95 ron v 99 ron question

Aerial Andy944

The Torque Meister
Points
527
Location
Sunny South Somerset UK
Car
VW Golf GT TDi 200
Searched some threads on here but can anyone clarify for me. My nearest super unleaded supplier is a Tesco 12 miles away from me so probably over a gallon of fuel to just fill up and get back home. Can I use 95 ron fuel in a Skyline, although frowned upon, or will this mess up any ecu mapping or damage the engine at all? Can I use 95 ron as a top up to get me down the road nearer to civilisation to get 99 ron stuff? Not worried about cost of fuel or consumption just the logistics of getting the higher grade stuff without having to plan my journey to go at some point past a super unleaded garage.
 

SLEEPER

Pro Tuner
Points
562
GTRs are not cheap to run but when you drive them you appreciate why.High power turbo engines , especially rb26s need high octane because of the way they run.

Unless the car has been mapped for 95 ,which is possible , it is risky running any rb26 on 95 unless you can drive around without boost . (and if you can do that you shouldnt be allowed to own it )

Yes RBs can run on 95 but whenever you boost you are taking a risk and if you are running more than std 0.6 boost that risk is multiplied many times.

Bearing mind an engine rebuild will cost you a minimum of £4-5K to me its a no brainer.

But can you put it in as an emergency as long as you stay off the loud pedal most definately yes . But why would you ?

Instead of running on half full and topping up when the light comes on I fill mine up full and when i get to about a third full look for a tescos.
Ity doesnt cost you any more in the long run.
 

gummy

Torque Master
Points
27
Location
england heathfield
Car
skyline r34 gtt
as standard would the ECU not retard the timing to allow for the 95 ? iknow some engines will do this, obviously at a lose of performance.

granted if its been played with i can understand it not playing as nice

Not sure!,but i suppose in theory their should be some leway!for fuel difference!
 

SLEEPER

Pro Tuner
Points
562
No car can tell the ron of the petrol as it is put in the tank .
So the only way that the ecu can "help" is to retard the ingition by using knock sensors which can signal the ECU to retards the ignition when there is an issue . And the GTR does have this

The problem is that unlike most twin turbos GTRs dont have sequential turbos but two smaller ones working in parrellel - that is why they boost up so quickly .

Using low ron petrol could could be a problem as on boost the engine can det before the ecu can stop it.

And the more you tune the car the more this is a problem .

Thats why mapping is IMHO the most important mod on an RB26 for performance and safety .
Some of the aftermarket ecus give out knock readings for this very reason.
 

Aerial Andy944

The Torque Meister
Points
527
Location
Sunny South Somerset UK
Car
VW Golf GT TDi 200
Thank you very very much Sleeper and Waynne that has been most helpfull and potentially saved me ££££s There was only half a tank of 95ron in the tank which I put in when I picked car up from the garage late one evening last week (why do garages never leave you with any fuel to get home :mad:) I've found a Shell garage that's a bit closer, about a 15 min drive away, that doesn't advertise it has VPower but has a pump in the corner. Us country folk only have diesel vehicles out 'ere you know "oooh arrrr" :lol: I'll fill up and hopefully that'll mix it up enough for now. Got a replacement coilpack going in today as found one of the new ones was faulty causing the slight misfire which the wrong fuel may also have been contributing to :confused:
I've even left a rep score for ya :amuse:
 

MasterAuron

Very Senior Member
Points
242
Location
379bhp 359lbft
Car
Mk1 Focus RS
Nothing to do with injectors tbh, no.

Wise words from SLEEPER in here. It can be done, but it's not worth the risk. If I was using a 97+ car daily (the FRS is but it's only a second car) I would keep a bottle of octane booster just in case I got caught short.
 

Olley

Track Warrior
Points
182
Location
Ruislip, England
Car
E30 touring 325i
sorry to thread jack, but what octane do you recommend for a 1990 BMW E30 325i auto with 207k on the clock? it's the 2.5 litre M20 engine if that makes a difference?
 

Olley

Track Warrior
Points
182
Location
Ruislip, England
Car
E30 touring 325i
Would you say it would be a bad idea to run the higher octane?

and can someone correct me if I'm wrong, but I believe I've seen 105 Ron at the pumps. near Santa pod I think....
 

pgarner

TC ModFather
Points
417
Location
Lockerbie, SW Scotland
Car
Octy smoke machine
look in the manual and see what it says, if its 95 theres no real benifit from running higher. most ECUS can retard the timing through the knock sensors but none can advance it as far as im aware.

yeah 105 is getting to race fuel, would have been aroundf a £5 a litre or something
 

obi_waynne

Administrator
Staff member
Moderator
Points
1,157
Location
Deal, Kent UK
Car
A3 1.4 TFSI 150 COD
I don't think it is an expense. In my car I get more miles from a tank and better performance from super unleaded so the cost factor balances out nicely.
 

SLEEPER

Pro Tuner
Points
562
ITs not injectors
To clarify 95 can be a particular problem with gtrs because RB26s can spool up soooo fast in lower gears.
And because new they were designed for jap feul which is high octane.

But as long as you know you are driving with 96 stay off boost and you will be fine in the short term.
 

Aerial Andy944

The Torque Meister
Points
527
Location
Sunny South Somerset UK
Car
VW Golf GT TDi 200
Replacement coilpack fitted, it's running so smooth again. Picked up some octane boost from Opie so that should see me straight for this tank and problem will be solved. Thanks again for advice, I know what I need to do now :bigsmile:
 
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