How "Super" Is N.Z. Petrol?

Press, Volume CIII, Issue 30395, 20 March 1964, Page 9

How "Super" Is N.Z. Petrol?

VVHAT are the grades of . petrol used outside New Zealand, and how does New Zealand’s “high octane” fuel compare with that available overseas, a correspondent asks. In modern cars with high compression ratios, he says, “its performance is disappointing, to say the least” .It is correct that our 93 octane is not a “super” fuel by overseas standards. It is also true that many modern can, both big and small, are designed to run on fuel nearer 98 octane, but still, if correctly tuned, they should run satisfactorily -on 93 octane, although not giving the full performance of which they are capable. The exceptions are many of the sports cars and some of the higher performance saloons, several of which are most unhappy on fuel with such a low octane rating. The world-wide trend is towards higher compression ratios and higher octane fuels and whereas a compression ratio of 7.5 to 1 was considered high a few years ago, 8.5 to 1 or even 9 to 1 is not uncommon today. The 79octane fuel which was the

only petrol available la this country compariatively recently is regarded overseas as being of intolerably low grade. Simply, octane rating is basically a fuel** resistance rating if you like. The higher the compression that can be used in an engine—the tighter the piston can squash the mixture—the more power the piston, and thus the engine, will deliver on the downwards stroke after the ignition of the mixture. Thus, the more efficient the engine, the more power produced for each unit of fuel. Taking Britain as a good example of overseas conditions: such terms as “super,” “premium,” and “extra” mean nothing, and can be largely ignored. This is because one petrol company’s “Super” may have a totally different octane rating from the “Super" distributed by another company. British Grades

Using more general terms, regular grades in Britain range from 89 to 91 octane on the standard laboratory test used to determine octane rating. Thus our “super” petrol

in New Zealand is a little better than the regular or

commercial—the lowest and cheapest grade-available in Britain.

The next grade up is mixture, ranging from 92 to 94 octane—almost the exact equivalent of our high octane fuel. As a matter of interest its pNce. in Britain ranges from 4s ,3d to 4s 6jd a gallon as against about 4s 4d for

Premium grade (4s B}d to 4s 9jd) ranges from 96 to 98 octane, and is recommended

for the majority of new cars. A particular exception is light vans, which, being mainly for commercial use, are generally designed to tolerate mixture or regular fuel. Super grade (4s 9jd to ss}d ranges from 99 to 101 octane. It is the fuel generally specified for sports cars and high performance saloons. Knocking or pinking can, in severe cases, wreck an engine. The grade of fuel needed is governed by the design of the engine. Thus, it would be a waste of money to run a 1936 car on 101 octane, but running a high-perform-ance sports car on our 83

octane could damage it Contrary to common belief, using a fuel of unnecessarily high octane rating in an engine will not damage it Thus the driver who uses 93 octane in his 1930 model will not damage it—he will merely be wasting money. Compression ratio is not the only factor governing the sort of petrol needed, and the best authority is the car manufacturer. It is of interest that in recent tests in Britain a B.M.C. Mini, Consul Cortina, Hillman Minx, and Vauxhall Velox were tested with different grades of fuel. The Mini was the only one which would run on the regular (89 to 91) grade, and even then its ignition had to be retarded to prevent knock.

Much The Same The tests, conducted by the Consumers* Association and reported in “Which?”, showed that in 1600 test runs no difference in performance was found between several different brands of fuel. Nor was any difference in economy found.

However, it was found that

the top grade of one company might differ slightly in octane rating from the same grade of another firm, and two samples of the same brand of fuel might also differ considerably. There is no reason to believe this would not be the same in New Zealand. The tests, however, did show differences between brands in volatility and cleanliness. A surprising number of fuels had a gum content which was far too high. It was also found that the customer did not always get the advertised brand of petrol from any one pump at some stations, but there is no reason to belive this, occurs in this country. The testers concluded it was possible one brand of petrol might suit a certain car better than another brand ”... perhaps because the car manufacturer used that petrol when developing his car’s engine.” They also commented “You are much more likely to get better service from your car by careful maintenance than by changing the brand of petrol you buy.”