[Ankleface]

Hi there, I have a very small and light car with a tiny non-turbo 3-cyl DOHC indirect injection engine using throttle-by-wire and a 5-speed manual trans. I mainly use it for a daily short trip (not possible to combine together with other trips) in a small city with lots of traffic lights that are really poorly synchronized, on my route I often end up hitting all 5 lights on red over 75% percent of the time. There are also quite a few moderate hills, and unfortunately a steep climb to leave my neighborhood while the engine is still not warmed up. I use the air conditioning very sparingly, but it doesn't seem to affect the fuel consumption much either way.

I'm fairly experienced with the principles of efficient driving in small cars, and I used to easily get 10 MPG over the window sticker fuel economy on a slightly larger 4-cyl 5-speed manual that I used to drive in a different rural+city mixed driving route. But I'm extremely unimpressed with the consumption of my current car in my current environment, which is getting 10 - 12 MPG *less* than the manufacturer's rating. I run the highest practical tire pressure, I meticulously maintain the vehicle, and I'm pretty sure that it's not a mechanical problem because the consumption on longer trips meets or exceeds the window sticker rating.

The first culprit seems to be accelerating up the hill out of my neighborhood in 1st or 2nd gear before the engine is warmed up. At that stage I can feel that the engine is still running rich and hesitates more than it does when it's up to operating temperature, and by the time I reach the top of the hill the average fuel economy drops by ~0.5 MPG. I wonder if I should #1) let the engine idle a bit longer to warm up first in my driveway (the owner's manual recommends just 15 seconds of warmup) and/or #2) Go up the initial hill in 1st gear all the way or #3) Try to go up in 2nd as soon as as possible with my foot to the floor. (It's a moderate climate, so "cold" engine is just a relative term.)

And then when accelerating from stop lights, I'm trying to decide which is better: #1) Faster acceleration with higher RPMs for a shorter period of time to get out of the lower gears more quickly and possibly even skip shifting to reach 4th or 5th as soon as possible, or #2) Moderate acceleration around 2000 RPM with higher load in 2nd - 3rd usually foot-to-the-floor to reach cruising speed at 4th or 5th. I'm pretty sure that the #3) option of leisurely acceleration with lower load through all the gears until reaching 4th or 5th would use the most fuel. I'm concerned about the effects of "lugging" the engine, but it's often unavoidable because it has very low torque, and I never let it shake or struggle either. And I know that in theory if the throttle is wide open and dumping in lots of fuel that isn't getting fully combusted then it would be inefficient, but I don't think that a modern throttle-by-wire fuel injected system would do that even if I am foot-to-the-floor.

Thanks in advance for any suggestions and insight.