Optimum gear to use for maximum MPG

[kambites]

5lab said:

I'm surprised it cancels out that low - I was under the impression it only went open-loop above ~90% throttle - but what do I know maybe its different on bikes? On Vauxhalls op-com can read the current state (ie open loop or not) but that's probably beyond the average driver

The Lotus seems to go open loop at well under 50% throttle. If I remember, I'll plot fuel mixture against throttle opening and RPM on the way home today and see exactly where it changes.

[conkerman]

If its in the NEDC = Closed loop.

Everywhere else - Open loop.

In reality, open loop everywhere of idle for most of us.

[cptsideways]

Generally speaking light load, very gentle acceleration only & gentle cruise speeds up to & including 70 ish mph on bigger engines usually gives you closed loop.

I think the 1.0 ecoboost engine has a very high load closed loop iirc even under boost conditions.

My old Toyota 2.5 1JZ-GTE Twin Turbo would cruise in closed loop at 140mph! effectively running at atm 0psi pressure (so off boost at the time) Quite impressive I always thought.

[Mr2Mike]

Vyse said:

Ever since Ive been driving Ive been told that to try and shift into the highest gear possible to get the best MPG. Can being in too high a gear at too low a speed in fact decrease MPG. For example being in 6th gear at 30mph in a highly strung NA car?

My Civic Type R is quite happy to pull 30mph in 6th on the flat. Having the engine run too slow for a given power output will increase fuel consumption however.

[Riknos]

Mr Will said:

It you want to use less fuel, stop worrying about which gear you are in and focus instead on the brakes. Every time you touch that pedal you are turning motion in to heat - motion that you burned valuable fuel to gain. You'll then have to burn more fuel to get back to the previous speed again.

Smooth flowing driving will save more fuel than anything else you can do.

This. The amount of people flying up to junctions / traffic lights / roundabouts and slamming the brakes of, surely loses massive mpg.

Smooth driving, smooth accelerating, smooth braking and using the gears, slow and look when approaching junctions and don't stop unless you have to, lift off when you need to slow down, rather than hitting the brakes, cruise along in as high gear as possible without labouring the engine, all good ways of driving. Should be the standard to be fair.

[GroundEffect]

The basic logic is if you aren't labouring the engine, be in the highest gear you can be. That's travelling the longest distance for the same amount of work.

[crox]

My company car is an insignia ecoflex, 2 litre diesel, 6 speed, eco tyres, start stop, etc etc.

At 70 it's right on the edge between 5th or 6th being most economical, 65-70, 5th is best. Just seams over geared!

In fact it have read that the car is average at best for towing, as 6th effectively is useless...