Which speed/gear is the most efficient in my car?

[OfficeLinebacker]

Originally Posted by Billy_BAD_Boy

You are not overtaking, are you?

LOL who would be overtake, poking around like that?

I must admit I do drive in a "spirited" manner on occasion but once I get on the highway into steady state driving, I'm the one being overtaken.

[Lazarus]

Originally Posted by PaleMelanesian

I heartily disagree. Go for the lowest rpm you can that will keep you rolling. It's lower than you think.

My 90's Japanese 1.6L 4-cylinder with similar gear ratios:
Runs steady speed just fine down to 25 in 5th gear (1000 rpm).
P&G driving, where I need a little more power, I limit 5th to 30 mph and above.

In your situation above, 35 in 4th or 43 in 5th, my answer would be 35 in 5th.

+1

[mcmancuso]

A metro Xfi can run at 15mph in 5th gear the Xfi cam and advanced timing lower the power curve significantly. (peak around 2K I think) A cam would be a good investment, as well as a 4-2-1(I think that's right) exhaust header to lower the power band but since you're looking to keep it stock...Can you advance the timing on this car, that should lower the power curve some and give better torque in the low end.

[PaleMelanesian]

Originally Posted by Billy_BAD_Boy

You are not overtaking, are you?

About the only time I overtake is when someone raced past me to a red light. I can time it and roll through on the green, when they're just starting from a dead stop.

You will get some shakes and shudders if you try a full-throttle acceleration at such low rpm. Just downshift before you try that.

[superchow]

Or you could try to use higher octane fuel. The ECU should recognise the increased knock resistance and adjust the timing. My 1.8L 07 Civic does just that. (And cost isn't a factor since I actually get more mpg per dollar that way. But it may take some experimenting.)

[mcmancuso]

99 probably does not have that kind of functionality, I'm pretty sure it was rather rare at that time to have an auto advance till it knocks setup in a small/inexpensive car.

[gone-ot]

...RULE-OF-THUMB: the highest gear at the lowest rpm that doesn't "lug" the engine.

[bgd73]

Originally Posted by IsaacCarlson

dang...get a low-end cam. That can give you a little more torque on the bottom end. It might be enough to let you use 5th at 35mph. You could also pick up a small industrial turbodiesel and put it in there. Those things make some torque!! I have been looking at some for my pickup and even at full load running against the governor, they only use 1-2 gal per hour. And we don't need to run them at full load and full rev going down the road. I did the math and I gould get 50+ mpg with a small industrial turbodiesel. The reason I saw industrial is because they are more efficient and are designed to WORK all day on a tank of fuel. My dad burns about 1.5 gal/hr in his bobcat.

that is a cool thought..
I saw a ford fiests with a 2cyl turbo diesel at a hot rod forum (yes an oxymoron) clever...

http://www.youtube.com/watch?v=FW_2oT4WiJg

if the car can take the torque, minimal throttle, and vibration that is the winning gear. it is very simple.
the little boxers are famous for this.. I take it to 1200 on a hill, let it rumble.
the diesels could do better, but as the cam wasmentioned, today they try to keep them higher strung like everything else wobbling.