Is getting to 5th gear ASAP really more economical?


#1

My son and I both drive standard shift cars (me, Subaru Forester - him Ford Escort) and we have a difference of opinion regarding the use of 5th gear. I know that I’ve heard (on Car Talk) and read elsewhere that a car gets better gas mileage the higher gear it’s in and to get to 5th gear ASAP, to save gas as well as wear and tear on the engine. He was driving his car with me in (of course) the back seat at about 50mph in 4th gear and I asked why, stating my understanding of higher gears and lower RPMs. He pooh-poohed my comments and said he was taught to drive as tho there was an egg between his foot and the gas pedal to get the highest mileage and that the gear the engine is in is irrelevant. I still think I’m right. Any commnets I can use to back up my observation- or back off my criticism? Thanks a bunch from a concerned mother!


#2

As always, Dad’s & Mom’s are right!

If you can get to the highest gear as quickly as possible, the engine rotates less RPM’s per distance traveled, which saves fuel.

Tester


#3

It sounds like you’re more right than your son. You certainly don’t want to be driving for any distance at high RPMs, which wastes gas. On the other hand, you don’t want to “lug” the engine by upshifting at too low of speed, and having insufficient torque. That can even damage the engine. He’s right in the sense that you want to be gentle with the gas pedal and not mash it down, but that’s a separate issue from being in too low of gear.


#4

I shift into fifth as soon as the engine will pull it without lugging. What rpm the engine lugs at depends a lot on the throttle opening. At full throttle, you need to wait at least till you are going 50-60 mph before putting it in fifth, but if you are barely giving it gas, you can put it in fifth at 30 mph.

My last tank of gas (422 miles/9.574 gallons to fill up) was about 44 mpg in my Toyota Yaris. If your son gets better gas mileage than that, I will gladly listen to his advice.


#5

It sounds like a case of hearing one good point and disregarding all others. Not everybody knows about mechanical things. He could have been messing with you to see if you would say anything. I knew people like that.


#6

At 50 MPH there should be no problem with using 5th gear on any car.
At much lower speeds then it could vary depending on the type of car, load, engine, etc.

Every car has a powerband in which performance is best and if one lugs a car around at say 30 MPH in 5th gear then the mileage could very well suffer; especially on smaller, shorter stroke engines.
Think of taking a Ford Festiva and a Ford 5.0 Mustang, both with 5 speed manuals and similar gear ratios. Place each one in 5th gear at 30 MPH and start depressing the pedal. The Mustang will easily pull while the Festiva is going to buck and jerk its way to 40 MPH with barely any indication the speedo needle is moving.

I subscribe to the egg under the foot theory unless I’m driving my turbo SAAB and then it’s a bit difficult.


#7

An engine that is running at half throttle has a different powerband than the same engine running at full throttle and an engine running with the throttle only 10% open has a different powerband than one running at half throttle. That’s why automatic transmissions are programed to shift at lower engine rpms when the throttle is closed more.
The more the throttle is closed, the lower the maximum torque and horsepower rpms tend to be. When the throttle is closed to idle, both the max torque and max power rpms are lower than the engine’s no load idle rpm. Above the no load idle rpm, the engine is braking.


#8

Driving for the best mileage is both a science and an art.

The science part tells you that for any given driving condition (level driving, hills both up and down, accelerating, decelerating etc, there is a proper gear. However since all those things are happening at once and are dynamic, it is not easy to get it right all the time.

Now add in traffic conditions, traffic lights etc, it becomes an art to get everything right all the time.

While there may be some sort of car that would not have lower mileage in forth rather than fifth gear at 50 mph, I have never seen one. Shifting too soon for the specific car, rate of acceleration, and other conditions will reduce mileage and can damage the engine. Shifting too late will result in reduced mileage and can cause extra wear on the engine.


#9

I would say your son is right for automatic transmissions, and you are right for manuals. The light touch on the gas pedal will help, and in an automatic that will have it upshift ASAP, accomplishing what you are suggesting for a manual. Since the large majority of drivers have automatics, the “egg between your foot and the gas pedal” advice is fine for most drivers. With a manual transmission the driver has more responsibility to select the proper gear for best economy/power/acceleration depending on the situation.


#10

Your fathers egg theory is one part of the solution for good miles. Getting to the highest gear quickly is the other part. The trick is getting there quickly with low torque. I drive new beetle deisel. Using this method on open road gets me into high gear at around 30 mph. Gas mileage averages 62.5 mpg consistently. In stop & go driving the mpg is 53mpg consistently. Engine has 100,000 plus miles. I believe these figures are above the averages for this car.