What is the difference between unleaded 95 & 99 petrol? Is there benefit to using 99 in a car built in 1990?

Answer 1

Mmm

There there will only be a benefit if the engine was designed to have one.
Most engines are designed to run on a range of octanes.
Some need to be told which you are using so the ignition timing can be adjusted. There may be an "Octane Plug" or similar in the engine bay. Check with the manufacturer or look up your excact engine model.
It is most likely that there will not be any benefit of the change.
If you were to get the car tuned to run best on the 99 it might make a little improvement. Many cars are tuned to a median value and use their ECU and sensors to change the ignition timing for better performance dynamically, but this depends on the engine.

Have a look at this example on octane ratings for a Neon
http://faq.neons.org/faq/FAQ_ET.html
And this paragraph
"This apparent gain in power is due to the ECU of the car’s ability to advance the ignition timing to take advantage of the extra power the higher octane offers. Looking at the air/fuel ratio on the charts does show that the higher octane fuel allows a more efficient burn creating more power.
from here
http://www.pistonheads.com/news/default.asp?storyId=14919



Good Luck !

Answer 2

There is no repeat no advantage in using high octane fuel in cars designed for lower octane fuel. High octane fuels burn slower under pressure than low octane fuels and on average contain slightly less energy. There is no repeat no difference in purity especially by the time the fuel gets trans-shipped through tanks and transporters to the tanks at your local fuel merchant.

There is no repeat no connection between the age of a car and the octane rating it needs unless of course if the engine is very old, like early 50s or pre-war. If the engine is in good condition and the compression ratio is high enough, it will require a higher octane fuel than a newer car with a lower compression ratio.

Some old engines built for high performance in the 1940s and 1950s are now difficult to use because they were designed for very high octane leaded fuel which is no longer available.

The best guide is the owner's manual. If not available, check websites devoted to the particular make and model. You might have to register and you might find out a bit more about the car which could be useful.

Maybe you can get a straight answer from a dealer but I would not hold my breath unless you get the car serviced there.

Answer 3

All of those answers are pretty complex... here is an easy one:

Look at the owner's manual... it will tell you exactly what octane to use. It is okay to go over the prescribed level; however, it will be a pretty bad choice to go under.

For example; my 1988 Chevy Beretta calls for 88 octane, i can go over no problem. My 1996 Mustang on the other hand call for 91 octane, never will i go under... if i find some 95 or 99 at a reasonable price, freakin awesome, i'm fillin' up.

All in all, look at the manual.

Answer 4

95 and 99 RON refer to the octane rating of the petrol, and its ability to resist pre-ignition. A car's need for higher octane-rated petrol is related mainly to its compression ratio, and the shape of its ignition advance curve.

Cars with high compression ratios and steep advance curves generally require a higher octane rating to prevent pre-ignition (pinking).

If your car is a fairly standard and untuned saloon or hatchback (Cavalier, Sierra etc.) that happily accepts unleaded, then 95 will do.

If your car is something like a Sierra Sapphire Cosworth or an Escort RS Turbo or similar, then you really should go for 99 octane.

If your car has been 'tuned' for performance (cams, CR, exhausts and filters etc.) then you should be guided by the engineer who did the work, and a rolling-road diagnostic test.

There is no benefit in using 99 RON petrol in a car that doesn't need it.

Answer 5

99 ron petrol burns more efficiently than 95 ron but it costs a few p more. In a 16 year old car theres no point spending the extra money on 99 ron petrol.

Answer 6

95 and 99 refer to the level of octane and the purity of it, for a car of that age 95 would be perfect

Answer 7

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Answer 8

They are different octane ratings. The higher the number the slower the fuel burns. If your car is designed to run on the lower octane fuel there would be no advantage to running the higher octane.

Answer 9

Not unless its a super car most run of the mill cars run on 95 octane .

Answer 10

Here in North America, 95 is about as high as we go without "mixing" our own fuel. I wonder if Europeans have a different system than ours, or all your cars are high performance.