Unleaded vs Super Unleaded petrol.

davemorton

I used to run optimax in a S2000, but then it was recommended that you used 98 + RON. Cant say I felt much difference when using 'normal' fuel, but then again, it was only rarely that I did. Other uses in the forum I was on did report a difference, in both performance and MPG.

Shimrod

BMW 325 - tried two months on Shell optimax, and two months on Asda standard petrol. That's about 4000 miles on each type of petrol - no difference on fuel economy at all.

brazilianwax

Paradigm wrote: »

Keep 'em coming Anyone with an Impreza, Evo or other high performance car noticed a difference between 95 ron & 98/99 ron?

(it's not recommended to use 95 in an evo )

I've an Evo 9 :A and she never EVER gets less than 97 RON . I wouldn't do it! :eek:

Shell Optimax is her favourite, but she gets the occasional top up of Tesco 99.

ohreally

My MX5 NC gets Tesco 99. Idle is smoother, no doubt about that but anything else is open to debate.

jeannieblue

Shell Optimax for an Impreza. BP ultimate for high performance Ford.

I only ever put BP in my boring Focus and it runs far better than when I used to put cheap stuff in. It costs a tad more but I get more for my money so it is worth it.

Jakg

After lots of testing on an empty motorway, my car runs slower on BP SuperMegaUltimate versus Shell Ordinary...

EDIT - my car = Proton Wira which has a 1.5 Mitsubishi engine design from the early 90's.

rottertron

Normally unless youre car has been modified to take the advantage of performance fuel, you wont get any advantage. Alot of modified turbocharged engines require high octane fuel as the ecu can easily be remapped to take advantage of the higher grade fuel.
Cars now have "knock" sensors that alter the igintion if youre running low octane fuel for the car, therefore not to damaged the engine.

AdrianHi

Moderns car with ECU's (Engine Control Units i.e. computer controlled) through the afore mentioned "knock sensors" are able to self tune ignition timing to suit fuel grades from something like 91 RON (available in the USA) up to around 98 RON. Some performance cars can go higher.
In theory using a fuel at 98 or higher should give better performance and fuel consumptiom. In practice I've never been able to measure a difference.
I have measured a worthwhile difference on fuel consumption with premium diesel fuels though...

Tim_Nicholas

V power or other higher octane fuels are only really beneficial in Jap import cars (their fuel is all 100 RON out there and ECU's are expecting the higher RON) or Turbos or larger engined.

for the general run of the mill standard cars, good to run a tank of V power through every 1 in 4 or so.

Throbbe

Paradigm wrote: »

Keep 'em coming Anyone with an Impreza, Evo or other high performance car noticed a difference between 95 ron & 98/99 ron?

Never ran anything other than Optimax in my Legnum, although the knock sensor/ECU would have kept things safe. Seemed a bit daft to buy a high performance car, spend loads on insurance/servicing etc and then scrimp on fuel.

Decision of Optimax over other higher octane fuels was backed up by a few experienced tuners who claim Optimax gives the best knock resistance despite not having the claimed RON value of Tescos. That said, there are respected tuners that recommend Tescos unleaded, so that's not cut and dried by any means.