Sweet spot cruising speed

[synergist]

Results can vary hugely for me depending on even whether it's a 1% or 3% gradient, but doing motorway cruising all week last week, I found 50-60 mph in sixth gear (Fiesta ST2, EcoBoost 1.6 litre) was giving me between 48 and 60 mpg which is around the 2000 rpm mark. If you keep throttle under about 45% input, the turbo doesn't spool (which knocks you down to 28 mph straight away).

Going at 70, mpg hovers around 35. 80 mph, mpg only decreases very slightly to between 28-32.

Even gentle pulse and glide on straights yields big MPG increases as the engine shuts off the injectors. I wish I could run on just two cylinders for motorway cruising, I'd get amazing MPG with this engine.

[Draigflag]

They seem like huge differences in economy, for small changes in RPM, but petrol turbos can be like that I guess, unlike diesels which are more consistent. Yea a lot of newer car have cylinder deactivation now so they only pump fuel into half the engine. VW uses this on their eco models.

[JanGeo]

Ahhhhh I bet you don't have ethanol added to your gas like we do in the USA! I really wonder how much better my mileage would be on straight gasoline.

[Draigflag]

Probably not, fuel here is very different, it has more lubricants and additives in aswell and far less sulphur too, which is why oil change intervals here can be up to 30,000 miles! I've been told the US is switching to low sulphur fuel soon, so hopefully you guys will be able to do far more miles between oil changes and help save oil.

[litesong]

Originally Posted by synergist

I wish I could run on just two cylinders for motorway cruising, I'd get amazing MPG with this engine.

That's why they made the 3-cylinder turbo. Ya save one cylinder functioning at ALL times.

[spartybrutus]

I have a couple of speeds at which my Sonata 1.6t ECO 7sp DCT auto tranny up-shifts (37mph/6th and 48mph/7th). This drops RPMs down to 1300-1400. So, ~37mph or ~48mph are ideal cruising speeds for this vehicle. In reality though, I'm cruising at 55-60mph posted limits for most of the daily drive. This is yielding 38-41mpg tanks for a full size sedan.

[Draigflag]

Well I just completed a 300 mile trip from North Wales to South, and back again. About 10% was motorway, the rest was rural single carriage way roads, very hilly and bendy. The speed on these roads varied from 50 to 60 Mph but there was a lot of traffic being a Bank Holiday. On the motorway I stuck the cruise on at 65 Mph, the revs are around 2000 at this speed. I managed an impressive 71.8 MPG for the entire journey (about 60 US MPG) which considering I was driving normally for most of the journey, going up hills, overtaking etc, I'm very happy with the results.

[FusionConfusion]

That's unreal mpg's...70!? Holy ship! Safe to guess it's a little diesel? (didn't look at your Fuelly Page...could do that I suppose) I've got a 1.8 Sonic (not sure what they're called out there) 5 spd and I can't get close to 50. 40 is more like it... my lifetime avg is around 7.3l/100 (39 Imp mpg). Which sucks. That's impressive numbers though.

[Draigflag]

Yes it's a small diesel. 72 MPG is 60 mpg in the Us. We don't get the sonic I don't think, but it looks similar to a Chevy Aveo. Your MPG for the Sonic is showing as about 36 MPG here.

[trollbait]

The Sonic is still called Aveo in most of the world, and Barina(I think) in Australia.