optimal speed for the best mpg's

[hrsp]

was wondering how you know what speed will give you the best mpg's

i know every car and transmission is different just trying to get an estimate of the "optimal" speed for it...

[Reverend Cooper]

Floored

[chargedformula]

i have no facts to back this up, but i would think that you would get the best mpg at the lowest rpm's in your highest gear. i heard somewhere that the engine is more efficient there because your throttle blades will be open more, which eaquals less vacuum and less pumping losses. you dont want to go so low you are lugging it though.

[Prince Valiant]

Usually b/w 45-50 mph will be the car's most efficient.

Many will claim they get better mileage going faster...but usually when that's the case, one or two things is occurring:

1. They are overgeared, and could afford to gear down to a lower gear (If a gas engine "lugs", it needs to run very rich and reduce timing thus reducing efficiency). At 45-50mph, usually lugging isn't an issue in many automatic car; likewise, only a few manual trans equipped cars would run into this problem in their top gear (mostly the 6 speed equipped cars, with their ridiculous 0.50:1-0.62:1 top gear ratio's). With regards to automatics, many torque converter's aren't locked at speeds less than 45mph either...leading to less efficiency.

2. Many individual's driving style may change to a more impatient/frustrated nature driving at slower speeds...IE, more frequent throttle changes, little burst of acceleration, late braking...and in general, just less efficient driving. If the person ended up driving the same avg speed, but in a smooth/efficient manner, they'd usually get dramatically better mileage.

A lot of people who claim their car is most efficient at 70+mph are mostly correct...they probably do get better mileage at those speeds...but it's not their car that's become efficient at those speeds, it's their driving style becomes more efficient.

[1320PNY]

Every vehicle is a mathematical difference. From frontal area, drag, tire pressure and temperature, gearing, burn efficiencies, exhaust style, etc. I would believe running at 1500 to 1800 rpm in top gear in a V8 would be prime. I know most four cylinders work better between 2400 and 3000 rpm.

[Russ Jerome]

My 97 Lincoln will get 26 mpg at 72-74 mph, 23-24 anything under 70mph..
My 86 pickup will drink fuel faster than you can add it anything over 50mph.

Vehicles are so far off from one another ya realy need to poll other owners of your similar ride.

[Russ Jerome]

Edit: a DOHC 4.6 Lincoln display (proven very accurate) will still get over 12mpg with car running at 125mph governed speed limit....so I've read !

[Turbo-Triumph]

for an 86 plymouth fury with a bad transmission, you want to stay below 30mph.

[Yooformula]

on our trip I was trying many different styles for each tank and the best mpg I got was at 75mph turning 2400rpms, I got 17mpg 375 miles to a 22 gallons fill. At 55mph turning 1900rpms, I got 16mpgs 353 miles to a 22 gallon fill. this was in our yukon with 3.73's.

[Rocket Power]

I've heard that when your engine is near its torque peak you'll get the best mileage, but no idea if its true

[wikked]

I get about 25mpg going 65-70.
I get about 32mpg going ~55.


It is pretty boring going 55 though :l

[wrencher]

An easy way to find the good spot is a vacuum gauge.
The higher the manifold vacuum, the better the milage should be.
Lots of older BMW's & Mercedes used this in their 'economy' gauge.

[BoosTT]

In my old cadillac northstart I got the best mpg right when it shifted into 4th at 37mph.

[Al]

With my Olds, OD does not kick in till 45-46 mph. I'd also say that good fuel econ occurs after OD kicks in but it also drops beyond 60.

[SmokinRAM114]

In my cummins diesel truck anywhere under 2k rpms. 70mph I got the best of 26mpg. 780mi to 30gal
The vw gets the best of 55mpg around 65 2500rpm. I got 840mi to 15gal

[hrsp]

Wow I need more mpgs

[VroomPshhTsi]

I agree with Prince, somewhere between 45-55 works best for me. Anything over that and I believe wind resistance takes off a few mpgs (I believe it was 5 mpg per 10 mph if I recall right).

[Plum Crazy]

I used to watch Injector duty cycle when i had the ram, id try to keep it around 5-7% to get better gas milage, was able to squeeze 17.8 mpg @ 65 mph, and 24.4 @ 65 mph while drafting a semi.

[FoxStang]

Wow I need more mpgs

I concur.

My best observed millage in the Exploder was 18.92 over 401 miles doing a steady 72 or so most of the way. City millage is a crap shoot, anywhere from 13.07-16.21, the upper end of which is about 60% city, 40% freeway (at avg mph of 75-80).