In the MK4 manual it says you can also use 97 octane, but does that mean you cannot use any higher than 97 ? Or is that just because 97 was the highest there was in 1997 ?

Anyway, here is the question, could I use 99 octane on the 1.25 engine ?

There was a discussion about this over on HJ a few months back.

The general opinion (backed up by in depth tests on super bikes)was there was no benefit to be gained.

The engines ran as normal,there was no change in power or acceleration .

On newer cars the engine management system will self adjust to compensate for the higher octane rating

Why do you want to put 99 in a 13 year old car?

dave

Because I want the car to last as long as possible and want it to run at its best.

The only thing it will do is make your wallet lighter. It won't help your engine in any way. Stick to standard 95 fuel and save your money.

OK, are you sure there are NO benefits ? Not even 1% ? Tesco's MOMENTUM99 has tests to prove it increases MPG on most hatchbacks, so won't it do anything for the Fiesta ?

The tests carried out by Tesco were on new modern day engines which will be able to notice the change in a higher grade of fuel. Your 13 year old car wont be able to tell the difference, and if anything will burn it up even faster than normal fuel.

Your car wont suffer using 97ron, it was designed to run on unleaded fuel so it will do just that.

Tbh your car will show next to no differences in performance/economy when you drive it.

I fill mine with V-Power every few fill ups to keep the engine clean, but atleast with mine the power is so much smoother, runs smoother, better economy and more power.

So just to summerise use 97ron its fine, but if you wish you can use 99ron or whatever :)

So will using V-Power or equivalent keep my 1.25 clean ?

It has been proven that v-power/BP ultimate/ high octane fuel will keep the internals of the engine cleaner than a standard 95ron, yes

watch this for tests on petrol

Well in that case I will use 99 Octane to keep the engine clean, even if that is all it does! And also I will use INJECTOR CLEANER with every tank.

fifth gear did a test on "fuel additives" google it, very interesting results