91 to 98 Octane, I can't feel a difference

[noobie]

Hi All,

I know the fuel discussion has happened beforem however, i want state that when i fill up my car with bog standard Unleaded 91 Octane I cannot notice and difference to when i fill it up with Premum 98

Is it bad for the engine running a lower octane fuel. I have a 2007 Astra H sri Turbo.

Cheers
B

[Greg K]

unless you got a case of bad fuel when you filled up with 98, you should feel a difference... i know i did when i had my v6 veccy. It ran like a slug with normal 91 and didnt get close to the fuel economy of 98.

The thing with 98 is its a "cleaner" fuel, so it is better for the longevity of engines.

Did you notice a difference in fuel economy??

Cheers
Greg K

[oneightoo]

when i put 91 in my impreza, it gets flat spots everywhere.. 98, it runs perfect - after the 91 is flushed out that is..

also get more km's per $$

[btm]

defintiely notice the difference in both the astra and the bike. smoother and more economical

[DirtyHarry]

you might need to give it a few days for th ecu to adjust itself.
when you put the 98 in, the ecu will pickup different knock sensor values and will keep advancing the engine to the limits of the new fuel.
in turn advancing the engine will give it a very slight power increase, etc etc.
i think with the astra, all you really need is a 95 ron fuel.

[Hoss]

According to the Astra H SRi-T owners handbook you should use 95 RON as a minimum. When I put 98 RON in my standard SRi-T I could barely notice the difference. The Vauxhall TIS2000 workshop manual states that running 98 RON in a standard SRi-T won't make any difference. That said, 98 RON is supposed to be better for the car as stated above. TMS (and other tuners) recommend 98/99 RON for all turbo cars. If you are going to modify the car for greater performance, then IMO use 98 RON.

Putting 95 RON rather than 91 RON in my wife's N/A Astra G did make a noticable difference in performance. Her handbook advises there will be minor HP and torque gains from using 95 RON - it's a much better car to drive, no flat spots etc, and seems to get better fuel consumption.

[CNBLU]

Why would you put 91 into a turbo car??

The difference in price is not that much

[gman]

As Gav said, "Why??"

If there was any fuel in the tank then it would have mixed and you get a slightly higher octane depending on what was in there.

If you want to see the difference, find a long, steep hill and cruise up to it at 40KPH in 3rd gear as soon as you start going up the incline, floor it.

The lower octane will mean one of two things: The ECU will pull timing and/or it will pull boost and you'll get an EML light as the engine starts pinging itself to death.

It only gets worse the hotter the weather gets...

IMHO, drive carefully and empty or get to half a tank and fill/refill with 98.

Crap fuel in a turbo car during summer = possible engine damage

[Klunke_DK]

I wouldnt run 91 in a turbo. You run a major risk of detonation, and that will "smash" flat spots in your conrod bearings and you put excessive stress on your pistons and headgasket. Most likely you will end up with a conrod thru your engine block if you continue this, especially if you run it with boost. My advise would be to put some octane booster in it ASAP and then run it on 95 like the manufacturer says you should.

98 octane does nothing for it, if the manufacturer recommends 95. The major difference is that 98 have a higher detonation value over 95.

So unless you start running higher boost or compression you shouldnt need to run 98. However they ad alot of additives in the 98 octane to make it "super" so it will clean your injectors and keep carbon buildup away from your valves and so on. But driving your car hard does the same thing.

When the weather gets hot (35+) then you will have higher temperatures and that might push 95 into detonation rather than ignition. There is deffinantly noises to listen out for, but during summer i would recommend you to run 98. Its a cheap insurance...

Also if you find yourself constantly reving it into the high RPM's 98 is strongly rcommended.


But changing fuels does take some time for the ECU to control. 2 - 3 tankfulls.. Quick way around that is to disconnect the battery earth for about an hour. I dont know what the reset time for the Opel ECU's are, but an hour should be a nice long break and that should deffinantly reset the ECU to default injection and ignition.

[mania]

As the manual says, you're safe running 91... as long as you're very gentle on both revs and throttle. But why on earth would you use it as a daily fuel with those restrictions?

[btm]

revs and throttle ftw! :p

[Wraith]

Hi All,

I know the fuel discussion has happened beforem however, i want state that when i fill up my car with bog standard Unleaded 91 Octane I cannot notice and difference to when i fill it up with Premum 98

Is it bad for the engine running a lower octane fuel. I have a 2007 Astra H sri Turbo.

Cheers
B

Interesting, you should feel a difference going from 91 to 98 especially in a forced inducted engine, even if it has been tuned for 91...

As others have said, you won't feel much if any difference going from 95 to 98...unless you start to tune the engine up, then there will be a noticeable difference going from 95 to 98...

Are you using Shell fuel by any chance ?? reason I ask is because they only have 95 or 98, unlike other brands which have 3 types, so their regular would already be 95 and that's why your not noticing any difference...

As others have also said above, there isn't much of a price difference from 91 to 95 and even less if you use vouchers, so I too recommend at least using 95 once again in a forced inducted engine, it's a very good idea to do so...:)

[USC]

Trying revving and driving your turbo hard on 91..You ll kill it in a couple of months.

On new cars, you dont usually feel much difference between 91 and 98. everything is new and works 100%..therefore power difference is minimal.

[noobie]

Jeepers,I had no idea that the fuel was THAT important.

I'll go fill her up with the normal V-Power that i normally use.

I suppose one day i went to the service station and thought "i'll see if it makes any difference" so i put in about 10 litres of 91 octane into a reasonably empty tank. :eek:

Couldn't really feel any difference in the car.

However, now i have read from a few of you that it could actually be very detrimental to the engine i will go back to my 98 Vpower ful time.

Thanks for he replies.

Again, I was doing it out of curiosity with no comprehension that I could actually damage my engine. :blush:

Thanks for the feedback all!!

[mania]

If you didn't notice a difference between 91 and 98 you likely won't between 95 and 98, so may as well run 95 :).

That'll be fine... just don't run 91 long term in these ;).

[GreyRex]

If you didn't notice a difference between 91 and 98 you likely won't between 95 and 98, so may as well run 95 :).

That'll be fine... just don't run 91 long term in these ;).

+1

I agree. Considering the price difference even between 95 and 98, I don't think it's worth it (on a stock turbo like ours).

I bought my car new and was averaging around 10.5-10.8 every tank for the first few thousand kays, and used Shell V-Power 98 every time.

I've now done 38,000kms, and am averaging 9.5L every tank, but have also switched back to 95. Along with the engine becoming more worn in over time, I have not noticed a single difference in performance. If anything it feels stronger now on the lower grade fuel

If that's any difference for you...