91, or 93 Octane Gas

[EquatorHeat00]

Can I run the car on 91 octane instead of 93, or will it hurt performance? (Also been using only 93 octane since Nov. of 1999 does that matter?) Gas is expensive now, so was going to put in half a tank of 93, and half a tank of 89 thus making 91 octane.

[Craig 94 TA GT]

CA only has up to 91. Thus I've been running 91 for years and the performance has been great...no pinging at all either.

[Injuneer]

It definitely will not hurt the engine to run on 91. You may see some very minor power loss, if you are getting any knock retard as a result.

Different octane levels are available in different areas of the country partly as a result of the elevation. You need less octane the higher the elevation. With DE being essentially at sea level, it is possible that on a very hot day (increases octane requirement) you might see some knock retard. Your car is old enough that you might have some carbon builup (increases octane requirement).

The only way you would know would be to monitor the PCM with something like a ScanMaster, that will give you real time readout of retard. It isn't likely you would ever hear "pinging", since the knock sensor hears it way before you could, and the PCM retards the timing.

[Screaming mad]

Oh my... our low octane fuel over here in the uk is 95 octane... super unleaded is 97 to 98... no wonder people always say its expensive! 93pence litre..

[Joe K. 99 Zeee!!]

Running a lower octane fuel with knock retard should result in lower gas milage as well, right???

[Injuneer]

Oh my... our low octane fuel over here in the uk is 95 octane... super unleaded is 97 to 98... no wonder people always say its expensive! 93pence litre..

In Europe, you use a "different" octane rating. You are using what is referred to as "Research Octane". That is determined using a test procedure that consitst mainly of "normal" driving. Nothing aggressive.

The other test procedure used to measure octane is called "Motor Octane". That is a measure of the fuel's ability to resist detonation under very heavy loads, more representative of performance driving. It isn't unusual for Research Octane to be 10 numbers higher than the Motor Octane number.

While you use "Research" in Europe, in the USA we use the "average" of the "Research" and "Motor" numbers, expressed on the pump as (R+M)/2.

That would explain about a 5 number difference between what you see posted on your pumps and what we see posted on ours.... same fuel, different method of measuring the octane rating.

[Jeanius]

Is it ok to use octane boost you can buy from the parts store?

[96Camaro]

Hmmm....I read somwhere one time that if you were to mix lets say 91 octain with 89 or somthing like that, the octain rating would not be 90, it would actualy stay lower then that.

[lt14mla]

Is it ok to use octane boost you can buy from the parts store?

Ive used a bunch of these and have noticed no difference in gas mileage or even performance whatever it might be. Not worth the 5 dollars. Go get yourself another gallon and half of gas instead

[Screaming mad]

is there any way I can measure the octane of fuel at home? i often mix octane booster for my bike and car.. my bike was designed to b run on 100octane in japan! just wondered if there is anyway of using hydrometer etc to measure octane? or does it have to be under load as described above (ron/ mon / average)

[Injuneer]

No. Measuring "octane" rating is an extremely complex test procedure, requiring the fuel to be run in an actual "standard" engine.

[Joe 1320]

Here is some interesting reading on brewing your own high octane fuel. I've done this for yours with my GN, maybe some of you can use the info.

http://www.gnttype.org/techarea/misc/octanebooster.html

[Screaming mad]

thought it sounded too easy, just been to 2 paint shops, closest they got is gallon drums of toulene xylene methanol mix! can not very discriptive so could contain other products? also i dont know in what percentages there in?