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Car Talk By Jack Biddle

Informer - Motoring

Question for Jack

Local resident Paula has sent in a question regarding the different grades of petrol available to motorists at the pump and what is the correct fuel required for her vehicle.

I get very confused when I sidle up to the bowser and find there is no 95 octane available for my hybrid car (used import from Japan). I am then told it’s exactly the same as the 98 octane which is available but far more expensive. My question for Jack then is, why do some gas stations not sell 98 and others not sell 95”? It all becomes very confusing to me, not helped by the fact that one forecourt attendant told me that the cheaper 91 octane was absolutely fine to use but then again, I was told by the people who sold me the car initially, not to take the cheaper option. Sometimes I simply don’t believe what I am being told. Am I the only ignorant person on this issue”?

Jack: Thanks for your email Paula and you have every right to be confused about what is the correct grade of fuel to use in your vehicle. Obviously with the current price of petrol and the fact you drive a hybrid in an effort to lessen the pain at the pump, it makes good economic sense to be using not only the correct grade of fuel for your vehicle but also the cheapest.

To be honest, it’s a debate within the motoring industry that has raged for many years with some very strong opinions that can, and do, confuse the poor old end user at times.

One misconception within the trade in my opinion is motorist’s being told that the petrol quality in NZ is poor so the higher the octane used the better. Fuels sold in this country are in fact required to meet a minimum Government standard which is equal or similar to that used in some other countries including Australia, UK and the USA. They are tested regularly to ensure those standards are being maintained so I don’t buy into that theory.

So what is the difference then between the three grades of petrol?

In layman’s terms, the octane rating is a measure of the fuels ability to resist detonation (fuel igniting prematurely) with 91 octane having the lowest rating currently in NZ. Not to say that’s a bad thing, in fact, the majority of NZ new vehicles will happily accept this grade of fuel.

Adding a higher octane fuel to these vehicles will only increase your costs and not deliver any benefits in terms of fuel consumption or power in my view simply because the engine has been designed specifically for the lower octane rated fuel.

At the other end of the scale, 98 octane is made available to cater for the very high-performance end of the spectrum which is in fact in the minority when it comes to mainstream vehicles in our market. Overall then, 95 octane should be viewed as the ‘safe’ option if mainstream vehicles owners are in doubt as to which fuel they should be using.

Owners adding the lower grade fuel to a vehicle which is designed to operate on 95 octane as a minimum, do take the risk of incurring expensive engine damage as a result, particularly if used over a long period. In some cases, the engine management dash warning light may stay illuminated while driving to indicate a problem.

One golden rule to remember is; there is no harm done moving up in octane ratings (apart from your pocket) but not the other way around.

So, no clear answer that suits everyone Paula. A good place to start your particular search is to look for a label advising on what fuel to use on the inside of the filler cap or head to the owner’s handbook (not so helpful if it’s a Japanese used import and recommendations are written in Japanese however). Another option is to go on-line and search for the specific owner’s manual for your vehicle. That will, if you are prepared to look hard enough, provide the recommended fuel grade. Next port of call is to contact the New Vehicle Distributor (regardless of whether it’s a NZ new or used import) or a franchise branch for your particular make/model providing as much detail as possible. Definitely avoid regular trips to those gas stations that only sell 98 in preference to 95 if you are driving a mainstream vehicle that only requires 95 octane as a minimum is my advice also especially if you’re looking at saving on fuel costs.

Note: After a quick search on-line for Paula’s vehicles owner’s manual we found that the use of 87 octane gasoline or higher was recommended which means 91 octane is absolutely fine to use in NZ. A follow up call to the National Head Office for her brand also confirmed this recommendation.

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