2000 rpm
 

my friend and i were talking about gear ratios, and some how he said about 2k rpm was the best rpm for mpg. my question was yeah on what size motor.
then he correted and said smaller motors nee high rpm to cruise at tha same hp. well to do 55 mph my 98 taco needs about 40hp.

that got me to thinking what mph are you guys at, at 2000rpm in top gear?

98 4x4 tacoma 2.7 5 speed manual. 59mph@2k rpm
09 4x4 tacoma 4.0 5 speed auto 67mph at 2k rpm
07 camry se 2.4 5 speed auto 63mph at 2k rpm.

if i remember correctly
09 silverado 4x4 5.3 4 speed auto 80 mph at 2k rpm.

my civic 1.5 vx 2k rpm I think is right around 60 mph, my old crx hf 2k rpm was around 68mph with the 1.5 engine that put out a peek of 58hp... it's really what it is tuned for, just replacing my civic exhaust made a difference, the old exhaust was larger around and that low end power came back as soon as I went with the stock small exhaust, mileage started to come back up as well even with the cold.

Hi,

IIRC, my xA is only going about 40mph in 5th gear at 2K RPM. To go 60mph, is ~3200 RPM... I need taller gears, and/or a final drive under 4:1.

I think my truck is at 58mph or close to. The car I think is 65mph or close to. I know the car runs under 2K at 60mph, and the truck is real close, might even be dead on. Very different motors, very different gearing. The truck runs out much faster.

2000 rrpm is just a rule of thumb. The rpm for best economy could vary a lot depending on engine design.

My car gets it's best at ~1600 rpm,

I've heard that best mileage is close to the peek torque, not sure if this true or not but if you look at the big chilton repair books they give torque for different engines and the range for civics is between 2,000 rpm for the crx hf's an up to 5000 rpm for some of the SI engines, so it so it does vary alot, you can't make blanket statments.

Not just engine design. Toss the same engine in a heavier car (or add three over weight adult passengers - say 250lbs each - to the current car) and the most efficient rpm will be significantly greater than 1600 rpm.

If i remember correctly:
1.1L Fiat Punto (1996 model), 5th gear at 2000rpm = about 40mph.
30 mph is about 1600rpm..

I don't claim to be a master of internal combustion engine wisdom, but coming from an expedition vehicle background the rule of thumb has always been to gear (axles) and/or shift (manual trans) so your most frequent travel speed coincides with the torque peak RPM of your engine. Fuel efficiency for expedition vehicles is important, not as much for financial reasons but because of the distance that may exist between fuel stations.

i'm also doing about 40 at 2krpm in fifth... it is disgusting. I'd rather be at 60. That's a big difference.