Got a '94/95 Ford badged Mazda Courier 2.6ie 4x4 pick up.

It pinged a bit on 91 RON and only got 300kms out of a 50 litre tank
I put 95 RON in and got about 350kms a tank and no pinging. A little better, but the fuel is about 5 cents dearer. Put in 98 RON for the sake of science (and there was no 95 left at the gas station) and got 400kms out of a tank, but the fuel is about 10 cents a litre more expensive than the 91.

Just some useless information.

Well I guess using the 98 and burning less oil is good for the environment.

I use 95 in the camry for the slightly cleaner burn for the engine and environment.  What I tell myself anyway...
Just adding some useless information 

Use 98 in the monster. ..runs better but slightly harder to start. Especially as it gets old...

98 is harder to burn in that low compression motor.

You're just wasting money and sooting things up.

Someone may have mentioned that to me before...

And as usual in my pig headed way I am still using 98 

I am good thay way

Respectively, on the order of a 12% and 20% reduction in fuel cost per km, which is no small thing.

But, depends how far you drive as to whether it's really significant.

Fuel costs as a baseline around $1.40/litre for 91Ron.
Here 95 is around $1.50 and 98 $1.56.
So gains are slightly higher as a %.
In the camry I get a bit under 10% gain from using 95.
So pretty neutral. So better efficiency is still good.

Converting his best numbers over to Yank Units, he's getting 18.8 miles per gallon.

With a mostly highway run, best I got from my '97 Dodge Dakota pickup was 22 mpg.
It was a 2WD with 3.9 liter V-6, purportedly 175 HP.
Not a bad truck, extended cab.
Sheetmetal was paper thin, so the few washes it got were accompanied by a discovery of a flock of new dings.

I have the same ute koko and get the same out of a tank. I've tried all three fuels and find there is no gain out of 98, I've come to the same conclusion on the 95, 91.
Just a side note, mine works for a living and the thing has been thrashed, I just can't kill it, great ute

What year is yours? I think mine must be one of the first efi models.

1999, 320000km, just about to put in it's first clutch, other than that it's all original

Motors seem pretty tough.

..weird.

My DR gets better fuel range on 91

than on 95

(its never been fed 98).

It pinged on 91 which I took as a hint. Must have a fair bit of compression I guess. I was surprised with the 98 economy, but the price is very high for the fuel. The 95 seems worthwhile.

My M900 on 98 gets 230-240 kms from 13 litres. I can make it get less.

Quote from: koko64 on September 05, 2014, 03:51:39 AM
I can make it get less. =

Alternate between 98 and 95 in the car and 95 only in the bike! Its happier all round and now my fuel economy will be down by a 5th 95 is all it'll get!