Petrol

Hi
Anybody got any opinions on normal unleaded or super unleaded, ie do you think you get better mileage on super or no difference. Just interested on what people think.

Long ago when super unleaded first came on the market I did a test using my company car. I ran the same destinations over a 2 week period but used super unleaded for the second week. I can't remember the full details but the super gave better MPG but when I translated this into £££'s it was less than the difference between the price of regular and super.
So yes it gives better MPG but not better economy. Haven't done a similar test recently but would doubt if the results have changed.

You could compare costs of super vs regular vs regular + octane booster additive.

I don't know if the latter will make sense economically either, but used to work for a well known petrol additive manufacturer, and the reasearch to back up products claims of engine cleaning etc were pretty impressive.

not tried it in the rangie but in the mrs audi it make a difference in performance with throttle responce and pick up thro the gears but no difference in economy,same on my bike also

I seem to remember reading in the manual of my 4.6 that you can use high octane fuel but it makes no difference. It may be wrong

There is a popular misconception about octane rating. Low octane petrol once ignited burns at just the same rate as high octane petrol. But low octane petrol in high compression engines tends to preignite because of pressure and heat before the spark is applied. Giving pre ignition and damaging your engine. High octane petrol resists this pre ignition in high compression engines and only ignites when the spark is applied. So if you put high octane petrol in your low compression car it will give you diddle scwat. Contrary to popular belief. Octane rating is about when the fuel burns and not how the fuel burns.

Just for info, my P38 doesn't like esso superunleaded, but is fine on ordinary from supermarkets! It coughs and bangs for a bit and doesn't pick up well at all, can't work that out-and it was over an exclusive use full tank. It's best on lpg of course( higher octane still), so I can't work that out, and I'm not going to try!!!

Wammers is spot on about octane rating meaning.

i think super ran better in me classic. dunno if it gave better mpg or was worth the extra.

Engines that have closed-loop ignition timing and are running on the edge of detonation on 95 will benefit, most modern BMWs for example run around with artificially retarded ignition timing through detonation unless you run super. This is why I hate it when magazines use superunleaded by default (usually sponsored) BMW gain an unfair advantage as thier engines are designed to run on it. On 95RON they'd experience a fall in performance and fuel economy, Mr Mondeo won't.

Range Rover V8s are in a soft state of tune and would probably run on 2 star if it was still available! You'd be wasting your money to run super.