Author Topic: MPG for those interested  (Read 142606 times)

nowster

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Re: MPG for those interested
« Reply #225 on: December 29, 2021, 11:56:41 PM »
On every car I've owned, I can tell the difference in torque/HP between standard fuels and super - it will be increased further now with E5 and E10.

That might not hold true for the Mk4 Jazz due to its running the petrol engine in its power band.

sportse

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Re: MPG for those interested
« Reply #226 on: December 30, 2021, 06:07:57 AM »
On every car I've owned, I can tell the difference in torque/HP between standard fuels and super - it will be increased further now with E5 and E10.

That might not hold true for the Mk4 Jazz due to its running the petrol engine in its power band.
It should have an effect, but likely less than on a Toyota hybrid.

When cruising at high speed the petrol engine in the Jazz will be directly connected to the wheels, so any improvements in engine performance for torque/HP should be direct to the wheels.

When working solely as a generator, on super fuel, it will be giving maximum HP in generating.

Someone ran tests on a dyno with different fuels on a family car and found 3-4 HP increase with super fuel.

Jazzik

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Re: MPG for those interested
« Reply #227 on: December 30, 2021, 05:07:28 PM »
A fuel is a mixture of different hydrocarbons (including octane and heptane) that are present in different dosages. The ratio expressed in % between the content of octane and heptane is called the octane number.

According to the European directive, gasoline SP98 has an octane number of 98 and is composed of 98% octane and 2% heptane; gasoline SP95 has an octane number of 95 and is composed of 95% octane and 5% heptane.

And as for the engine?

The ratio of octane to heptane has an impact on the engine's auto-ignition mechanism. In practice, SP98 ignites at a higher temperature and pressure than SP95. This distinction is a result of how the different hydrocarbons respond to pressure. For example, octane will ignite less quickly than heptane. The lower the octane number, the greater the risk of spontaneous combustion at the time of compression in the engine cylinders.

Which petrol for which car?

Initially, it is recommended to use the fuel recommended by your car manufacturer. Anyone who thinks that a higher octane number leads to better performance is wrong.

If your engine is equipped to run on SP95 gasoline, like most regular cars, there's no point in filling up SP98. Certainly not in our Jazz with an ICE that runs with Atkinson cycle... You will pay more without getting more in return.

The proper functioning of your car depends on the compression level of your engine. This has an impact when the contact of the petrol with the air produces a spark. This explosion takes place at the right time with the right fuel, sensor checked.

And now that "damned" E10.

What is E10 petrol and bioethanol?
E10 fuel consists of a minimum of 90% petrol and a maximum of 10% bioethanol (so it can also be 94.5% petrol and 5.5% ethanol...). If the percentage of ethanol is below 5%, the gasoline is sold under the name E5. Ethanol, another word for alcohol, is often added to gasoline to reduce reliance on fossil fuels. Because the production and composition of E10 petrol is less bad for the environment, it is referred to as a sustainable petrol.

In principle, with a full tank of E10 fuel you will get a little less far than with a tank of regular E5 petrol. This is because E10 has a slightly lower energy density. A petrol engine consumes a maximum of about two percent more when E10 is refueled.

Two percent... Here in Poland we don't have E10 (yet), so we use E5. Our Jazz has so far a measured average consumption of 4.55 l/100 km = 63.5 mpg. So theoretically, consumption on E10 would have been 63.5 - 2% = 62.2 mpg.
Overtaking two, three, maybe four times quickly, a hundred miles more highway, more often headwind, less tailwind, etcetera etcetera probably gives more difference in consumption...

Oh... and maybe the air will also stay about 2% cleaner with E10...
« Last Edit: December 30, 2021, 05:11:07 PM by Jazzik »
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sportse

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Re: MPG for those interested
« Reply #228 on: December 30, 2021, 05:56:01 PM »
IIRC manufacturers all use the highest octane fuel available for their official fuel economy and performance figures - any tiny improvement is worth it to beat competitors.

I think they also tape up wing mirrors/etc just to get a tiny improvement. Another reason why we don't have spare wheels anymore, anything they can do to get a tiny increase in MPG/reduction in emissions.

Kremmen

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Re: MPG for those interested
« Reply #229 on: December 30, 2021, 06:01:48 PM »
Some manufacturers played with the software to detect when it was being tested to falsify emissions and possibly MPG figures.

They'll try anything.

Vertical windscreen wipers to reduce drag.
Let's be careful out there !

nowster

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Re: MPG for those interested
« Reply #230 on: December 30, 2021, 06:20:18 PM »
When cruising at high speed the petrol engine in the Jazz will be directly connected to the wheels, so any improvements in engine performance for torque/HP should be direct to the wheels.

Actually, it's only directly linked when it's in overdrive. If you floor it, the little gear will disappear from the display.

peteo48

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Re: MPG for those interested
« Reply #231 on: December 31, 2021, 01:36:21 PM »
With the recent spell of milder weather I am noticing EV mode kicking in much more largely because less power is needed to heat up the car. Heating the cabin will be my main drag on decent fuel consumption during winter months.

guest9814

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Re: MPG for those interested
« Reply #232 on: December 31, 2021, 07:00:50 PM »
When we run our car in town actualy no difference or small difference in  MPG when 98 RON used (said effects only more advanced timing with 98 RON in summer)
1 month ago I did trip with elevation from sea level to +477m fully loaded when used 98 RON and seen with car scanner that when motor generator have enough load car computer retarded ignition down to+7 degree (on flat road timing somewere on +35 degree) on that tank i did 974km from 35l of 98 RON gasoline - 2 trips 163km with speed 90km/h fully loaded with A/C set to 22 C with elevation to +477m then down -420m to Dead Sea and back  same route , rest is trips with 1 passenger - 2 trips 110km each with speed 90km/h and rest 448km  short trips 10-15km each in town (in town computer showed consumption 3.0l/100km average for 448 km ).
Now i switched back to 95 RON - in winter 98 RON not shows better MPG.
When outside temperature is low the 95 RON less prone to detonation.
But yes right fuel does better MPG
Should i get bad 95 RON gasoline that in reality in best case 89-90 RON i will get bad fuel economy, but if that real 95 RON it will be OK because our car should use 95 RON minimum.
Take look https://www.spritmonitor.de/en/detail/1195531.html this driver from Switherland uses 95 RON and getting excellent MPG.

sportse

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Re: MPG for those interested
« Reply #233 on: January 12, 2022, 12:05:12 PM »
After running my Jazz exclusively on Shell V Power 99RON for 7,000 miles I decided to try ordinary Shell 95RON E10 and switched over several fills ago…

On the motorway the drop in mpg has only been around 1mpg, whereas the cost is 10% more for the V Power.

There is a difference in performance though, not so much in total power but in the way it is delivered- V Power seems to have more pull at motorway speeds. It’s only the initial pull, actual performance seems similar.

Whereas ordinary 95 has more pull at lower speeds so is much better around town - there is less of an initial delay when pulling away/accelerating.

Ordinary 95 seems to actually be a better fuel for the Jazz, it appears to rev lower when under light/medium acceleration.

If I was driving around town a lot, I’d predict that 95 would actually get better mpg than 99!

Kremmen

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Re: MPG for those interested
« Reply #234 on: January 12, 2022, 12:23:29 PM »
I was considering topping up with Tesco 'premium' next time but based on your test I'll stick with the 95RON E10 jollop.
Let's be careful out there !

peteo48

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Re: MPG for those interested
« Reply #235 on: January 12, 2022, 02:10:11 PM »
Thinking along similar lines. I need to refuel so rarely that the extra cost per litre is not a deal breaker but if there is literally no point I'll probably stick with E10.

sportse

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Re: MPG for those interested
« Reply #236 on: January 12, 2022, 02:50:55 PM »
Thinking along similar lines. I need to refuel so rarely that the extra cost per litre is not a deal breaker but if there is literally no point I'll probably stick with E10.

It surprised me, in other cars I've owned there were benefits of using the super fuel - with the Jazz just being a generator engine usually it doesn't seem to make any real difference.

If anything, I'd say the Jazz runs slightly smoother on 95 instead of super. In my previous Yaris hybrid it was the other way round, but that had a gearbox and the petrol engine was driving the wheels through it in combination with the electric motors.

Expatman

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Re: MPG for those interested
« Reply #237 on: January 12, 2022, 03:08:08 PM »
I wonder in the longer term if the extra cleaning agents in Shell super petrol would benefit the engine? Also won't filling with E10 with 10%  hydroscopic ethanol increase the rate of water absorption into the fuel and is that likely to have long term corrosion risks for fuel lines etc?

Kremmen

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Re: MPG for those interested
« Reply #238 on: January 12, 2022, 03:10:46 PM »
I did a similar exercise in my first 8G Civic. I used Tesco Standard, BP Ultimate and Shell V Power. At that time I was doing a tank full a fortnight so I ran each for a month to reduce any hybrid mixes.

The results were almost identical with an average of only 1mpg difference and no noticeable performance gain.
Let's be careful out there !

sportse

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Re: MPG for those interested
« Reply #239 on: January 12, 2022, 09:26:03 PM »
I wonder in the longer term if the extra cleaning agents in Shell super petrol would benefit the engine? Also won't filling with E10 with 10%  hydroscopic ethanol increase the rate of water absorption into the fuel and is that likely to have long term corrosion risks for fuel lines etc?
Most fuels have cleaning agents added, it’s just that the super fuels have more.

The standard agents should be fine, as for E10 as it’s marked on a sticker in my fuel flap as approved I’m not worried - I tend to get through a tank or so every week so water absorption shouldn’t be an issue.

If the car was being left for a few months it might make a difference, but you could fill up with super fuel before leaving the car. V power is marked as ‘up to’ E5 but may actually be E0.

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