Clubjazz - Honda Jazz & HR-V Forums

Honda Jazz Forums => Honda Jazz Mk1 2002-2008 => Topic started by: Jocko on May 01, 2017, 07:25:56 AM

Title: Amazing mpg
Post by: Jocko on May 01, 2017, 07:25:56 AM
I topped up my tank today, after 404 miles of city, town, country and motorway driving (a good mix of each). My calculated mpg was 53.3. However, after filling up the tank at the top of the town, a gentle run home, through a quiet 40 mph section, saw my average mpg indicator reach 103.8 mpg. (This is an average, not an instantaneous value. Mk1 Jazz doesn’t do instantaneous.) This is a new record for me. 75 to 80 mpg is the norm reached on this run home. After a rather steep climb from the filling station it is mainly a gentle descent, with several flat sections, but it is interesting to see just what can be achieved in ideal conditions. Next time I go out, into the busy traffic and with a cold engine, it will soon be back to its normal 50-55 mpg.
Title: Re: Amazing mpg
Post by: JazzyJJ on May 01, 2017, 09:40:41 AM
Even 50-55 is very very good - wish I could achieve that. I can't get more than 45 and i drive in a very relaxed style town and a few miles motorway now and then - no racing.
Title: Re: Amazing mpg
Post by: guest6425 on May 01, 2017, 10:03:06 AM
103.8 mpg ????

Wind up?

what did you do, reset trip meter and freewheel down a long hill for a few miles?

I don't think that's possible.

Fill up your tank, reset avg mpg, drive as carefully as you like, when yellow low tank light comes on, post your Avg MPG along with how many miles covered

I'll give some examples from my 11 plate 1.4 EX (from tank brimmed to yellow low fuel light) Even on long pootling motorway journey I've only had 350 ish miles to the tank as a max.

48.1 - over 304 miles
47.5 - over 308 miles
45.5 - over 304 miles

You 'topped up' your tank after over 400 miles of mixed driving??
Sheet I need to get a mk1 Jazz, clearly I have the wrong version.

Any idiot can get a crazy mpg on a hill over a short distance, it doesn't make it especially accurate or truthful though.
Title: Re: Amazing mpg
Post by: d2d4j on May 01, 2017, 10:06:31 AM
Hi

I generally attain between 38 - 46 mpg from our si

I drive a lot with cruise control on, even at 30 mph and I'm not heavy footed. However, air conditioning is always on, so I guess this reduces the mpg. Sorry if I'm wrong on air conditioning.

Many thanks

John
Title: Re: Amazing mpg
Post by: guest6425 on May 01, 2017, 10:09:29 AM
They reckon about 5% for aircon, which in my case loses me around 2 mpg, not  so bad.
Title: Re: Amazing mpg
Post by: Jocko on May 01, 2017, 11:14:46 AM
103.8 mpg ????

Wind up?

what did you do, reset trip meter and freewheel down a long hill for a few miles?

I don't think that's possible.

Fill up your tank, reset avg mpg, drive as carefully as you like, when yellow low tank light comes on, post your Avg MPG along with how many miles covered

I'll give some examples from my 11 plate 1.4 EX (from tank brimmed to yellow low fuel light) Even on long pootling motorway journey I've only had 350 ish miles to the tank as a max.

48.1 - over 304 miles
47.5 - over 308 miles
45.5 - over 304 miles

You 'topped up' your tank after over 400 miles of mixed driving??
Sheet I need to get a mk1 Jazz, clearly I have the wrong version.

Any idiot can get a crazy mpg on a hill over a short distance, it doesn't make it especially accurate or truthful though.
I did say it was after a top up, a short mileage and a more or less gradual descent. What I started by saying was that after a 404 mile mixed traffic tank full, filling up when yellow light came on, I had a calculated mileage of 53.3 mpg. Since buying the car, last July, I have averaged 52 mpg - calculated - which I am thrilled with. Much better than the 29 mpg my Volvo S40 was averaging. I know full well that the indicator is just that. An indication that needs calculated figures to confirm.
Title: Re: Amazing mpg
Post by: VicW on May 01, 2017, 11:34:16 AM
However, air conditioning is always on, so I guess this reduces the mpg. Sorry if I'm wrong on air conditioning.

The aircon is there to be used for the benefits it gives, the little bit of increased fuel consumption is worth the advantages. My aircon is on all year round and my overall average fuel consumption is about 46mpg.
I am amazed at the number of modern cars including luxury cars, all with aircon, that are being driven with the windows open. The open windows increase the fuel consumption by at least as much as the aircon but you don't get the benefits.
Use the aircon and enjoy.

Vic.
Title: Re: Amazing mpg
Post by: Jem on May 01, 2017, 12:14:35 PM
I only ever manage about 44mpg which is mail city driving. On a longer run I might get 48. I think a lot of this is down to the tyres on the car. I only have cheapish kumho tyres on mine. I am sure if I went for a bit more expensive I could probably get better mpg.
Title: Re: Amazing mpg
Post by: Jocko on May 01, 2017, 01:26:00 PM
My Jazz is the bottom of the range, with nothing that uses any excess energy. No air con, no cruise control, no sun roof, skinny little steel wheels, nothing to use energy other than to propel the car forward. I always keep the windows closed as the car is at its slipperiest when all the windows/sun roof are closed.
My Volvo had air con, and I kept it on all year round, never opened the sunroof either. I also found that I got better mpg without the cruise control than with it. You would be approaching the top of a hill and the cruise control would change down (automatic) to maintain speed, whereas I would just let the speed drop off a smidgen, knowing I would pick it back up as I topped the crest.
Tyres can make a big difference to fuel economy. Modern wide wheel/tyre combinations use more fuel than narrow ones. You can also buy tyres specifically for low rolling resistance and in turn better fuel figures.
I go almost everywhere in 5th gear. I find that car will pull happily, on a flat road, from 22 - 25 mph in 5th. I use lower gears if traffic demands, but I get into 5th as quickly as possible and stay there as long as possible. I seldom ever exceed 60 mph. Every doubling in speed takes four times the energy and as cars are optimised for best open road fuel consumption around 56 mph it is not a bad speed to cruise at.
Title: Re: Amazing mpg
Post by: guest6436 on May 01, 2017, 11:31:06 PM
I constantly had 65-70mpg with 1.2Jazz and Good summer tyres in good weather driving at constant 85-90km/h in totally flat areas with barely any hills, Drop it to 70km/h and you were able to get 80mpg!

With 1.4Jazz and UK hills + winter tyres I currently got on the best I have ever had has been 55mpg over long drives.
I can get 100mpg+ with help of  hills+ city traffic as well :D Not that hard,just depends when you reset your counter ;) haha
Title: Re: Amazing mpg
Post by: Jocko on May 02, 2017, 06:43:36 AM
just depends when you reset your counter
And that says it all. I just happen to have that trip home from the filling station, where I have topped up and reset my trip counter.
Title: Re: Amazing mpg
Post by: peteo48 on May 02, 2017, 12:05:47 PM
I find with petrol cars the variation of mpg is greater than in diesels - or that's my experience anyway. I do a lot of short stuff and only occasional motorway use so I am relatively content with my overall mpg of 42 (measured - not computer reading which is 46). Over the 2 jazzes I've owned I have a record mpg of 56.2 and a low of 33.9.

I reckon if I was still doing my old 34 mile round trip commute I'd be at just under 50 which I regard as pretty good for a petrol.
Title: Re: Amazing mpg
Post by: Jocko on May 02, 2017, 01:31:13 PM
My works van (diesel) returns virtually the same mpg every day, irrespective of type of miles or the weather.
Title: Re: Amazing mpg
Post by: Everett on May 02, 2017, 03:58:36 PM
My works van (diesel) returns virtually the same mpg every day, irrespective of type of miles or the weather.

Damn that's pretty good. Mine is never that high lol.
Title: Re: Amazing mpg
Post by: guest6876 on May 18, 2017, 09:55:46 AM
I have had my 39,000 mile '06 1.4SE for about a month now and have covered 1000 miles which constitutes a 50 mile daily commute along A roads with quite a bit of stop start traffic, but I am still getting 58mpg average. I do try to drive it economically, short shifting etc. but I am well pleased with the return  ;D. In contrast my wife has a 64 plate Si with just over 10k on the clock and she drives it mainly around town with 3 kids (and a Multimac car seat which weighs a lot), and that is only achieving 38mpg, so I guess it is really down to a lot of variables such as driving style, distance of journeys, amount of people/luggage in the car etc.
Title: Re: Amazing mpg
Post by: MikeG1944 on May 19, 2017, 01:54:12 PM
I think you hit the nail on the head; driving style. I get good mpg even driving short journeys, but drive economically with slow acceleration and slow or little braking; whereas my wife does worse with a lot of acceleration and braking from fast speeds quickly at the last minute. They do reckon that you can save a lot of fuel with a careful driving style. :)
P.S. I've given up explaining this to the wife LOL!
Title: Re: Amazing mpg
Post by: Jocko on May 19, 2017, 02:51:16 PM
They say you waste fuel every time you brake, as you wasted the energy getting up to that speed in the first place. Rather a simplistic view, but worth keeping in mind. I tend to use gentle acceleration on down slopes then allow the speed to drop off on the uphill sections. Better that than going downhill on a trailing throttle then having to use wide throttle openings on the uphill bits.
Title: Re: Amazing mpg
Post by: MikeG1944 on May 19, 2017, 03:14:59 PM
I do think the breaking does waste energy, and hence fuel Jocko, as otherwise F1 cars wouldn't bother using it to store the energy when braking, albeit a small amount. You are basically fighting the engine going forward by braking unless you drop the revs right down first before pressing the brake pedal (opposite of what my wife does LOL).

I think the CVT system is excellent as it selects the 'right gear' (the correct position on the cones) for the amount of torque and speed needed in Drive mode, and I doubt all but the best drivers could match that as good with a manual box. Hence it's very good mpg figures. :)

Mike.
Title: Re: Amazing mpg
Post by: Jocko on May 19, 2017, 03:39:55 PM
F1 energy recovery system gathers a huge amount not a small amount. KERS (the old system) gave 80 bhp for 6 seconds. The new system gives 160 bhp, 120 bhp from braking and the rest from exhaust heat recovery.
I remember reading a book, many years ago, about the Ford GT40's at Le Mans. At the end of the Mulsanne Straight their brake discs went from -10ºC to 1000ºC, every lap!
Title: Re: Amazing mpg
Post by: MikeG1944 on May 19, 2017, 03:47:36 PM
F1 energy recovery system gathers a huge amount not a small amount. KERS (the old system) gave 80 bhp for 6 seconds. The new system gives 160 bhp, 120 bhp from braking and the rest from exhaust heat recovery.
I remember reading a book, many years ago, about the Ford GT40's at Le Mans. At the end of the Mulsanne Straight their brake discs went from -10ºC to 1000ºC, every lap!

Didn't know they gained that amount Jocko, surprising they don't use the heat from the brake disks to recover more (excuse me while I file a patent).

Mike.
Title: Re: Amazing mpg
Post by: culzean on May 19, 2017, 06:54:03 PM
They say you waste fuel every time you brake, as you wasted the energy getting up to that speed in the first place. Rather a simplistic view, but worth keeping in mind. I tend to use gentle acceleration on down slopes then allow the speed to drop off on the uphill sections. Better that than going downhill on a trailing throttle then having to use wide throttle openings on the uphill bits.

If not much traffic around I tend to coast downhill and then coast up the other side or on the flat until speed drops too much, then back into gear, that way the engine braking is not absorbing power and you get full benefit of gravity - some say it is illegal, but who is checking ???  Also engine braking cools the engine (cold air going in with no mixture to explode and keep it warm) and a cooled engine is not as efficient as a hot one.
Title: Re: Amazing mpg
Post by: Jocko on May 19, 2017, 07:07:43 PM
SAAB's used to have a freewheel, back in the days of the 96 and some 99's. Rover had a freewheel up until 1959. On the later P4's it was engaged and disengaged by a large handle on the dashboard, not unlike a water valve!
Title: Re: Amazing mpg
Post by: d2d4j on May 19, 2017, 08:22:03 PM
Hi

A little off topic sorry, but I was gifted a car ... wortberg knight tourer (sorry if I have misspelled) in the eighties. Had to collect from dock lands London

Think lada estate but worse

That car had 3 forward gears I think and freewheeling in all gears. If you were not used to it, it was frightening approaching roundabout, junctions etc. My favourite trick was to put it in first gear at 40mph (when not touching the accelerator) haha never forget that car

Many thanks

John
Title: Re: Amazing mpg
Post by: Jocko on May 19, 2017, 10:47:05 PM
Wartburg Knight. I remember them well. Three cylinder 2 stroke. Three coils, one for each cylinder. A novelty back then.