5th Gear or 6th

Smartiemnx · Dec 13, 2005

Have been reading through the thread on Economy, and seems there are many different opinions out there.....

Doing say 80 with cruise on in 6th, am I getting better economy than I would in 5th ??

Looking at the Computer read out suggests that I am getting better in 6th, but saying that as soon as start going up a hill it looks like its using a hell of a lot more, than if I was going up the same hill in 5th

I'm confused, can anyone help ??

craig-pd130 · Dec 13, 2005

At 80-ish there's actually not that much difference between cruising in 5th or 6th .... sometimes I'll do a long m-way trip and stay in 5th at 85-ish to let the engine rev a bit and clear it out, and I still get 52 - 53 mpg.

The real difference is, it's noisier in 5th .... although it's also more fun when you floor it to p*ss off a tailgater

sssstew · Dec 13, 2005

yes your probably labouring the engine a little too much for it to give best economy when going up a hill in 6th and trying to maintain a pace so a drop to 5th would help.

muddyboots · Dec 13, 2005

IMHO 6th is fine when at that kind of speed; the engines turning fast enough that the turbo's spooled up and quite responsive.

At lower speeds, if the turbo's starting to drop off boost and you need a heavier foot to pick up speed again, a lower gear would be better.
When off boost and trying to accelerate, the PDs overfuel to try and help spool the turbo up; so if you're constantly dropping off boost because of being in a high gear and then flooring it to pick up speed again, it is usually more economical to drop a gear.

6th on the Ibiza PD130 Sports is very high, I rarely use it below 60mph, lower gears give better economy.
And on the motorway, in 6th, I find the mpg seems to peak at around 80mph - which is roughly at the engine speed where peak torque is developed.

Smartiemnx · Dec 13, 2005

muddyboots said:
IMHO 6th is fine when at that kind of speed; the engines turning fast enough that the turbo's spooled up and quite responsive.

At lower speeds, if the turbo's starting to drop off boost and you need a heavier foot to pick up speed again, a lower gear would be better.
When off boost and trying to accelerate, the PDs overfuel to try and help spool the turbo up; so if you're constantly dropping off boost because of being in a high gear and then flooring it to pick up speed again, it is usually more economical to drop a gear.

6th on the Ibiza PD130 Sports is very high, I rarely use it below 60mph, lower gears give better economy.
And on the motorway, in 6th, I find the mpg seems to peak at around 80mph - which is roughly at the engine speed where peak torque is developed.

cool, this is kinda what i was thinking, i've come into the 150 from a 110 , so its just a bit of getting used to i think....

Cheers.....

craig-pd130 · Dec 13, 2005

I find the "sweet spot" for best economy and a quick / safe cruising speed is 2,600rpm / 82mph in 6th (Passat PD130) but that's probably also because of the aerodynamics of the car ..... this gives a typical instant mpg reading of about 60-65mpg.

It isn't much more economical below this figure and above 2,800 rpm / 90mph the mpg starts to drop off quite sharply.

AndyVTR · Dec 13, 2005

Still not convinced so I stick to indicated 70mph in 6th. I return 55's regularly. Might try an indicated 80 run one week maybe.

dmjw01 · Dec 13, 2005

My gut feeling is that at motorway speeds the aerodynamic (in)efficiency of the car becomes more important than the fuel efficiency of the engine. I doubt you'll see a great deal of difference - so just stick it in 6th gear and enjoy the quieter sound. At 70, my TDI FR Ibiza is doing about 2100 rpm and it certainly doesn't feel like the engine is labouring.

sssstew · Dec 13, 2005

agreed, at 2100 the engine certainly wont be labouring, will be nicely on boost.

AndyVTR · Dec 13, 2005

Mine is just under 2k at 67mph. We done this before?

KevinG · Dec 13, 2005

Anything around 70 mph seems to return better mpg in 5th gear than the same speed in 6th - which is quite tall and becomes very sensitive to the smallest incline it seems.

AndyVTR · Dec 14, 2005

Even on a motorway with cruise? Might try it next week then. How are you seeing that Kevin? Just on the instant read out? I tried 67 in 6th and 75 in 6th and it was better at 67mph. If it's over a full tank i might be more convinced as just doing 40mile or say can vary too much on how you drive and if you get some clown on your arse.

KevinG · Dec 14, 2005

Hello Andy, yes this is on a motorway, but no cruise.

I guess I'm talking mainly about the 65-70mph range. And yes, its the instant readout so maybe not all that accurate.....

At 80, I find 6th the best.

Weird because a friend who has a Vauxhall Signum (?) 1.9 TDi and his sweet spot is ~60mph in 6th?

Maybe its me.

and yes clowns a-plenty (the m4 in rush hour)

muddyboots · Dec 14, 2005

Of course it all depends on the engine in question, at what rpm peak torque/efficiency is developed, and gear ratios - so it will vary quite a bit between different car models.

sssstew · Dec 15, 2005

AndyVTR said:
Even on a motorway with cruise? Might try it next week then. How are you seeing that Kevin? Just on the instant read out? I tried 67 in 6th and 75 in 6th and it was better at 67mph. If it's over a full tank i might be more convinced as just doing 40mile or say can vary too much on how you drive and if you get some clown on your arse.

andy dont forget you need to try it with inclines, thats when the effect in fuel economy would be noticed. Working harder in 6th will use more fuel going up hills that being in 5th with a few more revs and less labouring.

Bunglebonce · Dec 15, 2005

I change down when the rev counter just goes under 2k on busy / hilly bits of motorway. That way your not labouring the engine if you know your gonna hit a hill or are going to have to slow up and accelerate again.

That said, if you're on a real flat piece of road and you can safely say that you will be able to waft along for a while without the need to accelerate further, then the 6th will give you greater fuel economy e.g. you can do about 60mph in 6th @1200 rpm and it wont labour the engine so long as you dont need to apply more throttle to overcome a hill or accelerate.

But it gets a bit boring after about half a mile so you drop it into an appropriate gear and floor it

sssstew · Dec 15, 2005

yes spot on bungle.

keithrann · Dec 15, 2005

God i feel like a speed demon! I usually sit about 90-100 on motorways when its relatively clear! Think the current mpg reading shows about 25mpg ish!

sssstew · Dec 15, 2005

that speeds not for me, i tend to think the pigs will pull you at 90-100, but they arent gonna bother about 80 or so.

muddyboots · Dec 15, 2005

sssstew said:
that speeds not for me, i tend to think the pigs will pull you at 90-100, but they arent gonna bother about 80 or so.

Snap.

Also, we've been talking about economy at motorway-type speeds. The ultimate economy will be had on roads where you are typically sat in a steady convoy doing 40-50mph on level roads, where your foot is hardly touching the throttle.
That's where you start getting into 60-70+mpg territory

5th Gear or 6th

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