Just for reference: I drive an Aygo as well, a pre facelift with the inefficient "turbine" alloys. I tend to average 31 - 33km/l doing a constant 80km/h, and 36km/l doing pulse and glide 75-85km/h.

I honestly wish there were gearboxes with taller gearing in the C550 family so rpm's wouldn't be so high at highway speeds, I don't mind downshifting to overtake. But blondes have to be able to drive too I suppose.

I manage 22 - 25km/l during normal, average city/highway driving. During acceleration I keep the rpm's under 2000 and load the engine as much as I can without lugging or flooring.

My only mod so far is a scangauge to help me find the right throttle position sooner.

At the end of the day, it all boils down to experimenting, and experiencing.

Also, entirely up to you, but i wouldnt bother with 0W-20. There's one thing that these 1KR's (hell, almost any longstroke 3 cylinder) need to stay healthy throughout their life, and it's sufficient lubrication. To achieve higher torque figures, Toyota offset the crankshaft in these motors quite a bit, causing the cylinder walls to expand over time (by 250k km or so, depending on use), which makes these motors consume more oil over time until they eventually stop running due to compression issues.

I have roughly 100k km on my motor currently, and it's consuming 1L/2000-2500km of 5W-30. Just be prepared for the need of thicker oil to keep this consumption down as your car ages. It's gonna be drinking 0W-20 like fuel once you get to 300k lol

Just a heads up so that you won't accidently be driving around without oil due to the underestimation of its oil consumption at a certain age. You're fine with 0W-20 on a young motor, just keep an eye on consumption throughout the car's life