Better off in a lower gear? (city cruising)

[Kodak]

This tank is looking pretty lousy so far. I know the gas gauge can't be trusted for precise measurement, but I have a pretty good idea of what it looks like on a good tank.

I've been using 4th gear for city speeds of 30 mph or slightly above (1500 rpm or just a bit less for my gear ratio). Feels low on power, but smooth. The 2.9L 4cyl does not like the really low rpms that some drivers on here seem to utilize in their vehicles.

May it actually be more efficient to use 3rd gear, which would land me a bit shy of 2k rpm?

The shift indicator light usually goes on in the low 30's when I'm in 3rd and babying the throttle, and higher gears just make sense for FE...but my gas gauge seems to disagree.

I know the new route I've been taking (shorter, slower, a few more lights) may be at play here, but my goal is to keep above 23 mpg.

Any tips on gear selection?

[nemo]

That planed ScanGauge would give you your gallons per hour using both scenarios.

[jakobnev]

Any tips on gear selection?

Neutral?

[Fr3AkAzOiD]

1500 rpms may be a bit low for peak fuel efficiency.

I have found that there are times where it is better to drive 5 mph faster to effectivly use that fourth gear then stay at the slower speed and use third gear but have much higher rpms.

[euromodder]

Originally Posted by Kodak

I've been using 4th gear for city speeds of 30 mph or slightly above (1500 rpm or just a bit less for my gear ratio). Feels low on power, but smooth. The 2.9L 4cyl does not like the really low rpms that some drivers on here seem to utilize in their vehicles.

A 2.9L should be able to pull it off though.

My 1.6L Diesel didn't like the low rpms until some hidden defects were sorted.
Now it will pull it off, as long as there's no upward slope.

May it actually be more efficient to use 3rd gear, which would land me a bit shy of 2k rpm?

Or run a wee bit faster in 4th.

Try some different approaches and see what works best on a given route.

[Kodak]

Originally Posted by nemo

That planed ScanGauge would give you your gallons per hour using both scenarios.

Part of my brain is saying: get it; it'll answer so many efficiency questions. The other side is saying: You just finally got over you tachometer obsession. Keep your eyes on the road.

Thanks for all the suggestions so far.

[JRMichler]

I have been in 5th gear as slow as 20 MPH. Acceleration is negligible, so driving with anticipation is absolutely required. A lot of anticipation. Scangauge says that 5th gets better MPG than 4th at these speeds.

It shakes and I don't want to go over about 10 lbs MAP, but it will pull on a level road or even a very slight upgrade. At that speed the alternator is still putting out current, but not enough to keep the battery fully charged.

Ultragauge is less than half the price of a Scangauge. Both give instantaneous MPG and/or fuel flow.

[Kodak]

Wow, 20 is low. What rpm is that?

The gauge looked low, but my fill today resulted in 23.38, which is about right for this kind of driving.

[JRMichler]

I dunno exactly, about 700 RPM.

[Kodak]

I guess my confusion is not understanding the fine line between lugging and low, but acceptable, engine speed.

I understand that throttle position plays a major role here, in that a speed of X in OD may be fine with light throttle, but lugging with say 20% throttle.

However, I can't seem to find the spot where I say 'okay, this is about the low end of my vehicle's threshold for level terrain.'