What Octane Petrol for 4L V8

cookster · 10th November 2011, 08:25 AM

Hi all,

I have had my 2003 V8 for just a couple of weeks now and have been using the 95 Octane "premium" unleaded, but wondered if anyone out there uses the 'normal' unleaded which I think is 91 octane, whether it runs ok or whether this should be avoided?

thanks

Mark

**Cannon** · 10th November 2011, 08:38 AM

My 2003 V8 runs on anything. I even tried E10 & it went very well.

I now run LPG & put 30-40l of 98 every couple of months.

**georgesadlik** · 10th November 2011, 08:47 AM

I run 98 nearly all of the time and only lesser fuel when 98 is not available. IMO these engines run better on it. Lately i've been trying to run only the BP Ultimate 98 and have found it to be very good. I've had a few mechanics also recommend that these engines prefer higher octanes due to engine pinging.

It's a personel choice really.

Cheers

George.

**PhilipA** · 10th November 2011, 08:55 AM

Check the compression ratio stamped between 2 and 3 next to the engine number.
If it is 8.13:1 ( or near that,I think they changed slightly in the 4.0) then use normal 91 octane unleaded.
If it is 9.35 use 98 octane.
D2As changed at some point from 8.13 to 9.35.
Regards Philip A

**Rocky88** · 10th November 2011, 09:04 AM

You should use at least 95 octane fuel in all European cars.

**101RRS** · 10th November 2011, 09:06 AM

Originally Posted by Rocky88

You should use at least 95 octane fuel in all European cars.

Why?

A 4.0 low compression engine runs fine on 91 Unleaded. I believe the handbook also indicates that as well.

Garry

**PhilipA** · 10th November 2011, 09:37 AM

Unless an engine has knock sensors AND is high compression AND the ECU is configured to run on 95 or 98 it is a waste of money to run on 95 or 98 and it may run worse on warm up phase.

A D2A with Thor has knock sensors but if low compression will run happily and maybe best on 91.

The owner of a high compression will know if he has 91 as it will ping quite a bit before retard is actioned, unless the driver has cloth ears.

One of the execs where I worked at NSW ag had a D2A high compression and was always complaining of pinging even on 98.
Regards Philip A

**AussieAub** · 10th November 2011, 09:38 AM

Originally Posted by Rocky88

You should use at least 95 octane fuel in all European cars.

Disagree. However I do agree with garrycol's statement.
I only use 91 octane in my D2, as using anything higher makes it run like a bag of poo. I know coz I've tried it a few times as per peoples suggestions on this forum, and kept going back to regular.

My manual says 91 and it runs perfectly fine, while saving many many $$'s at the local rip-off servo's.

**georgesadlik** · 10th November 2011, 09:58 AM

Ok, i've got a 4.6 high compression motor. If that makes a difference ? With a lumpier CAM as well plus a tuned ecu from Bruce Davies. 98 for me it is.

Cheers

George

DM74 · 10th November 2011, 10:03 AM

Thats a funny one - same cars but always variations in performance. I dont think this is unusual. I tried 91ron and it felt very 'flat' and economy seemed to always be up around the 18l/100klm plus mark.

Went to 98ron ( I agree, I'll use BP or Caltex whenever possible) and picked up bottom end response, cleaned up a niggly rough idle, and AT LEAST got the % extra cost back in economy.

I recon you've got to try both ways but run 6 to 10 tanks before making a decision on which way to go - I was told this by an engine management expert from Ford.

Note that the 1999+ 4.0 V8's as far as I know are recommended to run 95ron - as most euro cars do. Havent heard about the low comp model - D1?
Also, better fuel has additives such as injector cleaner etc - another saving that will catch up with you at some stage unless you pop a bottle of cleaner in regularly (whatever that is?)

98ron for me!

regards
Darian

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