Difficult to start on Premium

LANKY 1 · 05-02-2010, 01:23 PM

I filled up with Premium fuel for the first time (to see what it's like) and now ive noticed it's even harder to start, sometimes it's the 3rd time trying to start it it actually starts(cold), slightly better when warm. I'll prolly go back to using normal fuel after this. seems odd it would be harder to start with beter fuel?

Dauphin · 05-02-2010, 02:02 PM

Maybe you should try resetting your ECU if it's had up to 10 years of running on lower octane fuel.

1. Disconnect and reconnect the battery.
2. Start and put trans in Drive (or 1st if manual) with air con on for 2 mins.
3. Turn off air con for 2 mins.
4. Put it in neutral with air con on for 2 mins.
5. Turn off air con for 2 mins.
6. Drive it around at varying throttle positions for 5 mins.

See how it goes over the next 100 kms.

LANKY 1 · 05-02-2010, 03:12 PM

what's the point of putting it in 1st gear for step 2 and 3, cos the clutch will have to be in anyway!!

And not sure if it has been 10 yrs on normal fuel, it's also duel fuel (always starts good on gas) and ive only had it a year now
havn't tried it on gas since ive fueled up yet.

**SSD-85** · 05-02-2010, 06:45 PM

I had this same problem with my xr6 vct.

The science of higher octane fuel in this case is basically premium burns slower and more controlled and is less "explosive". This is good in high compression situations as it prevents instability and chances of detonation. Also, higher octane fuels require more energy to initiate a reaction, so as far as the AUs low comp 6 goes, this would explain the need for additional cranking, given LPGs ron is around 110 probably explains why AUs take forever to start on gas too. I summise that unless your engine is set up to run higher octane, then it is unnecessary to use it.

Halfmo Rocks · 05-02-2010, 11:40 PM

i recently started using premium in my standard I6...i figure if performance engines demand it, it must be better than regular unleaded - and then a month or so later, the servo i usually fill up at abandoned regular unleaded for some ethanol blend. i've never had a problem with starting

so it's premium or nothing there...i just don't trust the blend - it may be fine, but i dunno

LANKY 1 · 06-02-2010, 05:32 PM

Thanks scotty, interesting read, just thought i would try a tank to see how it runs, and to give the engine a little cleanout. once running it's great, noticed the exhuast is a little louder and crackles a little more.
will go back to normal fuel after this.

Adam, i'm not sure bout the ethanol stuff either. used it in my old ute, still ran the same, don't want to use it in this one(even if it is cheaper)

Halfmo Rocks · 06-02-2010, 06:51 PM

i'm with you on the unsure state of mind Lanky...i'm just not sure, so i say - mine was made in the factory to run unleaded...not doing conversion to LPG or just filling with ethanol blend, as my car was not made to run either, i'll trust what it was made to do rather than changing fuel types or converting to different fuel type a decade after car was built.

premium is more expensive...but i have more peace of mind with it...misplaced or not