Fuel Experiment with a 6L

[UFO]

A really interesting thread topic, but the results are already in folks.... the best fuel to buy is Regular Unleaded, followed by E10, followed by Premium Unleaded.

Drive did a good test a few years back....
Video - Fuel types compared - Drive
3min video, worth your time to watch if you are concerned about fuel ecomony.
Even though it was done back in 2008, fuel prices back then were pretty much the same as they are now (maybe even a tad higher)... so video is actually still 'in date'.

3 identical cars driven over 2,000km of city and hwy driving.
ok, there's the arguement that the 3 cars probably have tiny differences in fuel ecomony.... but this is still much more accurate than trying to drive the same car exactly the same way, pumping the same fuel batch, in the same weather and road conditions ... 3 times over. just not gunna happen, no matter how careful you are.

results? jack all in it really... but there IS a difference.
over 2000km, fuel use was:

Regular = 208.44L
E10 = 217.22L
Premium = 200.61

So you used less fuel with premium, but when you factor in the pump price difference, the fuel cost difference is:

$271.56
$276.55
$285.54

So in a nutshell= Regular Unleaded is the way to go.
E10 costs more to run (and probably gunks up the engine faster?), whilst Premium is the 'cleaner' fuel but will cost you more to use it (a little more than 5% above Regular actually).

Premium gets a little better if you use it in the city (becomes virtually identical to E10 in terms of cost), but Regular is still best.

 

[kato128]

I found the order to be regular unleaded followed by 95ron premium and then 98ron. I found ethanol fuels drank like a fish (e85) or ran so badly I had to floor it to get the car moving which hurt the economy (e10). The economy was roughly the same across all the non ethanol blends so it came down to price and how well the car ran on it

I think you'll find my testing is comparable since 4 tanks is roughly 2000km and since I used the same vehicle for each test there will be no engine differences.

Fuel batch differences are accounted for because of the extended time of the test. You're never guaranteed to get the same batch but any bad ones will average out over the month it takes to test each fuel type.

As for driving the same that is true but I think drive using 3 different drivers in their test would have more deviation than if only one driver was involved. I just drove as I normally would so a regular commute, a bit of town driving on weekends and after work, and an interstate trip each month. Sure it's not 100% consistent but I'm of the opinion that about 80% of it is which should give a reasonably accurate result. While it's not comparable to other peoples styles, the difference between fuels should be about the same even if someone else is driving in different conditions.

Also while it's nice to see drive etc doing this kind of thing it's not the same as hearing it from someone with no financial attachment to the result. I went into this with only the desire to find out which fuel would run the nicest for the cheapest price.

I do agree that regular unleaded seems to be the way to go and my data supports this. Now if the hippies here in Canberra would actually sell it at more than 2-3 servos then it'd be all good.

 

[UFO]

100% props to your efforts, I've enjoyed reading all your posts here. very thorough.
i did forget to mention in my summary of Drive's efforts that they did change drivers around the 3 cars too.

but mute point as we seem to be coming down to the same concensus anyway.... regular unleaded is the way to go. :beer chug:

 

[yxyx64]

Fair enough...so why do you think you are getting better economy on, in theory, lower octane fuels?

my off-hand thought is colder air temps as autumn/winter approaches. 91 should be cheaper but not give more miles than 98

I found the order to be regular unleaded followed by 95ron premium and then 98ron. I found ethanol fuels drank like a fish (e85) or ran so badly I had to floor it to get the car moving which hurt the economy (e10). The economy was roughly the same across all the non ethanol blends so it came down to price and how well the car ran on it...........................

E fuels have less energy content so you must experience a decrease in performance. Same for lpg. If your motor internals have been built for 91 octane then any other fuel is partly a compromise. You may get some benefits from say 98, but you are not getting the best bang for your buck without changing pistons. A slight fiddle with advance is not the same as upping the CR.

E fuels also have a different hydrocarbon ratio to petrol (and petrol also has a range of hydrocarbon ratios as batches, grade, manufacturer, time of year etc vary) so even though lambda is still 1 from O2 when on E85 the AFR tables need much adjusting when changing from petrol to E fuels and running in open loop conditions.

GMH spend big bucks so commodores will run on 91.