Petrol Question.

What's the difference between 95 and 98 ratings? (Apart from price and
octane?)

I've always used 95, but would 98 give me better fuel consumption? Is
it worth the hassle?

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nothing. Price and Octane is the difference.

SWK will be along shortly.

The hassle of picking up the nozzle next to the one you normally use?

 

FWIW, my bindit 'pinks' using 95 and is fine on 98. Otherwise I
dunno.

 

No and no

 

Nothing AFAIK, though a chemist may tell differently

Not unless you have an electronically injected bike with a fuel map
tha can take advantage of the higher octane.


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Well, if it gives me 1mpg better, then cost versus consumption probably
means it wouldn't be worth it.

--
Cab :^) - Ormiga Atomica
GSX1400 - 'Tarts Handbag' (tm) Bike, dead 550/4 Rat
UKRMMA#10 (KoTL), IbW#015, Bob#4, POTM#3

P.S. Remove your_head from the cab. ICQ: 83023471

 

What's the difference between red and blue? (Apart from the
colour[1])?

[1] And the price, obviously.

 

The 98 octane fuel allows the ignition timing to be advanced further
than it could be on 95. This means that more power can be released,
but generally does so at the expense of using more fuel. Using 98 in
an engine not designed to use it will have no benefits and, according
to some, may lead to build-up of crap on the plugs/valves or whatever.

No. _If_ your bike was set up to use it, it would use more, not less,
fuel.

No.

 

Wow, a reply that actually cleared up my question.

Ta

--
Cab :^) - Ormiga Atomica
GSX1400 - 'Tarts Handbag' (tm) Bike, dead 550/4 Rat
UKRMMA#10 (KoTL), IbW#015, Bob#4, POTM#3

P.S. Remove your_head from the cab. ICQ: 83023471

 

heh

 

linked from section 7.2 (but about to move) in the FAQ is the gasoline
FAQ.....

http://www.turborick.com/gsxr1127/gasoline.html

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Quite so. The higher octane might increase power slightly, or might even
make it run a tiny bit smoother, but only if you can adjust the ignition
*and* fuel to make use of the extra octane.

The other problem not yet mentioned is that the higher rating unleaded
fuel does evaporate faster too, and can cause carb freezing issues too.

Seconded.

 

<snip>

Does it ? And why ?

I don't know anything about the volatility of MTBE, the only component
I'd expect to often see more of in 98. So that might be it. OTOH, there
are some fairly light component that have crap octane ratings that I'd
expect to see less of in many 98 octane blends.

If RVP (vapour pressure) can be taken as a measure of volatility, I'm
under the impression that many blends, both 95 and 98, are limited by
this and these would all be the same. (RVP is limited in the
specifications to limit environmental impact from evaporation.)

 

Yes, don't know.

I can remember when unleaded first appeared it took a very long while
before the higher octane rated stuff came out, the problems were well
documented at the time. I think they released it for sale due to demand,
but many older engines suffered with these problems. The difference is
probably minimal for sure, but probably enough to make the difference in
practical use.

I suspect they have managed to overcome these shortcomings with extra
additives.

 

Simian (Simian@in_valid.semi-evolved.org) gurgled happily, sounding much
like they were saying :

Because if 98 gives more power, you need less throttle for the same speed.

In fully-mapped engines with knock sensors to take advantage of the octane
by adjusting the timing, 98 may give slightly better economy.

If the engine in question (car, bike, lawnmower, it's not relevant) doesn't
have a knock sensor, and doesn't pink on 95, then there's no point in 98.

If it pinks on 95, then 98 is worthwhile. A penny or three per litre's
cheaper than knocking a hole in a piston. Alternatively, adjust the timing
to run on 95.

If it has a knock sensor, but it will only retard from a base timing map
that suits 95 (for example, to allow for euro-standard-undeaded 91, which
we don't get), then there's no point in 98.

If it has a knock sensor, and is capable of advancing the timing to use
higher than 95 properly, then it's worth a crack.

 

Simian (Simian@in_valid.semi-evolved.org) gurgled happily, sounding much
like they were saying :

High load is where pinking tends to occur, be that at high revs or
slogging at lower revs.

? It won't "chuck fuel through" and over-richen the mixture - it'll stop
it leaning out, which would cause the cat to get hot. That's separate
from the octane, though. The lambda will ensure it remains close to
stochiometry at all times.

Not necessarily - more and more car engine management is using knock
sensors, not just turbots. Back to the point, though - I don't know
enough about bike engine management, but I don't *think* they tend to be
as sophisticated as car systems. I guess I'm saying that while it's not
likely that the economy will benefit, it's far from impossible,
particularly if you aren't using the extra power to increase speeds.

Well, yes... <evil grin> - but you say that like it's a bad thing?

 

The Guzzi is supposed to use 4 star for lead and octane reasons. The
jury's out on both but mine runs quite happily on UL 95, and has done for
over 40K. Goes well enough without significant timing changes. It uses
a Lucas Rita (Le Mans) electronic box to replace the points and bob
weights.

The times I have run it on UL 98 it /seems/ to be crisper. IYSWIM.

 

Meant to add ...

When I've used LRP it runs like crap and is an absolute fucking cow to
start. Mine has no choke and requires flooding.

I've not used LRP since shortly after its introduction so would be
surprised if the low turnover was a contributory factor. Anecdotally I'm
not the only one that's had this problem.

 

Nice theory, but octane^=calorific value.

Nope. By making use of the anti-knock properties of the higher octane
to advance the timing, you're allowing more power to be produced per
stroke, but this power will only be produced if you open the throttle
more and hence use more fuel.

Quite. Even some/most that _do_ have knock sensors aren't designed
advance far enough to make use of the higher octane, but will just
retard more if you use real junk fuel.

Ah, what I was saying.

Finally. _If_ this were the case, however, the manufacturers would
generally recommend that 98 be used. This is true on my Volvo, for
instance, where they also point out that better fuel efficiency cannot
be achieved with 98.

 

Probably not worth the hasle... Yes you will get a bit more power, but
your economy willl go down and who knows what the long term effects on
the motor may be... HTH.....
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