High octane fuel and the truth

[Stressball]

I know for a fact that 95 octane made a huge difference in the driveability of our 1984 Ford Meteor, on 91 it was gutless and prone to stalling within the first 15 minutes of driving. Struggled to pick up speed, felt very sluggish, even when it hit the torque spike. After filling it with 95 octane, the idle became smoother, the acceleration certainly improved, no more sluggishness and no more stalling. That being said, it could be that engine in particular enjoying the benefits, it's not really a comparison to a modern day EFI engine.

 

[danja]

I know for a fact that 95 octane made a huge difference in the driveability of our 1984 Ford Meteor, on 91 it was gutless and prone to stalling within the first 15 minutes of driving. Struggled to pick up speed, felt very sluggish, even when it hit the torque spike. After filling it with 95 octane, the idle became smoother, the acceleration certainly improved, no more sluggishness and no more stalling. That being said, it could be that engine in particular enjoying the benefits, it's not really a comparison to a modern day EFI engine.

Was is designed for leaded petrol? I used to have an 1985 Corolla which was made for leaded, but when they stopped selling leaded I started running it on unleaded. On 91 it would ping, and feel gutless, but on premium it would run as it was supposed to. Was also a carby engine, not EFI.

Of course the science of this is clear, the tetra-ethyl-lead compounds in petrol were an anti-knock agent, effectively giving leaded petrol a high octane rating, higher than 91 and the engines were designed with this in mind.

 

[doowy]

I had my 5.7 tuned on caltex 95 mainly cause i live in the country and 98 is a bit rare round here and when i fill up on 95 my distance to empty reads around 770 ish and when i find 98 and fill up only reads around 600 ish.
Just throwing it out there.

 

[danja]

I had my 5.7 tuned on caltex 95 mainly cause i live in the country and 98 is a bit rare round here and when i fill up on 95 my distance to empty reads around 770 ish and when i find 98 and fill up only reads around 600 ish.
Just throwing it out there.

Might sound odd, but perhaps the 98 nozzle is longer than the 95 nozzle where you fill up?? (do you always fill up at the same place for 98?)

The distance to empty is based on your recent fuel consumption (over the last 300 or so kms), and the volume of fuel in your tank. The car has no way of "knowing" what type of fuel you have in the tank, so either your fuel consumption just happens to have been high before filling with 98 or you fill up with less when you do.

 

[doowy]

You could be right, I always try to use caltex fuel not always the same servo but most of the time.The mob that tuned the car said being tuned on 95 always use at leat 95 and 98 would be better . I dunno, just noticed it when i switch between the two.

 

[danja]

You could be right, I always try to use caltex fuel not always the same servo but most of the time.The mob that tuned the car said being tuned on 95 always use at leat 95 and 98 would be better . I dunno, just noticed it when i switch between the two.

There is no reason it should give worse economy on 98 than 95, it might not be any better, but shouldn't be any worse. Try recording the actual distance you get next time on each, the DTE isn't always that accurate.

 

[doowy]

Yeah it does jump up n down a bit ill set the trip next time.

 

[vulkus]

I have a VE Berlina, with only about 70k on the clock, I just did a trip up to my brothers place at Gin Gin in QLD. I used E10 95 going up, and Premium (most likely 95) coming back and it made only a marginal difference. This is because my car was, previous to my ownership was a commercial rego'd city dweller.
I drive combined, both hyway and town speeds.
The VE data as taken from redbook.
Series VE
Body Sedan
No. Doors 4
Seat Capacity 5
Transmission Automatic
Gear Location Floor
Drive Rear Wheel Drive
Fuel Type Petrol - Unleaded ULP
Recommended RON Rating 91
Release Year 2008

Mine is an Automatic and the VE can use and is suitable for E10, and as E10 comes in 3 flavours 91, 95 & 98. I suspect all VE's are tuned to accept high ron fuels. (check the engine handbook, that is where it states what fuel is suitable)

If you own a manual you will almost always get better fuel economy depending upon how you drive your vehicle.
Mostly I ride a motorbike my old honda is particular about fuels and octane ratings, my newer Kwaka doesn't care.
The Honda gets about 200km/tank on vortex, 230km/tank on 91, 250/tank on 95 and 270km/tank on BP ultimate.
This bike is high compression and runs twin carbs and elec ign.
My Kwaka is a 1000cc tourer and it doesn't care what you put in it, it will always return the same mileage. (except with E10 though I don't use it due to the carbs.)

How you drive your car and maintain it is a deciding factor in your fuel economy. Tyres at correct pressure, no excess weight, A/C on all the time or off. How you pull away from the lights and the way your brake when pulling up. Excessive idling to 'warm up' the engine, oil viscosity, engine tune etc all help determine your economy. Putting in a K&N filter can improve the breathing capabilities of your engine and it becomes more responsive and this is often misinterpreted as a performance increase.
The same goes with high flow cats and exhausts, your not really increasing your power, just increasing the chances of that powers ability to get to ground.
I derestricted my pipes on my kwaka 1000, and sure it sounds meatier and feels more responsive, but it didn't give it more power. It just allowed me greater access to that power. Power increases are often misconceptions unless properly diagnosed on a dyno. Back yard tunes and burn outs do not equate to power increase. Just megga fun.

 

[VR38]

2. Premium fuel is not 'better quality' or cleaner than normal unleaded.
Believe it or not, all fuel comes from the same place. It is all refined and then put into storage containers. Chemists then add chemicals to this fuel to determine what it will be called ie. Premium, ultra, regular etc. In fact, premium fuel has more chemicals added to it than regular unleaded.

Believe it or not but PUPL actually is a more highly refined product, costs more to produce, agreed it comes from the same crude oil but so does diesel and LPG.
It is higher octane more so because of the refining process, and less to of all the extra additives.

Agreed that your engine will only obtain benefits upto what the compression ratio will return.

 

[mainpath]

When I use e10 i find i get longer distances in city driving, equally as responsive as 98 however the second i go out of the city or do any long distance driving, it doesn't compare.
91 is honestly garbage, car is totally unresponsive, sudden movements in the car causes a good 3 second delay, car shakes, and general poor fuel economy.
98 on the other hand i've noticed that is runs far better, can't feel the car vibrate, good fuel economy on long distances (~8L / 100km 110km country / highway driving)
Far more responsive, however increased fuel consumption in city over e10 but not as much as 91.

That was for the VZ Commodore, Otherwise I find the Kingswood works far better on 98 then 95, also more responsive, I get around 400km to a tank with fuel additive.
The VB Commodore I haven't really experimented with but when i got the car it was running on 91 with fuel additive and I also noticed the car was shaking a far bit, once I put 98 in with fuel additive I notice a big difference in overall responsiveness of the car.

Edit: I should say I have experimented with a range of 98 petrol from various stations and i've found that Shell & Mobil have the best quality, On the other hand i've bought 98 form caltex, BP and others and found that it was very poor quality, so i guess it's hit and miss.