I have been reading some forums of people mixing u98 and e85. I have read the effects of 85 on fuel lines etc but only when running 100% e85. But I was looking at running maybe 70% u98 and 30% e85 or maybe even more 98 comapred to 85. My reasoning is that with the high prices of 98 mixing 85 would be a bit cheaper to run. I drive a 2003 BA XR6 with a redback cat-back exhaust. This is all without a tune etc

Would maybe save you $10 at the pump. Waste of time. Run 95 instead of 98 if your concerned about the price of fuel

Any saving would be good as I drive almost 100km a day 4 days a week. So my fuel does not last long. I was trying to avoid running 95 as my car seems to like 98.

Yaris time.

if you want to run e85 just run 100% e85, i know a few people running e85 for a few years now on std e series and au fuel lines without issues..

but no point running it unless your car is tuned for it..

You can't save money by running ethanol-based fuel.

Pretty much every car made in the past 20 years is designed to handle up to 10% ethanol without any issue. E85 is up to 85% ethanol and typically 105 octane. So you could mix 12% E85 and 88% 95-octane petrol and end up with 10% ethanol and 96.2 octane. Without retuning, you could probably safely push it to 17% E85 and 83% 95-octane, giving about 15% ethanol and 96.7 octane. Using 98-octane as a base fuel, you get 98.8 and 99.2 octane, respectively.

HOWEVER, ethanol has about 30% less energy content than petrol, so you would consume about 40% more (pure) ethanol than petrol to cover the same distance. At 10% ethanol, you will use about 3% more fuel in total. At 15% ethanol, it's about 5% more fuel consumption. A car running all E85 will use about 33% more fuel than it would on straight petrol.

You can (partially) compensate for the extra consumption by increasing the engine's efficiency through a higher compression ratio. But that costs money, which negates the whole purpose of the exercise.

see:
http://www.caradvice.com.au/70035/ethan ... he-basics/

If you want to save money on fuel, without changing cars, driving style is your biggest single influence. Accelerate slowly (but where's the fun in that?), start coasting down to a stop early, gain a little speed downhill and lose a little uphill, carry speed through corners, etc. Look up "hypermiling".
A whole raft of other things will help too:
- increased tyre pressure (about 40-42psi is as high as you can safely go, if you can handle the hard ride)
- use air conditioning as little as possible
- keep your windows closed at highway speeds (you can't win)
- turn off your 1000-watt audio system and any other unnecessary accessories
- take any unnecessary weigh out of the car
- get your wheels aligned
- low restriction air filter and intake
- etc