Effects of ageing fuel on octane rating and motor

**Phantom Snail** · 30-01-2007 07:57 PM

Hi guys,
i have a question in regards to fuel.
Ive filled up a full tank of BP Ultimate towards the end of october last year...there was just over 3/4 of a tank according to the fuel gauge before i put it into storage for a trip and i just got back...so now the fuel is abit over 3 months old...
I was thinking that most likely the octane rating has dropped...
1 - would this be a correct assumption?
2 - so being a lower rating of octane, it cant be too good for the motor?
3 - what should i do about it? I was thinking about siphoning it out, but thats over 30 litres of fuel.. which is too much.. i was also thinking about putting abit of octane booster n some injector cleaner into the tank - but ive heard that octane boosters would do even more damage n harm to the motor.. and i dont want to drive it even granny style until the fuel is gone because im afraid it would do damage to the engine...

Any help is greatly appreciated...

Cheers

**aaronng** · 30-01-2007 08:05 PM

You might as well top it up with more Ultimate (or whatever 98 octane that you like). That's better than octane booster for sure.

**silver_screen** · 30-01-2007 08:08 PM

if its been a tad over 3 months.. the octane rating wouldnt have dropped by much at all...

Instead of being 98 its probably around 97ish.. it takes more than a 3 months to kill fuel

Ive had fuel in my rx7 for about 7 months now

and its still ok... sort of..

**silver_screen** · 30-01-2007 08:10 PM

oh and btw... what kind of motor is it???

If its just a street car.. your engine will be perfect no matter what the condition of the fuel might be (unless its been watered down.. or over 10months)

**Phantom Snail** · 30-01-2007 08:24 PM

Originally Posted by aaronng

You might as well top it up with more Ultimate (or whatever 98 octane that you like). That's better than octane booster for sure.

Mmm but like 5-10 litres of bp ultimate wont really make much of an effect on 35 litres of "stale" fuel would it? so then thatd be like 35 litres or so of "stale" fuel mixed with about 5-10 litres of new fuel.. still bad for the engine overall isnt it?

Originally Posted by silver_screen

oh and btw... what kind of motor is it???

If its just a street car.. your engine will be perfect no matter what the condition of the fuel might be (unless its been watered down.. or over 10months)

Its a b18c7 with a few mods...no aftermarket ecu tho...just apexi neo..

**silver_screen** · 30-01-2007 08:33 PM

Then it'll be fine.. they dont need a diet of extreme fuels

Even my heavily modifed rx7 live without the good stuff for a short while

**EuroAccord13** · 01-02-2007 09:50 PM

Fill up the tank.. Drive it and empty the tank and you'll be fine...

Fuel goes off in like 2 weeks...

**string** · 03-02-2007 05:41 PM

Originally Posted by EuroAccord13

Fuel goes off in like 2 weeks...

Yet it still runs my engine after 6 months... amazing! I must have filled with BP Magical instead of Ultimate last time.

Some evidence for your claim please?

**aaronng** · 03-02-2007 06:06 PM

Originally Posted by string

Yet it still runs my engine after 6 months... amazing! I must have filled with BP Magical instead of Ultimate last time.

Some evidence for your claim please?

Goes off, but still usable. LOL, you need to learn not to take things literally. I drink milk that goes off. Yummm.

**EuroDude** · 03-02-2007 06:11 PM

I had fuel in my civic for like 6 months, no probs with the fuel at all.

Although I did use 95RON in a 92RON tuned engine

**yfin** · 03-02-2007 07:49 PM

Provided fuel is stored in a relatively sealed environment it will last a minimum of 6 months. In 3 months the RON in your fuel has hardly changed enough to be worried about.