Which Petrol to use? Advice please

eddie864

I noticed a much better low down pull on my Honda VFR800 using the higher octane fuels over the standard unleaded. I assume that because it has computerised fuel and ignition mapping it adjusted the timing and the fuel injection system to suit the faster burning fuel. It didn't work out any cheaper but it definitely felt like it had more torque pulling from low RPM.

I saw a roadtest feature on some TV car program where they tested three high(ish) performance cars for differences between a number of different 98 RON fuels against the standard unleadeds. The differences were so small they couldn't say whether there was any benefit at all. Of course, unless your engine can adjust it's own timing you won't benefit from the faster burn rate of the higher octane anyway.

Ultrasonic

eddie864 wrote: »

Of course, unless your engine can adjust it's own timing you won't benefit from the faster burn rate of the higher octane anyway.

I wonder if you're confusing the cetane rating of diesel with the octane rating of petrol? Higher octane fuels don't 'burn faster', the opposite is closer to the mark:

http://en.wikipedia.org/wiki/Octane_rating

The OP referred to the claimed cleaning properties of more expensive fuels as well as mpg differences. Is the consensus here that there are no real difference in this regard?

CKhalvashi

Ultrasonic wrote: »

I wonder if you're confusing the cetane rating of diesel with the octane rating of petrol? Higher octane fuels don't 'burn faster', the opposite is closer to the mark:

http://en.wikipedia.org/wiki/Octane_rating

The OP referred to the claimed cleaning properties of more expensive fuels as well as mpg differences. Is the consensus here that there are no real difference in this regard?

Our fleet manager says 19.2 instead of 18.7 when she tried it (she's got a Merc SL500).

Not worth the extra cost to get 0.5mpg extra, IMO.

CK

Ultrasonic

chunkychocky wrote: »

I fill up my 2001 VW Polo TD once the red light comes on (always have done from it being new). With Tesco diesel I can do 410-420 miles on a tank, Shell ordinary diesel I can do 420-430 miles on a tank, and Shell Nitro+ (or whatever the new stuff is called) I get 450-480 miles on a tank. Speaks for itself as far as I am concerned. Interesting that not everyone finds similar results.

Is it possible that the nitro fuel (absurd name!) has a better anti-foaming agent so that a larger volume of fuel can be put in before the pump stops filling? If so then that would be another problem with trying to judge fuel economy on a per tank basis rather than a proper brim to brim measurement.

red_eye

pedrothefish wrote: »

Had my hyundai i20 1.2 nearly a year been running it on supermarket petrol asda and morrisons. I've been told by a mate that I should use shell petrol because the additives clean the engine and gives more mpg, is this true?
I'm going on holiday next week probably do about 500 miles would it be worth filling up with the V power or regular unleaded?
TIA

octane is the level of resistance of combustion, 95 is easer to burn then 100. This is useful if you run a modified engine say with a very high compression ratio (C/R) the extra heat generated can cause pre ignition which can melt pistons.

some high performance cars have a map that will retard the ignition, igniting the mixture later will cause a bigger and hotter flame front (instead of wasting some of the air fuel mix to propagate the flame front by igniting it as the piston is near the end of the compression stroke)

So if you dont run a very high C/R or have a ignition map that can use high octane fuel, dont bother with V power it wont do a thing for mpg

Ultrasonic

I'm fairly confident the OP's friend was talking about Shell's Fuelsave Unleaded not V-Power...