best RPM for fuel economy?

[torpedo]

I was under an impression that high RPM will burn more gas. But is this entirely true? low RPM could make engine work harder, ie every stroke will burn more gas, but less # of strokes. What is the best for both engine life and fuel economy?
I always try to keep between 1400 to 3000 for normal city driving, and on highways no more than 3200 - 3500. Occasionally, downshifting from 4 - 2 , I reach 4000, but that's only momentary. So what is the best RPM level for each gear?

 

[outpost22]

Just DRIVING this car is economy driving for me. You should see what "economy" my V10 gets

Less RPM's= less air/gas volume=better economy except in extreme conditions (lugging) IMHO

I'm sure a guru will come along and prove me wrong

 

[chsu74]

I was under an impression that high RPM will burn more gas. But is this entirely true? low RPM could make engine work harder, ie every stroke will burn more gas, but less # of strokes. What is the best for both engine life and fuel economy?
I always try to keep between 1400 to 3000 for normal city driving, and on highways no more than 3200 - 3500. Occasionally, downshifting from 4 - 2 , I reach 4000, but that's only momentary. So what is the best RPM level for each gear?

There is an econometer in your RPM guage. Running through each gear through out the RPMs will give you the best MPG for each gear. It also depends if you are going up a hill or down one. It is different for every situtation.

 

[Average Jae]

rolling in neutral??

if you can coast along that's the best way to save fuel. even if you are in the lower rpm at the highest gear (6th in my case) it'll waste more gas than being at a higher rpm in 5th, because trying to pull from 1500 rpm at 50mph will need more engine work than acceling in 5th around 2k rpm, which is easier. thus lower gear may actually have better fuel economy. imo

 

[MrElussive]

Yeah, at first I thought that no matter what, the highest gear you can be in, the best fuel economy you will get. But sometimes, on the highway, I find it better to downshift to 5th when traffic slows down a bit, rather than trying to accelerate in 6th (according to my fuel economy meter). I completely agree with Jae on this one...sometimes it's better for the lower gear because the engine just doesn't have to work as hard.
One thing for manual transmission people: let's say you downshift and your engine is spinning at 4,000rpm, and your foot is not on the accelerator (let's say you're just rolling down the hill, relying on engine compression), you're actually wasting only very little gas. This is because the tires are powering the engine and all. That's why when let's say you're in 1st gear and you let go of the gas and then step on it again, you feel a noticeable "jerk"...it is the fuel line going back on or whatever. I'm sorry I explained this poorly, frolf knows how to say it best. My point is, if you're at like 3,000 or 4,000rpm and not using the accelerator, you're using very little gas...it's like using the same amount of gas in neutral, except you've got engine compression to slow your ass down !!

 

[frolf]

rolling in neutral??

if you can coast along that's the best way to save fuel. even if you are in the lower rpm at the highest gear (6th in my case) it'll waste more gas than being at a higher rpm in 5th, because trying to pull from 1500 rpm at 50mph will need more engine work than acceling in 5th around 2k rpm, which is easier. thus lower gear may actually have better fuel economy. imo

yeah, lugging your engine not only costs more gas, but is rough on your engine. i usually always keep the tach between 2k and 6k. freeway crsuing at like 60mph will get you the best mileage, above that you start to push up to around 3000rpm and lose a couple milespergallon. (i still usually cruise at around 75)

down highways (45mph speed limit) i usually leave it in 4th gear unless i am decending.

 

[RedShift]

Another thing to take in to consideration is that the new 330s all have 6 speed transmissions (manuals of course) with overdrive and they don't get any better mileage than the 5 speeds that have a 1:1 ratio (no overdrive).

 

[frolf]

in a 5 speed 4th gear is 1:1 i believe. 5th is overdrive.

 

[Akakubi]

in a 5 speed 4th gear is 1:1 i believe. 5th is overdrive.

Nope, the 5th is 1:1, we don't have an overdrive. Still get 32MPG on the highway travelling with 3 people, aircon and 70-80MPH.

 

[jrt67ss350]

Just DRIVING this car is economy driving for me. You should see what "economy" my V10 gets

Less RPM's= less air/gas volume=better economy except in extreme conditions (lugging) IMHO

I'm sure a guru will come along and prove me wrong

I hear ya! My Camaro, which was my daily driver before I got my BMW only got 9 mpg in the city (on a good day and only when keeping my foot out of it) and about 15 - 16 mpg on the interstate at 70 mph.

I agree with what everyone has said here - I think lower rpms are generally more efficient as long as you aren't making the engine to work hard to accelerate. So, when crusing at a constant speed on the interstate, your highest gear will usually be the most fuel efficient. In town with variations in speed and rolling hills, however, a lower gear may be more efficient since the engine doesn't have to work as hard to accelerate or maintain a speed.

 

[frolf]

Nope, the 5th is 1:1, we don't have an overdrive. Still get 32MPG on the highway travelling with 3 people, aircon and 70-80MPH.

i stand corrected.

 

[SamuraiJack]

Re: MPG?

Nope, the 5th is 1:1, we don't have an overdrive. Still get 32MPG on the highway travelling with 3 people, aircon and 70-80MPH.

I am having some similar mileage w/ the A/C on. I have made a couple of trips back and forth into town using the cruise control to maintain 65 to 70 in 5th gear and so far I am already at 210 miles @ 1/2 tank. So hopefully I'll hit 400 miles by the time the low fuel light kicks on. That's if I can continue to keep my right foot out of it.

 

[Akakubi]

LOL true! I easily made over 400 miles on one tank. The computer shows 480 miles is doable.