what fuel to use in a VZ calais 5.7 V8

[cru]

hi guys,

just brought a 2005 VZ Calais with a 5.7 Litre V8 engine

just wondering what fuel should be using in it, should i be using 98 octane or will 91 be ok for it?

thanks

[m1lky]

I run my ss on 95 or 98. Havnt tried 91, it's probably fine in all fairness

[wadevzss]

If it hasnt been tuned and is running the stock tune, either is fine. You will gain a bit extra in performance and fuel economy running 98. It should make little difference costwise as you should get better kilometres per tank out of the 98.

[fyfee]

I use 98. The PCM has a low-octane and a high-octane spark table. When it detects knocking it reverts to the low-octane spark table and therefore retards timing. Using 98 allows the PCM to utilise the high-octane table, advance the timing, become more powerful and use less fuel because it is more efficient.

You've purchased a (I'm assuming) $20,000 V8, don't compromise performance by cheaping out on the fuel

[Bravotwozero]

If it hasn't been tuned to run the higher rated fuel then personally I don't see the point in using it.

[fyfee]

It doesn't need to be tuned to run high-octane.

It's default is high-octane and if it detects knocking it reverts to low-octane ignition timing

[Brett_jjj]

I use 98. The PCM has a low-octane and a high-octane spark table. When it detects knocking it reverts to the low-octane spark table and therefore retards timing. Using 98 allows the PCM to utilise the high-octane table, advance the timing, become more powerful and use less fuel because it is more efficient.

You've purchased a (I'm assuming) $20,000 V8, don't compromise performance by cheaping out on the fuel

This is exactly right. And you dont need a "tune" for the ECU to be able to take advantage of higher octane fuels. It will do this just running on the standard tune. Theres a lot of people around who dont understand that the ECU can regulate or change the ignition timing, by using infomation sent from the knock sensors, to suit the octane rating of the fuel being used, just like fyfee explained above. I only use 98 octane fuels in my VSV6, and I get excellent fuel economy from it. Ive been getting around 300 km on the highway, for around $20 worth of shell V power 98 octane fuel. The 98 octane fuels work out cheaper, even though I pay more for it than I would for the 91 stuff.

[Berlinarator]

I find Shell V-Power to be the best fuel in my 5.7. Have also tried BP Ultimate, Caltex Vortex & Mobil 8000 but the car runs smoother with V-Power. More fuel efficient too.

[RiCeY]

This is exactly right. And you dont need a "tune" for the ECU to be able to take advantage of higher octane fuels. It will do this just running on the standard tune. Theres a lot of people around who dont understand that the ECU can regulate or change the ignition timing, by using infomation sent from the knock sensors, to suit the octane rating of the fuel being used, just like fyfee explained above. I only use 98 octane fuels in my VSV6, and I get excellent fuel economy from it. Ive been getting around 300 km on the highway, for around $20 worth of shell V power 98 octane fuel. The 98 octane fuels work out cheaper, even though I pay more for it than I would for the 91 stuff.

Its not quite accurate. If it isnt tuned for 98 it wont get the full benefit of it regardless of dual fuel tables. The ECU has no way of reading fuel octane and it only advances timing to a certain predetermined point which isnt high enough to utilise the octane of 98 RON fuel.

[CRUSTIN]

98 is less than 5cents more than 95, compared to something like an extra 15 cents to go to 95. When I went from 91 to 95 I could see and feel the difference, going to 98 didn't do much, but it guarantees that under any heat and load conditions it won't revert to low octane advance.

[fyfee]

Its not quite accurate. If it isnt tuned for 98 it wont get the full benefit of it regardless of dual fuel tables. The ECU has no way of reading fuel octane and it only advances timing to a certain predetermined point which isnt high enough to utilise the octane of 98 RON fuel.

It is still better than 91 though. That's what the OP wanted to know, which fuel to use. 98 is the fuel to use as it provides more power and better fuel economy than 91 and 95

[Munz]

It is still better than 91 though. That's what the OP wanted to know, which fuel to use. 98 is the fuel to use as it provides more power and better fuel economy than 91 and 95

And has way better cleaning abilities for tanks and fuel lines - make sure your fuel filter is new and you'll have no issues