Super Unleaded Anyone?

[Mikeyb999]

Just wondering - does anyone use super unleaded?

I've not tried but was wondering if there might be any difference / advantage

[soramad]

Yes, I for one use super unleaded , mainly because I drive a V8 Soarer which is supposed to run on 100 ron petrol , super unleaded is usually rated at 97 ron but when I want that little bit extra I also use a petrol addative which is supposed to add an extra 2 ron , I can feel the difference in the initial acceleration and when I kick down so to me it works!

[steve2006]

I put the occasional half tank in, haven't noticed any benefits just the increased price of the stuff.

[scudney]

Yes I always use momentum 99 in mine,even introduced a friend who owns a golf v5 to it and he says it quieter and runs smoother.

[rayaans]

On older cars it makes a big difference. modern cars really don't care at all. You'd get maybe 1-2mpg difference in MPG but the stuff costs more and pretty much cancels out. I only use it about once every 3 months for the additives.

I used Tesco Momentum 99 once and I dont know if its just low grade fuel or what but it feels no different to BP standard unleaded. BP Ultimate is distinctively better than the standard though. Tesco's diesel sucks, makes the Merc shiver at 2k rpm

You have to remember that Lexus are primarily for the US market who have worse fuel than us. They recommend 87 octane fuel or above which is worse than our standard unleaded

[ColinBarber]

US fuel is measured in a different way to the UK so you cannot directly compare.

[rayaans]

US fuel is measured in a different way to the UK so you cannot directly compare.

Yes but generally, anything under 90 octane is worse than our standard unleaded.

[200h]

i have tried super unleaded from shell and milage wise no difference at all,to be honest th ct isnt fussy what you put in,

at the moment our shell station has closed for a 16 week refurb so i have used sainsbury's ,and milage wise no different

once shell reopens i will go back to as i feel it has better cleaning agents in it ,but right now i am happy.

[Mikeyb999]

Don't think I'll bother then. It used to make a difference in my smart roadster - ran smoother and better MPG, but not really noticed the difference in anything else I've run. Sounds like it wont make any difference to the CT

[Wass]

I thought that most modern cars were actually programmed to run maximum advance for whatever fuel was in the system and a sensor in the exhaust system told the ECU whether to retard the ignition or not for lower and higher octanes. However, i am not really sure how this system works with the Atkinson cycle rather than the Otto cycle.

[ColinBarber]

Toyota engines will make use of the extra performance in the fuel but it can take some time to adjust. You will see a difference, in my experience however the improvement is always less than the additional cost so I don't bother. It also seems less beneficial with a hybrid, I guess being the engine is running less.

[adnewton]

It won't make much difference with engines that run Atkinson cycle. They are designed to run efficiently with shorter piston strokes. Using anything over 95 RON is just waiting your money.

Why buy an hybrid if you want performance? Your driving style will benefit the mpg more than super.

[Silversalmon]

Hi guys, I'm interested in this debate as well, my previous Lexus, an IS300 defintely appreciated Shell Champagne and on a long run it was definitely worth the extra cost as mpg was definitely impoved. Around town it didnt matter as it just drank like George Best. Had the CT for a month and have only run it on 98 Ron Shell Champagne. Im getting 53 on average, over twice as good as the old car as a matter. Telegraph did a good article, http://www.telegraph.co.uk/cars/advice/is-supermarket-fuel-ok/ I always rate Honest John.

Great forum, had years of great advice from the old IS forum.

PS, what is an Atkins cycle engine?

[ColinBarber]

Atkinson cycle engines operate in a slightly different way to conventional 'otto' engines. They are more efficient but don't produce as much power and therefore aren't typically used for standard petrol engine vehicles. Hybrids use these engines to help boost overall economy with extra power delivered by electric motors and the CVT transmission allowing for the engine to operate at the most efficient rpm.

Some newer engines are able to alter cam and valve timing to effectively switch between Otto and Atkinson depending whether power or economy is currently needed. The 2.0 litre turbo engine in the NX200t is one example of this.

[Silversalmon]

That's about the best description I've read about these engines, many thanks, everyday is truly a school day!

Ed

[darrude]

My understanding (and I could be wrong!) is that there is no Calorific difference in the fuels, only a the higher Ron Fuel having more resistance to detonation. Using higher ron offers performance gains by allowing a leaning fuel to air ratio.

Can modern ECU's map for this. I remember reading a scientific study about 8 years ago (I think it was a Golf as the test car), and it showed no performance or economy benefits of the 2 fuels.

ColinBarber Can you confirm where you got your info from for the toyota engines. Surely the fact that it is a hybrid wouldn't make a difference as it would be to do with the amount of fuel used to power expelled?

[rayaans]

It won't make much difference with engines that run Atkinson cycle. They are designed to run efficiently with shorter piston strokes. Using anything over 95 RON is just waiting your money.

Why buy an hybrid if you want performance? Your driving style will benefit the mpg more than super.

That's not strictly true. The additives in the super unleaded fuels are much better for hybrid cars, especially ones with direct injection.

The additives clean the carbon deposits completely if used for around 5-7k miles which builds up on short trips

[Spacewagon52]

Very interesting - I try not to buy Shell fuel - On more than one occasion I have filled up with Shell and have had running problems - lack of power and acceleration. I tend to try and avoid Shell stations whenever possible. Just a personal preference from a bad experience.

[adnewton]

If you're prepared to pay the extra for very little return, then go for it. I certainly won't be.

[200h]

when i had a mercedes A class that i ran shell super unleaded on i used to see an extra 45 miles range from a tank full so it was worth paying the extra,i then changed to a ct and i didnt notice any difference between standard and super ,to be honest if i had to use super market petrol in desperation i didn't see any difference in the mpg i returned per gallon,so i just use standard shell petrol.

[Wass]

Put some in the tank by mistake. Drew the conclusion as follows:

Gain subtract Extra cost= Deficit

conclusion:Not worth the bother.

Additives provided (allegedly) by the more expensive fuel; benefits only likely to be revealed towards the end of the vehicles life span. Car is likely to be in somebody else's possession by then.

[ColinBarber]

My understanding (and I could be wrong!) is that there is no Calorific difference in the fuels, only a the higher Ron Fuel having more resistance to detonation. Using higher ron offers performance gains by allowing a leaning fuel to air ratio.

Can modern ECU's map for this. I remember reading a scientific study about 8 years ago (I think it was a Golf as the test car), and it showed no performance or economy benefits of the 2 fuels.

ColinBarber Can you confirm where you got your info from for the toyota engines. Surely the fact that it is a hybrid wouldn't make a difference as it would be to do with the amount of fuel used to power expelled?

Correct there is no difference in actual energy however the detonation performance is the key to the difference. With a higher RON fuel the ECU can use a more advanced timing, extracting more energy from the fuel.

The mpg attained from a standard petrol engined vehicle is 100% to do with the burning of fuel whilst the engine is running. On a hybrid a percentage of that mpg comes from shutting off the engine during deceleration or when stationary and an even smaller percentage from energy recovery. Therefore if you improve engine efficiency the overall percentage improvement on a hybrid will be less than with a standard petrol engine.

The hybrid engines are also typically running an Atkinson cycle which don't respond to higher octane fuel with the same benefit as an Otto engine.

[Wass]

My understanding (and I could be wrong!) is that there is no Calorific difference in the fuels, only a the higher Ron Fuel having more resistance to detonation. Using higher ron offers performance gains by allowing a leaning fuel to air ratio.

Can modern ECU's map for this. I remember reading a scientific study about 8 years ago (I think it was a Golf as the test car), and it showed no performance or economy benefits of the 2 fuels.

ColinBarber Can you confirm where you got your info from for the toyota engines. Surely the fact that it is a hybrid wouldn't make a difference as it would be to do with the amount of fuel used to power expelled?

Correct there is no difference in actual energy however the detonation performance is the key to the difference. With a higher RON fuel the ECU can use a more advanced timing, extracting more energy from the fuel.

The mpg attained from a standard petrol engined vehicle is 100% to do with the burning of fuel whilst the engine is running. On a hybrid a percentage of that mpg comes from shutting off the engine during deceleration or when stationary and an even smaller percentage from energy recovery. Therefore if you improve engine efficiency the overall percentage improvement on a hybrid will be less than with a standard petrol engine.

The hybrid engines are also typically running an Atkinson cycle which don't respond to higher octane fuel with the same benefit as an Otto engine.

Well said Colin

[rayaans]

Although with the new Lexus direct-injection engines, you're better off using the Super Unleaded for the additives. They claim their port injection helps to clean the deposits but who knows?

[ColinBarber]

There may be other benefits to using a more expensive fuel other than mpg/power gains, for example better additives to maintain your mpg.

Regarding port cleaning I'm not sure this is a big issue. Carbon build-up on inlet valves can be an issue for direct injection engines but no fuel additive can correct that as the fuel doesn't touch the inlet valves, which is the reason for the problem in the first place. This certainly isn't an issue for the CT200h as it isn't a direct injection engine.

CT200h, RX450h, NX300h aren't direct injection, the IS300h, GS300h, and GS450h are.