Fuel money saving idea - use super unleaded?

bicycle_repair_man_2

super unleaded doesn't improve your cars mpg or make it run smoother, this is a myth. the only cars that you MAY notice a SLIGHT improvement on are high performance turbo engine cars, eg Nissan Skylines

tomstickland

As I said, it could make a small difference on a normally aspirated engine that advances the ignition further to take advantage of the higher octane rating.
So it isn't a "myth", but it is also unlikely to make a decent different to most people.

AdrianHi

tomstickland wrote: »

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.

I think that sums it up most succinctly.
For these modern cars you need to check your cars manual for the range of fuel grades it will self adjust to. My wifes Mazda 6 is probably typical and will self adjust for 91 to 98 RON, a modern petrol BMW will take anything from 86 RON (lowest grade in the USA) up to 98 RON, easier to churn the same engine and control system out the factory for all markets. Both these cars will return best performance and /or fuel economy on 98 RON depending on how they are driven. Higher RON than this is of no benefit. Tescos 99 RON fuel is usually a good buy as it is about the cheapest 98+ RON fuel available.
I know of someone (an engineer in the car industry) who experimented over an extended period of time with different fuel grades in his BMW E39 540i and eventually settled for buying 98 RON because it just about worked out cheaper on average over a period of months.

meester

AdrianHi wrote: »

I think that sums it up most succinctly.
For these modern cars you need to check your cars manual for the range of fuel grades it will self adjust to. My wifes Mazda 6 is probably typical and will self adjust for 91 to 98 RON, a modern petrol BMW will take anything from 86 RON (lowest grade in the USA) up to 98 RON, easier to churn the same engine and control system out the factory for all markets.

This is not the case, USA does not measure Octane in RON, they use PON, which is RON + MON / 2. 86 PON is roughly 91 RON. So both cars in fact claim the same operating octane parameters.

Hintza

Since this thread started I have been doing some reading about the benefits of V-Power Diesel and from my reading the jury is out. Some say they see improvement both in terms of power and economy whilst others notice no real benefit.

The problem I have is I don't have any set routine to try and get as close to a control experiment as possibe. If I could get 4mpg extra it would be a win that would equate to just under 20%!!! Other problem is my filling station doesn't stock it yet.

I tried super unleaded before and felt thart my old Merc ran a bit better but I doubted there was any improvement in mpg.

As for all your technical stuff ..........your losing me now.....:(

AdrianHi

meester wrote: »

This is not the case, USA does not measure Octane in RON, they use PON, which is RON + MON / 2. 86 PON is roughly 91 RON. So both cars in fact claim the same operating octane parameters.

Thank you! I've learnt something new there.

This has a good general explanation:
http://en.wikipedia.org/wiki/Octane_rating

AdrianHi

Hintza wrote: »

Since this thread started I have been doing some reading about the benefits of V-Power Diesel and from my reading the jury is out. Some say they see improvement both in terms of power and economy whilst others notice no real benefit.

The problem I have is I don't have any set routine to try and get as close to a control experiment as possibe. If I could get 4mpg extra it would be a win that would equate to just under 20%!!! Other problem is my filling station doesn't stock it yet.

I tried super unleaded before and felt thart my old Merc ran a bit better but I doubted there was any improvement in mpg.

As for all your technical stuff ..........your losing me now.....:(

I use Millers Diesel Sport 4 additive in "regular" diesel which gives the same results as BP Ultimate Diesel and Shell V-Power. Over the last couple of years I've found more people (including myself) reporting improvements with BP UD than V-Power, but when looking at the characteristics of the two fuels (in as much as you can from info on the internet) they should be the same. It can be quite difficult to measure an improvement because the improvement you could expect to achieve is around 5% to 7% which is 2 to 3mpg on a typical 47mpg 2.0 diesel. There are a lot of other things than can change fuel consumption by 5% to 7%, the weather for example, I find heavy rain can cost me a couple of mpg, how long I sat in a traffic queue one morning compared to another and so on.

dannyboycey

Sounds like a valid idea which might be worth a try.

There is a definite, maked difference in power in my car when filling up at my local Tesco and local BP (both regular unleaded) - so it would be fair to assume that super unleaded will alter performance somewhat.

Pew_Pew_Pew_Lasers!

bicycle_repair_man wrote: »

super unleaded doesn't improve your cars mpg or make it run smoother, this is a myth. the only cars that you MAY notice a SLIGHT improvement on are high performance turbo engine cars, eg Nissan Skylines

Think you're wrong there. My TVR with a Rover V8 engine and distributor would grumble when fed on anything less than Shell 98.

darich

bicycle_repair_man wrote: »

super unleaded doesn't improve your cars mpg or make it run smoother, this is a myth. the only cars that you MAY notice a SLIGHT improvement on are high performance turbo engine cars, eg Nissan Skylines

Audi A4 2.0 TFSI manual states that if the car is run on standard unleaded then there is a slight loss of power so it's not limited to the type of car you specify.