Hello,

My 2005 GT Vert with automatic transmission is set to arrive in 3 days and I just cannot wait. I had a question about the proper fuel to use. I am currently living in Kuwait and there are only three octane options available here : 91, 95, & 98. There is only one state owned gas station chain so there isn't too much choice (although i can't complain at $0.74/gallon of the 98). http://www.knpc.com/knpc/product_oils.html

I understand that the GT is "designed" to run on 87 octane, so what will happen if I give it 91? Or will 98 be better? I asked the Ford dealer here in Kuwait and they didn't even seem to understand my question (retards ), and told me to use whichever i want as it will make no difference.

Can anyone lend some useful advice about this? One last thing to take into consideration is that Kuwait's altitude is sea level, and I understand that this increases the octane rating of fuel (which might explain why the cheapest gas here is 91).

Thanks,
Mike

 

I don't know if your octane rating in Kuwait is the same as the US octane rating. There are some differences from place to place, so check up on that.

If the octanes you listed are the same as US spec, then just go with the 91 octance. Octane prevents detonation, and nothing else. using higher octane than necessary doesnt add power or add any other beneficial effects. the 91 octane is more than enough for your Mustang, so anything else is really just a waste of money (although at 74 cents per gallon, who the hell cares?!?).
If you were driving at high altitudes, you may need to increase your octane, but at sea level, you should be fine. Have fun with your car and welcome!

 

It's not the same rating. In the US, our pump octane is also known as the Anti Knock Index. It is an average of the gasolines ability to resist early ignition. Anti Knock Index = (R+M)/2

It's an average of the gasolines ability at low speed (R) and at highspeed (M). Two tests are done using a specific engine at low load (RON) and one in an engine under heavy load (MON). Since our rating is an average that is why the sum of the two values is divided by 2.

Gasoline sold in the UAE and Europe is based on the RON--it's the (R) in the above equation.

The numbers come out like this:

US 87 is equivalent to UAE 91
US 90 is equivalent to UAE 95
US 93 is equivalent to UAE 98

I'm no expert. Perhaps someone else can corroborate this.

 

Many countries outside the US only use the RON octane numbers. The US requires that octane be specified by the (RON+MON)/2 method

RON grades are 91, 95, 98 which are equivalent to US 87, 89, 91

This is also why you keep hearing the myth that other countries have much higer octane fuel than the US. Same octane fuel just measured and reported different.

 

 

Thanks for all your replies I'll stick to the 91 (87US).

Cheers

 

• The "R" and the "M" in (R+M)/2 stand for:
  • "R" = Research. It is the study of the average molecular composition of the fuel. An ideal fuel would be C8H18, and is commonly known as Ethyl. If it were C8H18, then it would be the "perfect" fuel, and would have a Research Octane rating of 100.
  • "M" = Motor. It is the actual operational resistance to knock, as determined in a single-cylinder test engine. The test was developed by the Ethyl Corporation long ago (1930s or so).

Octane rating does not affect the total heating value of a gasoline. It only affects the resistance to transition from the normal burning flame-front speed (about 500 fps) to the knocking, or explosive, flame-front speed (about 2,000 fps).

Ford designs their engines to take advantage of the presence of slightly higher than minimum-required octane, and would do so by advancing the timing, and give you a little better power and economy. I would always put the best stuff in the tank that you can buy, which will allow the engine to run more smoothly, especially with an automatic transmission. Ford engines do gravitate to being set for a very slight pre-knock grumble at the lower RPM bands with minimum-required octane fuel (for maximum fuel efficiency). With an autobox that will keep the RPMs as low as possible, you might notice this grumbling.

When I used to work in a Service Station, we didn't have "Premium" gas; we would always "Fill it with Ethyl". Why, we even had a poster of a lady dressed all in green with that slogan. Oh well, days gone by. Now we all just "get it yourself" at the gas station.