correct gear for fuel efficiency

sevenhills

neilmcl wrote: »

As per my post, the ECU is programmed to know exactly what the correct power band is for that engine and will inform you which gear you need to be in at any one time to achieve this.

That maybe the case, but the computer does not know of the conditions of the road ahead, or whether you are likely to be slowing down in 5/10/60 seconds.

forgotmyname

LindaJoan wrote: »

Hi. This is one of your MSE tips (below) but is the exact opposite to what I was told on a recent speed driving course- that this advice is out of date as its based on old cars and is a myth because all new cars are much more fuel efficient at lower gears. The advice was- match the gear to the speed for fuel efficiency ie. 20 mph for 2nd gear,30 mph for 3rd gear,40mph for 4th etc so what is the actual evidence for the fuel efficiency with each type of driving? Also the course advice was designed to reduce speeding and make roads safer.
MSE TIP-Change up a gear sooner. Always drive in the highest gear possible without labouring the engine. So change up much earlier than feels natural !!!8211; it will take some pace out of your acceleration, but as that's our first tip it isn't a bad thing. If you have a fuel efficiency display, you'll be surprised how immediate an impact this has.

Are you the MSE spokeman / woman then?

Why are you spouting LIES? Its not the 1960's you know. Did you realise long stroke engines are a dying breed??

I tried your method and my average MPG went DOWN by 23%. Where do i send my bill for fuel you cost me?

Jackmydad

I run my car on fuel extracted from spam.
It will do up to 120mph in first gear, so I now never need to change gear, and remarkably I get around 60 mpt. (That's "miles per tin" incidentally)
The residue is quite nice on sandwiches with tomato and mustard.

almillar

Hmm. Well there's not 1 speed for 1 gear. There are different cars with different gearboxes and engines and there are also things like hills, so the only firm rule is, be flexible.
A high gear without straining the engine is a good guide, but with this you are left open to the car being allowed to run away - you've got less control over your speed - going down a gear might help control speed better with better throttle control at higher revs.
And auto gearboxes, even DSG ones, are dumb!

System

I do a 28 mile each way commute almost all on rural main single carriageway A road at NSL with some hills to go over. Done it at cruise control maintaining the speed limit (joys of commuting at 3am in a rural county) using 5th gear at 60MPH and 6th gear at 60MPH and noticed NO difference over a week in the average fuel reading.

OTOH at work we've got some new lorries to replace the 64 plate ones we have. They run different final drive ratios, change gear earlier and drive how you suggest. Despite being 480BHP instead of 460BHP ones they replaced they're returning around 10% higher MPG. HOWEVER because they change gear as the OP suggests they're slower on acceleration and climbing hills and the 4 year old 460BHP ones despite having 700,000km more on the clock go flying past them up hills and setting off from a standstill. The newer ones which drive as you are suggesting basically achieve the fuel saving by accelerating slower and I reckon if you were to follow one with the old ones and match its speed you'd get the same fuel economy even though the engine is running faster as it'll have less load on it.

reeac

Lorries that fly up hills? I wish that the ones that I encounter could do that.

unforeseen

sevenhills wrote: »

That maybe the case, but the computer does not know of the conditions of the road ahead, or whether you are likely to be slowing down in 5/10/60 seconds.

I don't think there is any programming for my change indicator. If the revs go over 2000 and you are not in 6th then it tells you to change. I ignore it because I've found that 2300 seems to be the optimum for MPG and the engine sounding happy.

MataNui

Every modern auto i have driven tends to select higher gears and stay in them longer before down shifting. Since they would program the gearbox for max efficiency to pass the strict emissions tests i would guess higher gear (providing not laboring the engine) is going to be more fuel efficient.

loskie

My Honda CRV 2.2 diesel manual seems perfectly happy at 65 mph in 6th gear however the average mpg and instantaneous MPG display suggest that 5th is far more efficient.

peter_the_piper

As they say that the most efficient speed is about 56mph then driving at the rpm for 56mph in top gear, in the other gears, would be most fuel saving. My Picanto tells me when to change, not that I listen, but I do have the current mpg showing on the speedo.