Petrol - I watch the pennies

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#2711135 22-May-2021 08:01

the other thing i could think of - is maybe 98 fuel burns with less carbon or maybe has more detergent?. direct injected engines suffer from carbon build up and i'm after a fuel that prevents carbon build up ...

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#2711227 22-May-2021 11:10

eracode:

You’re having a larf, right? Are you saying the Nissan March has a high performance motor? And the reason we see so many Nissan Marches and similar driving so slowly and gutlessly around the place is because they’re driven mostly by cautious little old ladies - who I’m sure are lovely people but a PITA to other drivers who have to follow them around the suburbs at 32 kph. Nothing to do with the incorrect fuel.

Any car made recently is a high performance motor. If the march was like an old morris then it would be way slower, that is when 91 was appropriate in small motors. The reason people go slow in them is you literally have to floor it to get all the power at any revs because of stupid mapping of the throttle. When you do that then they are actually fine around town on good fuel, if they have bad stuff they are still lacking.

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#2711287 22-May-2021 13:31

Batman:

the other thing i could think of - is maybe 98 fuel burns with less carbon or maybe has more detergent?. direct injected engines suffer from carbon build up and i'm after a fuel that prevents carbon build up ...

The amount of carbon in petroleum is fixed. It will either be converted into Carbon Monoxide, Carbon Dioxide or soot in your tailpipe during combustion (and possibly some trace exotics), or released back into the atmosphere as unburnt fuel.

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#2711332 22-May-2021 14:32

Batman:

the other thing i could think of - is maybe 98 fuel burns with less carbon or maybe has more detergent?. direct injected engines suffer from carbon build up and i'm after a fuel that prevents carbon build up ...

You'll generally find more detergent additives in 98 over a 95/96 or 91 product, which does help, but it's not the be all end all. I've always followed a simple guideline of "When in doubt, put in premium", and I know that while my car is "fine" on 91 since I started giving it 95, it's felt so much nicer under foot. For the record I drive a cheapy Honda Fit with the 1.3L engine - started giving it 95 minimum when I learnt it's factory compression is 10.8:1. I've installed a bluetooth ODB2 doodad recently and I'm in the process of actually working out where the best value for money is with my car and the way I drive. So far I've worked out I'm very slightly in the black putting in 95 after the 6cpl discount from Caltex or Z with my Airpoints card working out a simple $ per km based on kilometers per litre readout given by the engine computer. Not exactly accurate for anything truely scientific but enough for me working out the best place to spend my hard earned dollarydoos.

Anything with forced induction (Turbocharger, Supercharger etc) should run on the highest octane you can get your mits on but a minimum 95. just my 2c there.

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#2711566 22-May-2021 20:29

Batman:

i have never seen a car manual that says use 98 fuel ...

so why should someone put 98 fuel in their car?

I have had at least 3 vehicles that recommend 98RON or higher in the manual (although show step-down advice that 95 is OK, and 91 for short term usage if 95 or higher is unavailable), like here:

It's generally only going to be applicable to high-compression, higher-performance engines.

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#2711567 22-May-2021 21:09

Does the next line say in this case only use eco mode?

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#2711568 22-May-2021 21:13

Batman: Does the next line say in this case only use eco mode?

No, "moderate engine speeds and a light throttle." :)

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#2711614 23-May-2021 09:29

shk292:
Here's a strange one, the specs for a Kia car in Australia and other markets specify regular unleaded petrol, while in NZ specify "95 Octane or higher

Recommended fuel is based on NZ fuel standards and may differ from those in the Owner's Manual"

But regular in Aus is 91 Octane, the same as here. Why would a different grade be specified here to other markets? Is there something wrong with our petrol?

Nothing wrong with our petrol. Octane ratings are calculated differently in some markets. For example the same engine with identical specs sold here and the US will show a different preferred octane rating figure in the US owners manual compared to the owners manual here.

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#2711617 23-May-2021 09:40

The reason European cars generally require a higher octane rating than US and Australian cars is due to the emissions standards applied in Europe.

Europe currently applies Euro 6 standards whereas the US and Australia only apply/require Euro 5. It is much easier to achieve Euro 6 using 95 or higher hence newer European cars are no longer using 91 like US and Australian vehicles do.

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#2711642 23-May-2021 11:08

Technofreak:

Nothing wrong with our petrol. Octane ratings are calculated differently in some markets. For example the same engine with identical specs sold here and the US will show a different preferred octane rating figure in the US owners manual compared to the owners manual here.

Both NZ and Aust use the RON Scale.

USA uses AKI. Rough conversion guide:

AKI = RON

87 = 91
89 = 93
91 = 95
93 = 98

So the regular 87 AKI fuel available in the US as the same as our 91... Should note that cars that can run regular is a marketing point in the USA, and some buyers such as rental car companies insist on that attribute. As an example, ford kept the v6 (which could run regular fuel) as an option in the mustang for quite a while stateside, despite their 4 cylinder turbo engine being lighter, more powerful, and more efficient (but needing mid grade). Mustang convertibles are a fairly popular rental car in the USA.

Avgas uses the MON unit. 100LL has a minimum of 99.6 MON. Comparison 91 RON road fuel is about 85 MON. (yes the LL stands for Low Leaded - Avgas is still leaded despot wheat we know about the harm of TEL).

Technofreak: The reason European cars generally require a higher octane rating than US and Australian cars is due to the emissions standards applied in Europe.

Europe currently applies Euro 6 standards whereas the US and Australia only apply/require Euro 5. It is much easier to achieve Euro 6 using 95 or higher hence newer European cars are no longer using 91 like US and Australian vehicles do.

The bigger factor is that 91 RON is basically unavailable in Europe (making up less than 0.1% of fuel sales. I think it is banned in many locations, an where it is not, low production volumes make it more expensive than 95, so it is fairly pointless for most retailers to offer. As such the ability to run on cheaper 91 grade fuel is not a selling point for cars in Europe. So the automakers might as well optimize their offerings for higher grades.

In addition to the euro 6 stuff you mention, in Europe, large taxes are often applied based on emissions ratings for car's (g co2 / km). By recommending (and optimizing) for higher octane fuels the cars will get slightly better emissions ratings, and therefor have lower tax obligations for buyers.

Should note that many euro brands have a global presence, and often will have different powertain offerings for different markets. When we were in hawaii last our rental car was a turbocharged convertible VW Beetle. VW had set this car up such that regular 87 AKI was the recommended fuel.

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#2711700 23-May-2021 12:10

Scott3:

Avgas uses the MON unit. 100LL has a minimum of 99.6 MON. Comparison 91 RON road fuel is about 85 MON. (yes the LL stands for Low Leaded - Avgas is still leaded despot wheat we know about the harm of TEL).

Avgas is still leaded because to date no one has been able to produce a viable alternative without using TEL that meets the specs required of Avgas. Yes, motor spirit has been used very successfully in some aircraft engines, however it is not suitable for all uses. One of the problems with motor spirit is vaporisation.

While the problems with lead are acknowledged what hasn't been widely acknowledged is the problems that come with the the additives added to petrol to replace the TEL. Basically replacing one baddie with another.

The over all effects of the continued use of Avgas are miniscule as Avgas forms such a small part of the total petrol usage. The safety benefits of 100 LL Avgas certainly outweigh any benefits of using unleaded alternatives.

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#2711949 23-May-2021 23:55

Technofreak:

Avgas is still leaded because to date no one has been able to produce a viable alternative without using TEL that meets the specs required of Avgas. Yes, motor spirit has been used very successfully in some aircraft engines, however it is not suitable for all uses. One of the problems with motor spirit is vaporisation.

While the problems with lead are acknowledged what hasn't been widely acknowledged is the problems that come with the the additives added to petrol to replace the TEL. Basically replacing one baddie with another.

The over all effects of the continued use of Avgas are miniscule as Avgas forms such a small part of the total petrol usage. The safety benefits of 100 LL Avgas certainly outweigh any benefits of using unleaded alternatives.

You have absolutely hit the crux of the issue with your first sentence. It is not possible to get rid of the TEL, and maintain the same properties at a price point that is competitive with 100LL.

But the exact same 100LL properties aren't actually required for general aviation. As an example the entire range of the popular aircraft engine supplier rotax are approved to run E10, MOGAS and avgas...

The reality is that ongoing use TEL with it's well known impact on human health is not a viable solution. As such I think we need to give say 10 years notice to the General Avaitaion community, and then ban it outright.

Also the world is down to a single (legal) TEL supplier, so even ignoring the health impacts we should be looking to move away from this for security of supply reasons.

The General aviation community will need to pick from the raft of alternatives.

https://en.wikipedia.org/wiki/Avgas#New_unleaded_fuel_grades

Personally I think a fairly high octane, ethanol free MOGAS is the likely outcome. (Either 98Ron, or 100Ron like NPD sells in the sough island).

Some modern planes with rotax brand or similar engines will already be approved for this.

Some engines will require approval

Some will require modification (hardened valves, compression reducing pistons etc), then approval, and will take a hit on peak power.

Some engines will not be viable to modify (or will result in a power loss such that the aircraft no longer preforms as desired), these will need to be re-powered or retired. It is possible that high performance General aviation will become the domain of turbine powered aircraft rather than piston.

I disagree that there are inherent safety benefits that come from 100LL. It's just that basically all pistion avaition engines are approved for that fuel that is preventing change. I bet people made similar arguments 40 years ago with regards to automotive fuel.

I get that general aviation will lag behind motoring and marine fuels, but seriously we started the phase out of leaded road fuel in 1986, and banned it in 1996. It is now 2021, and General Aviation is persisting with this same fuel.

NZ's fuel tax policy actively encourages the aviation community to persist with AVGAS, rather than switch to MOGAS. - The latter attracts road user tax, no refunds are available for non commercial boating.

[for the benefit of those unfamiliar with this issue, only piston planes (generally smaller stuff, i.e. the four seater Cessna Skyhawk) burn AVGAS, which is basically high octane leaded petrol. Bigger stuff (i.e. the entire Air NZ fleet) is typically either jet or turboprop and burn Jet A1, which is basically Kerosene, closer to diesel than petrol.]

Batman

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#2711954 24-May-2021 07:03

how does higher RON decrease emission? thanks

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#2711988 24-May-2021 09:28

Batman:

how does higher RON decrease emission? thanks

It would only if the engine is designed for the higher rating. Higher compression ratio and a smaller engine for the same power output means more efficiency and therefore reduced emissions.

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#2712052 24-May-2021 10:19

richms:

eracode:

You’re having a larf, right? Are you saying the Nissan March has a high performance motor? And the reason we see so many Nissan Marches and similar driving so slowly and gutlessly around the place is because they’re driven mostly by cautious little old ladies - who I’m sure are lovely people but a PITA to other drivers who have to follow them around the suburbs at 32 kph. Nothing to do with the incorrect fuel.

Any car made recently is a high performance motor. If the march was like an old morris then it would be way slower, that is when 91 was appropriate in small motors. The reason people go slow in them is you literally have to floor it to get all the power at any revs because of stupid mapping of the throttle. When you do that then they are actually fine around town on good fuel, if they have bad stuff they are still lacking.

You should stick to your area of expertise (apparently the Nissan March) and stop making ridiculous blanket statements. The vast majority of cars in NZ are designed to run on 91 octane.

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