Do fuel brands/grades really matter?

[niteblade]

Hi guys!

Have a silly question that's been bugging me because everybody tells me contradicting answers.

Do the different brands of fuel actually have much impact on your engine? One example is Caltex Techron which claims to clean your engine. Or V-power which is "superior" fuel

Also is pumping Ron92 bad for your bike in the long run as compared to premium fuel such as 98?

Any technical experts care to share their views?

[Neosophist]

It depends on the vehicle with regards to pump number.

Generally though.

All modern (with the last 25 years) burn mainly unleaded and they burn very clean, not like 70 years ago when taking the engine apart to decoke (clean the crap out it) was part of the service schedule.

A higher pump number (US uses different scale to Europe) but same priciple applies here.

The higher the number, the more you can compress the fuel / air mix in the engine before it goes boom by itself.

Now, if you have a highly tuned tubod engine running at high pressures then you need a fuel that wont ignite before the spark plugs ignite it, this is where you high numbered fuels are needed, like the highly strung out turbod Japanese impreza etc.

Some very modern cars can also alter the timing to produce more power based on fuel (this is only really within the last 5 years)

The NC30 series of bikes are specced to use 91 octane unleaded. (87 PON) if you live in the US.

collectivly hundreds of thousands of miles between bikes using just that have producd no issues. The engines dont run dirty enough to require detergent anymore.

A dirty engine is most likely due to bad oil / conatimation etc which a bit of cleaner wont fix.

Which!? (uk test magazine) and many other places have done research and showed that unless you car can utalise the fuel, using `super` fuels provide no benefit to regular fuel apart from a placebo effect from drivers.

When the magainze and other people have questioned the fuel companies about possbly mis-advertising the fuel they use the extra level of detergents as a fall back to justify their advertising of it being `super` fuel, even though it doesnt do anyhting noticable in cars that dont require it.

[speedy231278]

When I was young and naive, I used to swear that my 35 went ever so slightly better and got ever so slightly better mileage on Shell 'super' stuff than ordinary. Now I'm older and fatter and never bother with the expensive stuff. I figure even if there is a miniscule difference, it would be more beneficial in performance for me to lose some of the two or three stone I've gained in the last decade... lol For that matter, if you figure that every time you're almost dry and stick basically 15 litres in the tank, at the roughly 10p a litre difference that's a quid an a half for every fill that's not really giving you any more get up and go. If you're hell bent on getting your current bike to go quicker, you'd be better off sticking the difference in a jar and saving it up for something that will make a genuine difference, like sorting out the jetting, fitting a new pipe, a bit of head work, etc.

[Adderboy]

I don't know about the science, but I always run supreme, no matter what forecourt I'm on, I usually use esso and I get an extra 15 - 20 km, from the bike, tried and tested over many fill ups !

[Malc]

Me personally, I would use 92 from a busy station before 95 from a slow-moving station every day of the week. People who know a shit-load more about this stuff than I ever will tell me its not uncommon for slow-moving "premium" fuel to be so old its nowhere near its original rating. 92 from a busy station and you'll be alright.

[Neosophist]

I think this sums it up the best.

Octane and power

It's a common misconception amongst car enthusiasts that higher octane = more power. This is simply not true. The myth arose because of sportier vehicles requiring higher octane fuels. Without understanding why, a certain section of the car subculture decided that this was because higher octane petrol meant higher power.
The reality of the situation is a little different. Power is limited by the maximum amount of fuel-air mixture that can be jammed into the combustion chamber. Because high performance engines operate with high compression ratios they are more likely to suffer from detonation and so to compensate, they need a higher octane fuel to control the burn. So yes, sports cars do need high octane fuel, but it's not because the octane rating is somehow giving more power. It's because it's required because the engine develops more power because of its design.
There is a direct correlation between the compression ratio of an engine and its fuel octane requirements. The following table is a rough guide to octane values per engine compression ratio for a carburettor engine without engine management. For modern fuel-injected cars with advanced engine management systems, these values are lowered by about 5 to 7 points.



Compression ratio

Octane



5:1

72



6:1

81



7:1

87



8:1

92



9:1

96



10:1

100



11:1

104



12:1

108


The exception to prove the rule. Nowadays, higher octane fuel might actually give you more power but not because of the octane rating itself. Some petrol companies use a denser blend for the higher octane products. Denser blends mean higher energy density per volume (measured in Megajoules per litre - MJ/L). For example:

BP Regular: 32.53MJ/L
BP Premium: 33.08MJ/L
BP Ultimate: 33.28MJ/L

Do these variations in energy density mean you'll get more power out of your engine from premium blends? Yes, but not in a linear fashion - ie. if the premium product has 5% more energy density than the basic product, you won't get 5% more power out of your engine, simply because of the inefficiencies of internal combustion and thermodynamic considerations.


Read more: http://www.carbibles.com/fuel_engine_bi ... z2KMCT2vrA

[speedy231278]

So, according to the chart above, my NC35 that runs 11.3:1 according to the book would produce the most power and/or have the best resistance against detonation using fuel with an octane rating of a little over 104? Isn't that racing and aero engine levels? Meanwhile, my TZR125 with a ratio of 5.9:1 is effectively wasting anything rated over 80-ish?

[Neosophist]

So, according to the chart above, my NC35 that runs 11.3:1 according to the book would produce the most power and/or have the best resistance against detonation using fuel with an octane rating of a little over 104? Isn't that racing and aero engine levels? Meanwhile, my TZR125 with a ratio of 5.9:1 is effectively wasting anything rated over 80-ish?

Not at all, the NC35 owners manual clearly states the bike is designed for 91 octane unleaded. You'd know if you were having problems with your fuel quality as it would be knocking like hell.

That chart wasn't the important part of the article, just the bit on super unleaded being not really useful unless you vehicle can use it, any while some fuels have a slightly denser makeup (slightly more mpg) its often cheaper to get that extra mpg by purchasing regular fuel.

But since you ask, that chart is most likely based on static compression, an actual engine will vary a great deal due to various factors that will affect detonation such as engine load, speed, engine heat, even cylinder head material, valve timing etc. This is known as dynamic compression, is always lower than static compression.

[niteblade]

Wow that was seriously informative...

I have one more question.

What effect does the euro II, euro III or euro IV ratings for fuels have when used on our engines?

I read up that the ratings show the amount of sulphur in the fuels...

Will the lower grade just mean that the exhaust emissions are not so environment friendly, or will it build up carbon in our engines?

[micpec]

So, according to the chart above, my NC35 that runs 11.3:1 according to the book would produce the most power and/or have the best resistance against detonation using fuel with an octane rating of a little over 104? Isn't that racing and aero engine levels? Meanwhile, my TZR125 with a ratio of 5.9:1 is effectively wasting anything rated over 80-ish?

Not at all, the NC35 owners manual clearly states the bike is designed for 91 octane unleaded. You'd know if you were having problems with your fuel quality as it would be knocking like hell.

That chart wasn't the important part of the article, just the bit on super unleaded being not really useful unless you vehicle can use it, any while some fuels have a slightly denser makeup (slightly more mpg) its often cheaper to get that extra mpg by purchasing regular fuel.

But since you ask, that chart is most likely based on static compression, an actual engine will vary a great deal due to various factors that will affect detonation such as engine load, speed, engine heat, even cylinder head material, valve timing etc. This is known as dynamic compression, is always lower than static compression.

also under- or over-jetting, and too hot/too cold type of spark plugs can affect. And even altitude above/under sea level.