Fuel money saving idea - use super unleaded?

thescouselander

I might try a tank of super unleaded next time I fill up to see it it makes a difference in my current car - I'm not that optimistic it will work though.

moonrakerz

I tried all the various types of super/extra/go-further-faster types of petrol and diesel in two (company) Mondeos ans found absolutely no difference, either in performance or mpg.

If you read the wording on the banners/posters in filling stations, the wording of the claims is somewhat "woolly" to say the least !

tomstickland

A higher octane rating can allow more mpg if the engine management is capable of detecting room for more ignition advance. It also allows higher compression ratios, but that's fixed for a particular engine.
An open-loop ECU system like that in my 1991 BMW will not show any improvement.
Bear in mind that the calorific value of Super is slightly lower too, which means you need to burn a larger mass of it to release the same heat compared to Premium.

For most people I doubt it will offer a saving.

Buying LRP at £1 a litre is worth investigating though.

anewman

tomstickland wrote: »

Buying LRP at £1 a litre is worth investigating though.

I wonder if the additives would affect the catalytic converter like lead would.

tomstickland

Probably, but I don't have a cat.

Just looked on petrolprices.com and cheapest LRP within 20 miles is £1.15 per litre!

Keith

I'd been using Super Unleaded in my car since I bought it last year, it was only last week that I read to take advantage of it I needed to advance the ignition timing.

So I filled up with standard unleaded at the weekend and enjoyed saving 5p a litre which it is down here

Belnahua

Quote from :- http://www.videojug.com/film/how-to-fill-your-petrol-tank

"Please stop spreading this myth. Putting super-unleaded into a car that doesn't need it will not improve performance or lead to better mpg. The octane indicates how likely a fuel will auto-ignite, and has no bearing on fuel performance. The myth comes about because very high-performance cars are *designed* to run on higher-octane fuels than normal - not because the higher octane increases performance, but because a lower octane fuel would result in knocking with the compression used. Using a lower octane fuel than designed leads to reduced performance (the engine compensates to prevent knocking), but using a higher octane fuel than is required is just a waste of money."

anewman

I believe most modern cars can control the distributor advance/retard. Don't know if this is just done based on engine speed like the old vacuum method or if it takes into account other factors or not.

steveo3002

on a older car you would have turned the distributor a few degs more to take advantage of the fact the car will run with added timing

newer cars with a ecu have the facility to pull back the timing if low grade fuel is used , but not all have the ability to learn that high octane fuel is used and add extra timing

tomstickland

Most modern ECUs use knock sensors and they advance ignition until they detect knocking and then wind it back in using whatever alogorithm the manufacturer's have developed.