What is 91 octane?

[ChasB]

Tried searching here, but with no luck.

I've got two Volvo V8 petrol engines and have been happily filling her up with whatever I can get my hands on (she runs well on the cheaper variety of Russian vodka).

Just noticed that the manual says "Use petrol with 91 octane (Research Number) with or without lead."

Should I be doing anything different?

 

[alienzdive]

91 Octane is unleaded fuel.

 

[ChasB]

cheers.

 

[ChrisE]

I think you'll find that it has nothing to do with unleaded, more to do with anti-knocking. 91 octane is regular, rather than premuim grade fuel. Here's probably more than anyone needs to know about the subject.

 

[ChasB]

from that site:

"In the UK, the most common petrol types are:

Ordinary unleaded - 95 RON
Super unleaded - 98 RON
Leaded Four Star - 98 RON"

So where does that leave me with my 91 engines? My interpretation is that I shouldn't pour in anything under 91, so 95 and 98 are OK...?

And what is cheap Russian vodka rated at? Will Red Bull do the trick?

 

[Guest]

You should be using straight Unleaded ....

Also note that many web-sites refer to older Octane ratings that prevailed before .... especially if you see any reference to Leaded or LRP ......

You can expect to get a result of 92 - 95 on straight unleaded and 95+ on Premium. Do not confuse RON with MON - they are different ratings.
Also beware of any quoted ratings that mention Infra-Red / Portable Octane Testers .. the standard is via a proper set-up Octane Engine ... a simple but heavy engine designed to have its timing etc. altered to produce knocking and so the rating can be calculated .... why in the biz we nickname them Knock Engines .....

Basically .... it would be hard for anyone in UK now to get high enough Octane gasoline to hurt your average car / boat engine - unless you have access to Avgas (aircraft gasoline ....) and also similarly low enough to pink average car / boat engine now ...

Unlike over here - where we can still buy the old 76 MON ( about 82 RON) and other grades up to 98+

 

[ChasB]

Excellent!

You da man!


I am so envious of your move.

 

[Guest]

Unfortunately - its my main biz ...

Fuel labs and quality .... along with Marine stuff ...

 

[ArthurWood]

[ QUOTE ]
Tried searching here, but with no luck.

I've got two Volvo V8 petrol engines and have been happily filling her up with whatever I can get my hands on (she runs well on the cheaper variety of Russian vodka).

Just noticed that the manual says "Use petrol with 91 octane (Research Number) with or without lead."

Should I be doing anything different?

[/ QUOTE ]

I have two Mercruiser V8 petrols and the manual says to use not lower than 87 octane, which is the regular grade in the US. (US goes 87/89/93). I've been using 87 for 1400 hours and they are still going strong. The only thing the manfr says not to do is use petrol containing alcohol (seriously) so don't think using vodka is giving them a treat /forums/images/graemlins/smile.gif

 

[ChasB]

I'll just have to drink it then...

Cheers (hic!)

 

[Guest]

Alcohol ....

Here they are talking about Ethyls, Methyls, Pentanes and other boosting products termed under the Oxygenates and Alcohols when blending ...

Sorry to say it but US is one hell of a place to say no alcohol in gasoline !! I know of various supplies into US that have blends that contain the above ... Commercial Confidentiality prevents me from naming - sorry.

All Gasolines contain varying amounts of alcohols and boosters ... it's how much - not whether they are present. (Vodka aint one of them !!!)

 

[KeithH]

91 octane (RON) was the old regular petrol in the UK. It was phased out in EuroIV regulations, which came into effect in 2005. So the lowest octane in the UK, and I think in the EU, is 95 octane petrol (gasoline). - and that is all unleaded. You wont do any harm in using a higher octane petrol - but you wont necessarily get any benefit. Too low an octane than the engine is designed for, however , can cause pre-ignition (pinking) which can do damage.

So 95 RON will be OK.

 

[brianrunyard]

Tesco's Super Unleaded is stated as being 99 Octane.
Shell Optimax 98 Octane.

 

[VicS]

[ QUOTE ]
Tesco's Super Unleaded is stated as being 99 Octane.
Shell Optimax 98 Octane.

[/ QUOTE ]

And I think most if not all of the others are 97.

I run a very old car that does not like anything below 98, unless the ignition is retarded a bit but it does not have to be leaded. Setting it for premium unleaded is just, but only just possible, and sometimes I have had batches of that which it pinks on so I generally avoid filling it right up so that if necessary there is room to add a gallon or so of super. If it was a "performance" car I would use the super all the time but it was not available everywhere at one time and possibly still is not.