improving fuel efficiency

[project.r.racing]

E10 is unlikely to save anything according to Drive tests done a drew years ago. Some vehicles are not suitable to run on E fuels- including MX5?

The fuel itself isn't more economical in that it is used at the same rate as normal fuel.
However it tends to be cheaper than regular fuel, so the running cost is lowered.

I dissagree with that statement. E fuels trend to have a higher usage in normal cars. So while you might save 2 cents a litre, your fuel usage will go up. All of my cars see an increase of 8% fuel usage while using E10. Or 11 cents compared to 91/95 fuels.

I always do a E10 fill once every month or two just to attempt to clean you the system. So pretty much done heaps of fuel usage trails. 3 cars, and they all loses similar amounts. 97 BP1.8 323, 07 MZR2.0 3, 11 MZR2.3 Escape.

So save 2 cents at the pump, but fill up more. In my situation, using E10 means a cost increase of 9 cents per litre.

[Red Dragon]

Not that I use it in the NC but there is a factory sticker inside the filler flap that E10 is ok to use

[Blade_Hunter]

My understanding is that a 98 octane fuel will give a very slight power increase. Even though it costs more to buy you put your foot down less to get the same power which in actual fact makes it cheaper per K but more expensive per litre.

This will vary from car to car, my GT will do 12 l/100 on 98 and 14 - 14.5 on 95. My Dad's Vitara does 11.4 on E10, 95 and 98.

Of course there are many other factors like traffic and even if you just felt like giving it a boot full that day but overall I find better economy on 98

[Mr Morlock]

I reckon you will struggle to prove better economy( $ per KM) by using premium fuel like 98 - the petrol cos certainly prefer you upgrade. RAVC reports always signal the need to use 98 as a negative.

[chrisearl88]

Octane is a measure of the fuels knock resistance, the higher the compression ratio, the higher the octane requirement. Using higher octane fuel than that called up by the manufacturer does not produce more power, as the octane rating has nothing to do with the energy density of the fuel. By using a lower than recommended octane, most modern engines will have a knock sensor which will retard timing which will result in reduced power and economy. All comes down the what fuel the engine is tuned to use.

E10 or E85 for that matter is less energy dense per unit volume that regular 91 octane petrol!E10 will result is worse fuel economy, but it comes down to how much worse and is this offset by the fuel being cheaper.

Ethanol blended fuel does however have a higher octane rating by as the ethanol component has an octane of around 108RON.
E85 is able to produce high power outputs due to its octane (knock resistance) and is especially suited for high boost turbo applications, the only catch is much larger injectors/fuel pump are needed to deal with the additional flow requirements.

The best way to improve fuel economy is
1.reduce weight
2. brake less
3. smooth and light throttle input

In saying that i hit the redline most days, but i still get around 10L/100km so the fun factor is well worth the extra $, An extra 2L/100km is only $300 a year if you do 10,000km a year and fuel is $1.50!

[Blade_Hunter]

Interesting read: http://www.motoring.com.au/advice/2008/ ... aster-7513

Short version is that the octane rating itself doesn't provide more power but the fact that it is a premium fuel means there may be more carbon to carbon atoms which will result in a power increase.

Also the part about the Saab engine was pretty interesting .

[project.r.racing]

If you are getting any real gains from running higher octane fuels. It's probably because the car is pre igniting less. Which in turn shows you may have had timing issues before using higher ron fuels.

[PL]

Another one that I'm a big fan of is adding IGN timing. This improves fuel economy AND response!

Sure, if your timing is already optimised then you have nothing to gain. But 95% of older cars can handle some extra timing. From stock they're usually set up to run a variety of fuel grades under a wide range of conditions = compromised timing. If you only ever run 98 and you haven't added timing then you're missing out!

I've pretty much done this to every car I've ever owned from my old Datto 180B through to my current SR20DET. It always works. I had a work mate once with one of the old Ford Festivas - I believe they were made by Kia with engine based around Mazda B Series. Anyway, he was one of these guys who writes down his fuel figures every tank - and always used 98. Perfect test case. We advanced the base timing as much as we could (no dizzy - pickup was on crank pulley, so we had to slot the holes). The results were immediate. We ran out of room to slot the holes so he made up a bracket to get even more adjustment. In the end we improved his fuel economy by 4 to 5 mpg (sorry about the olde-world figures). It was getting around 40mpg, so that's a significant improvement. This was also measured over multiple tanks, so it's a solid figure.

I also have a Mazda 121 (the old boxy one) to which I've fitted a B5 DOHC import engine. They're like the B6 in the NA MX-5, but slightly less capacity. It goes like the clappers. Dunno what car it came out of but it's a good engine. Once again I've added as much base timing as it'll take. Made a big difference. I run it right on the edge - in summer it'll juuusssst start to detonate under certain conditions.

Upsides - improved fuel economy and improved throttle response, particularly at part load.

Downsides - Will cause detonation if you go too far. But non-turbo engines will handle a bit of detonation without a problem anyway. Idle speed will usually increase so you need to turn that down again. And they can get very fiesty just off idle - to the point where things become a bit hard to manage when parking etc. My 121 also has a light flywheel, so it's extremely responsive. Which I love. But unsuspecting drivers have had issues!

There's my 2c worth on fuel economy. Get some timing into it and reap the benefits!
PL

PS: Can also be done on turbo engines but you gotta know your stuff or the knock monster will come and break your engine!

[Rocky]

There are at least a dozen key factors that are relevant to attaining 'best fuel consumption' but the single best one for me is still "drive like a chauffeur".
I am able to do this around town as I am retired and can avoid the rush-hours.
When I get out on to the 'B' roads it is a different story and the fuel consumption takes a hammering.