Subaru Impreza II WRX 2001 - Type of fuel

Honest John Back Room » Technical matters
View Threaded
Fri 3 Feb 2012 17:52
Subaru Impreza II WRX 2001 - Type of fuel - garyc923

Hello there,

Hopefully this will clear a lot of uncertainty up on the type of fuel to be used in this vehicle.

Upon searching the internet, a lot of online forums state you must use super unleaded in these. Reading the back of the handbook though states that fuel used in turbo cars must be at least 95 RON.

As two well known supermarket chains sell normal unleaded with a rating of 95, then I would hope that I would be okay using this.

My question is, does anyone else have knowledge of this fuel debate in Impreza's through experience, or hearsay???

Thanks,

Gary.

Reply | Report as offensive | Link
Fri 3 Feb 2012 18:11
Subaru Impreza II WRX 2001 - Type of fuel - RT

All filling stations sell 95 RON, that's just ordinary unleaded.

Like most petrol cars built in the last 15 years, the Subaru's engine ECU will automatically adjust the timing and fuel delivery to optimise whatever fuel is used so that more power will be obtained at full throttle when higher octane fuel is used.

The grey import Subaru's are usually set for 101 RON and won't adjust automatically down to European RON levels but can/should be modified at time of import to run on 98/99 RON.

Most internet debate about Subaru's will include both official and unofficial imports so will confuse many discussions on fuel octane - this is made even worse if North American owners are in the discussion as their octanes are measured differently, using PON/AKI which is 4-5 lower than RON octane.

Confusing, isn't it?

Reply | Report as offensive | Link
Fri 3 Feb 2012 19:17
Subaru Impreza II WRX 2001 - Type of fuel - garyc923

Thanks for that. Makes it a bit easier to understand. I'm running a standard UK car so I think i'll just stick to the regular unleaded and treat it to a bit of the 'good stuff' once in a while, when my wallet allows!!!

Reply | Report as offensive | Link
Fri 3 Feb 2012 20:16
Subaru Impreza II WRX 2001 - Type of fuel - craig-pd130

As a long-time member of Scoobynet, the general view there is that Tesco Momentum 99 octane is the best fuel. Scoobs really do put out quite a bit more power on this stuff, according to various dyno runs etc on that site.

Reply | Report as offensive | Link
Sat 4 Feb 2012 00:16
Subaru Impreza II WRX 2001 - Type of fuel - unthrottled

Turbo petrol engines do benefit from extra octane-when on boost. Most of the time you will not be on boost-so it's a toss up as to whether you'll miss the extra few horsepower. But, contrary to popular beilef, you don't get an extra 5% economy at part throttle on higher octane fuel.

The biggest factor in the onset of detonation is intake air temperature. So while the ambient temperatures are low, save your pennies and use supermarket swill. My brother's Volvo 2.5 Turbo runs just fine on 95 Octane-and he hasn't had to scrape deposits off the valves once!

Reply | Report as offensive | Link