New Redline Advice - Running In and Fuel RON

[Flying Scotsman]

Thanks for chiming in everybody. I picked up a 'static' demo tonight with 30ks on the clock and very little fuel in the tank. As the sales rep hadn't had time to fill the car we went to the servo together and he filled it, after some presuasion, with a full tank of 98, not 91. I will alternate between 95 and 98 I think and see how I go. Took it for a quick 120km trip with the wife and kids and the fuel gauge has dropped to 3/4 of a tank, which is fine, as its new and I didn't buy this car for economy.
I've skim read the manual and there is a bit on running in on p192..... "no full throttle starts......avoid one constant speed......don't exceed 110km/h" for the first 1000ks. But I can't resist the temptation to give it the odd squirt now and again which I would think the v8 can handle.
Cheers

 

[panhead]

I've always been of the belief the cost balances out as the 98 is more efficient than the 91 and therefore you use less of it.

I know with my tuned cars I’ve always been told to use 98 otherwise it would be better to have the tune backed off and the performance difference is noticeable if I’m forced to use a lower octane than 98.

But Holden having to deal with many types of owners would factor in the lowest common denominator and the car would run unharmed on 91, just nowhere near its best.


In contrast the Owner’s Manual for my C63 says:

Refuel using only unleaded super grade petrol with a minimum octane number of 98RON/88MON otherwise you will impair engine output or may damage the engine.
If the recommended fuel is not available and only as a temporary measure, you may also use premium unleaded petrol, 95RON/85MON. This will decrease engine performance and increase fuel consumption and you must avoid driving at full throttle.
If only low grade fuels are permanently available you should have the vehicle adapted to run on this fuel by the local Mercedes-Benz after-sales service division.

The manual for my twin turbo BMW says something very similar.

The same goes for some of my older carbed cars, fill them with lower octane and they splutter all the way down the road.

Obviously they are higher strung engines designed for performance and not as jacks of all trades where they are just as likely to be used as lazy hacks.

Personally if the end result is less consumption which evens out the fuel cost, I can’t see why you wouldn’t feed it the best available and that way you also have performance on tap if you want to use it.

 

[bradles024]

I don't understand why you'd spend 50k on a ls3 ss and then put 91 in it. 98 is not much more per tank.

 

[Chookah]

I don't understand why you'd spend 50k on a ls3 ss and then put 91 in it. 98 is not much more per tank.

Inside the fuel lid it says "Premium recommend" however I'd say 70% of the time I refill using 91RON (never E10).
Some of us have company fuel cards and are trying to stay under the radar of the accounts dept!

This right here.

 

[crew_man]

Unless you experience pinging and pre-detonation of the fuel, the lower octane won't affect the performance of your car.

If you run a low octane petrol in a car with a high compression ratio (other things such as timing, piston/head design will also play a big part) and the engine experiences pre-detonation it will revert to another tune that changes the timing and other parameters to prevent this pre-detonation. That is why you may experience reduced performance.

The actual difference in energy that is in the petrol is negligible, so it's not a simple matter of lower octane fuels giving you poor performance. It is based on the engine design and tune.

On my vehicles I personally run the lowest octane rating that I can run without pre-detonation, because I want the compression in the cylinder to get the fuel as close to detonation as possible, with the spark plug then setting it off as required, which will allow the energy within the fuel to be released quicker than if a higher octane is used and the fuel is not quite ready to be detonated (slower burn). Given that octane is anti-detonation, I don't want to over-octane my engine, making detonation of the fuel more difficult.

I currently run 98 in my SV6 because the LFX is a relatively high compression motor which doesn't have a catch can (yet) so the PCV vapours can reduce the octane in the mixture. Having the higher octane fuel helps to minimise the octane reduction.

With Euro vehicles, they generally use advanced design and run higher compression ratios and advanced timing for greater thermal efficiency so they require a higher octane fuel, just like forced induction engines. An old school pushrod V8 is unlikely to really need or benefit from the higher octane fuels.


As other people have said, the price difference between high and low octane fuels isn't all that great, so for piece of mind and the placebo effect that comes with higher octane fuels, you might as well go with the higher octane stuff.

 

[Towcar]

Unless you experience pinging and pre-detonation of the fuel, the lower octane won't affect the performance of your car.

If you run a low octane petrol in a car with a high compression ratio (other things such as timing, piston/head design will also play a big part) and the engine experiences pre-detonation it will revert to another tune that changes the timing and other parameters to prevent this pre-detonation. That is why you may experience reduced performance.

The actual difference in energy that is in the petrol is negligible, so it's not a simple matter of lower octane fuels giving you poor performance. It is based on the engine design and tune.

On my vehicles I personally run the lowest octane rating that I can run without pre-detonation, because I want the compression in the cylinder to get the fuel as close to detonation as possible, with the spark plug then setting it off as required, which will allow the energy within the fuel to be released quicker than if a higher octane is used and the fuel is not quite ready to be detonated (slower burn). Given that octane is anti-detonation, I don't want to over-octane my engine, making detonation of the fuel more difficult.

I currently run 98 in my SV6 because the LFX is a relatively high compression motor which doesn't have a catch can (yet) so the PCV vapours can reduce the octane in the mixture. Having the higher octane fuel helps to minimise the octane reduction.

With Euro vehicles, they generally use advanced design and run higher compression ratios and advanced timing for greater thermal efficiency so they require a higher octane fuel, just like forced induction engines. An old school pushrod V8 is unlikely to really need or benefit from the higher octane fuels.


As other people have said, the price difference between high and low octane fuels isn't all that great, so for piece of mind and the placebo effect that comes with higher octane fuels, you might as well go with the higher octane stuff.

Lower octane fuel has a theoretical minutely higher energy potential than higher octane. Pushrod engines can be high compression and require high octane fuel, But the rest of what you have said is on the money

 

[bradles024]

Fair enough

 

[crew_man]

Here is some information on octane ratings and engines:
Regular Or Premium? - Autoblog

They even say: "But increasingly, companies like GM and Hyundai are developing engines that can both take advantage of the performance benefits of premium gas, while still run on regular. And in some cases, even produce nearly as much power. One example is the 430-horsepower LS3 engine in the Corvette. It can run on plain old 87 octane gas, but you'll get a little more out of it if you feed it premium. "

Remember that the octane ratings in the US are different from Aus. 98 in Aus is equivelant to 92/3 in the US

 

[crew_man]

Lower octane fuel has a theoretical minutely higher energy potential than higher octane. Pushrod engines can be high compression and require high octane fuel, But the rest of what you have said is on the money

Correct, but the additional energy that is in the fuel will provide a negligible real world benefits. The benefits that one would actually receive come down to engine design and using the fuels that it is designed/tuned for. Using higher octane fuels in a low-compression engine that is designed for low octane fuels will not have you seeing any performance benefits.

True, pushrod engines can be high compression, I was more so referring to the particular LS3 engine in the Commodore in saying that you are unlikely to see any benefit in using a higher octane fuel due to it's design.

 

[gazpep]

I've always used 98 in my VF1 Redline, in fact I try to stick with one brand as the mainstay but will occasionally use another brand just to mix things up a little. I would never use 91 and would use 95 only in an emergency, that's just my cautious nature. I figure the car costing over $55k is worth the premium fuel.
I've pondered using E85, but not sure if the tune is set up for it, I'm aware that the VF1 is flexible as far as fuel is concerned. Has anyone used E85, would be interested in their experiences and feedback...not wanting to hijack the thread though.