon.

 

[MAME]

Originally posted by: redly1

Originally posted by: MAME
no less than 2k rpms (that would be near impossible anyway on a freeway) and no more than 3k

That will put you around 65mph with a 5 speed manual

Bah, I had a Bonneville that would run 75MPH at 1900RPM
in fact, my van (same engine, similar tranny) will do the same

Different gear ratios for different cars. I've never seen a 5 speed or less car pull less than 2k rpms at 75 though.

 

[MAME]

Originally posted by: DurocShark
My Volvo gives its best mileage/time at around 70mph. The Fiero gets best mileage at around 80. My S10 got its best mileage at 80 as well. My old 1971 Ford LTD got its best mileage at 55.

It definitely depends on the car, though newer cars seem to be able to handle higher speeds more efficiently than older cars.

Of course, the BEST over speed is going to be around 40... whatever speed your car moves at while in the highest gear and rpm's are at a fast idle. heh

Let me assure you that your S10 would have gotten better mileage at lower speeds.

 

[TechnoKid]

I pull 2900rpm in fifth @80mph in my dad's '98 Audi A6 2.8 V6 30v fwd tiptronic. I get about 25+ mpg this way when only on the freeway. With mixed city, it drops to 20mpg avg.

 

[SilentZero]

I know that in the M3 I averaged around 15mpg, my wrx wagon gets around 18mpg or so w/ the performance tweaks, and the acura gets roughly 20. I dont take any of the cars above 70mph or so on the Highway and keep below 4,000 rpm's so that seems to work for me. The more constant the speed and keeping RPM's low will give you better mpg.

 

[MAME]

the wrx only pulled 18? that's horrible for a 4 banger

 

[Viperoni]

To whoever said that in top gear RPM's are between 2-3k rpm, according to Car and Driver, a 1994 Buick Roadmaster with it's 4 speed AOD tranny, pulls roughly 1300rpm with the torque convertor locked up... at 55mph. Getting an average of 22mpg. Highway max is about 25mpg.
Thanks inpart to it's 2.56 rear end gears, 0.70 4th gear... and it's 335lb-ft of torque @ 3200rpm coming from the detuned Corvette LT1
And it still runs 0-60 in 7.8s and the 1/4 in 16 flat @ 90mph.

 

[MAME]

Originally posted by: Viperoni
To whoever said that in top gear RPM's are between 2-3k rpm, according to Car and Driver, a 1994 Buick Roadmaster with it's 4 speed AOD tranny, pulls roughly 1300rpm with the torque convertor locked up... at 55mph. Getting an average of 22mpg. Highway max is about 25mpg.
Thanks inpart to it's 2.56 rear end gears, 0.70 4th gear... and it's 335lb-ft of torque @ 3200rpm coming from the detuned Corvette LT1
And it still runs 0-60 in 7.8s and the 1/4 in 16 flat @ 90mph.

That's pretty crazy. But seriously, for every car you can mention that pulls such low rpm's, I can name 20 that don't. There's always exceptopns to the rule!