It's physically impossible to do 136mpg in a Prius. It's just not possible.

55mpg is probably a realistic max, people buy those cars just to one-up people, so they can say (I'm saving the enviroment), when in actual fact a Diesel Polo will do 70mpg!

This is a waste of time. You have two variables in this experiment - the fuel and your driving. Unless you do excactly the same route in the same conditions at the same speed etc etc then it's pointless, especially having so little data make comparison.

Quote from Storm_Cloud :

This is a waste of time. You have two variables in this experiment - the fuel and your driving. Unless you do excactly the same route in the same conditions at the same speed etc etc then it's pointless, especially having so little data make comparison.

There's more factors than fuel and driving. In my line of work I drive about 1000km to 3000km per month, during the fall months when I don't need A/C nor the engine/me need the Weber (extra engine/me heather) I can do ~700km/per tank, during the winter when I need the Weber during driving and the engine(/(me) needs it to be running for half an hour before start in the mornings, I do about 550km per tank.

Besides that, there's a factor what one calls "a tank" it depends on, is your car on a up or a downhill when filling up .

I do infinite miles per gallon when I walk.

If i am walking normally i am much the same. However, if im on a pub crawl, i am very un-economical, as i usually only manage up to one mile per pint.

Ehh. Walking is for the feeble.

Real men catch a cab.

Quote from S14 DRIFT :

Real men catch the crabs.

Anyway, if your car is supposed to take 87 octane, then put 87 octane in it... If your engine is knocking you have other issues.

Funny how so many people have started clinging to the octane number as anything to do with this thread. It isn't. Ignore octane (most of you haven't got a clue what it does or how it does it anyway), and concentrate solely on the other aspects of gasoline and its additives.

Quote from tristancliffe :

and concentrate solely on the other aspects of gasoline and its additives.

Yes, I understand that octane has nothing to do with the quality of the fuel. But it's not like manufactures list the specific additives. How can you be sure that one gasoline is higher quality then another? Without having access to a list of all the additives in the fuel. So, this is really a non-issue.

Quote from Riders Motion :

I do infinite miles per gallon when I walk.

I'd love to walk 7 miles to School, and then 20 miles to work - but I cba :P

Quote from wheel4hummer :

Yes, I understand that octane has nothing to do with the quality of the fuel. But it's not like manufactures list the specific additives. How can you be sure that one gasoline is higher quality then another? Without having access to a list of all the additives in the fuel. So, this is really a non-issue.

There are specification sheets and information about most premium fuels available with a quick search.

Having to remap a car for a change in fuel is bollocks, road car ECUs are designed to take whatever rubbish Americans throw in their cars to BP Ultimate and anything in between the ECU is capable of adjusting itself to cope and take advantage of whatever fuel has been put in.

Even race ECUs that are properly mapped (rather than the typical rubbish mapping produced by people who don't know what they're doing) with a specific fuel will still take different fuels without too big an issue most of our cars run guaranteed oxygen content 99 octane race fuel, which is very different from super unleaded fuels in terms of quality. They tend to get mapped on this but run 102 octane high oxygen content race fuel at times (it is the control fuel for the Silverstone 24 hour), otherwise it is whatever the customers want/provide, some of which looks suspiciously like pump fuel of some description in jerry cans! Only the 109 octane very high oxygen content rocket fuel requires a remap to run the fuel, it also requires an engine rebuild to make any sense of using the special fuel/safely run lower octane fuels again.

Quote from Forbin :

The idea that "more expensive fuels cost less in the long run" is a load of crap. Just buy the cheapest fuel you can get with the recommended octane rating for your engine and you'll be fine.

Now this is an extremely silly statement, the last time I checked internal combustion engines worked by igniting a fuel, the composition of which is obviously going to be critical to how said device works.

Quote :

(...) In terms of fuel economy, being able to advance the spark at full load certainly gives better economy, since the engine is making more efficient use of the energy in the fuel.

(...) However, knock isn't an issue at part load, where the engine spends most of its time. In terms of overall "real world" fuel economy benefit due to increased octane rating, the effect is likely to be small unless you drive much of the time at high load - either because you have an "enthusiastic" driving style, or because you have a relatively large, heavy car with a relatively small but powerful (typically turbocharged) engine. (...)

Quote :

(...)An additional advantage is that, due to their different composition, "premium" fuels are typically two or three percent more dense than "normal" fuel, which means that each litre contains two or three percent more mass of fuel, and hence two or three percent more energy. (...)

Problem is, their price is much more than 2-3% higher than standard. Conclusions:

Quote :

• if your manual specifically recommends use of high octane fuel, and particularly if you have a small turbo engine in a large vehicle, "premium" petrol should be used whenever possible
  
• if your manual recommends "ordinary" fuel but your engine has knock sensors, use of "premium" petrol on occasion may be worthwhile
  
• otherwise, it is hard to justify unless you particularly feel your engine needs additional cleaning (though in the US, I would be very tempted to stick to "Top Tier" gasoline to be on the safe side
  

Quote from ajp71 :

There are specification sheets and information about most premium fuels available with a quick search.

My search yielded no great detail. Like, no specific chemicals, etc. As long as the fuel meets the ASTM standards, I don't see any large advantage personally. Unless there's clear cut evidence that a specific fuel is better.

EDIT: I filled up my car with gas. 8 Gallons of premium. That means there was 4 gallons of regular gasoline left. Both are winter blends, presumably. So, I'll see if I notice any differences. Usually I average about 22mpg US (26mpg over there in the UK and wherever else uses imperial gallons), and that's 100% city driving. If I do half highway, half city, then I get like 28mpg US or so. I have gotten 36mpg at one point before, but that was literally all highway.

Quote from BAMBO :

you won't see any great improvement if you use Ultimate instead of normal, it should be just 1-2% so it isn't worth it.

Quote from S14 DRIFT :

Jack, how many threads till you realise you have a silly car that won't do meaningful amounts more mileage on a tank? I've tried this with my old RS, using Super Unleaded I'd get about 95 miles before the light came on, with normal it'd be around 90. 5 miles wow! Surely that's worth the extra £4 it cost to fill up when I had it
Honestly, if you're whinging about the fuel costs, how it's hard to afford etc, just stick with the cheap and cheerful fuel.. :doh:

Quote from S14 DRIFT :

The best fuel for you is regular 95. Now stop making a big deal of nothing, go back to scamming your insurance company or something.

Ok, heres my data (so far):



Now show me yours that made all those "informed" posts?

Am i reading it right? or does it say it cost you £1 per mile to run

More like 10p per mile.

But what we've seen here is it's still cheaper overall to use cheaper stuff at the pump. I'm at home atm Jack so I'll dig out the EVO article.

200 miles isn't enough. You'd have to do at least 2000 miles. Only problem, is that the additives could clean the engine better or worse depending on the gas. There's no way you can compare fuels without going a set distance on cars that are EXACTLY the same. You'd have to get 5 identical brand new cars and test it over the duration of several thousand miles.

Nice Jack, although a few things come to mind.

You are getting completely different average MPG so straight away it's an "unfair" test.

As for cleaning, I'll use High octane on my bike occasionally as it just feels more getup and go. Although if I really wanted to clean the injectors out I'd use an additive designed for doing exactly that.

But yeah, my experience of super unleaded on my old RS was back when unleaded was £1.02 and super was £1.12+. On my Z I tend to just use Super unless I'm on a budget.

Doesnt mean a jot Jak, especially when you see that 2 tanks fulls of Shell ordinary vary by 4 mpg!!!!!, and you get/got 6 mpg less on Shell V-power.

All that pic reinforces is that any kind of data you get from this type of test is useless due to varying factors.

Quote from danowat :

Doesnt mean a jot Jak, especially when you see that 2 tanks fulls of Shell ordinary vary by 4 mpg!!!!!

One was with underinflated tyres (20 something) versus correct tyres (30 *insertunithere*).

My car didn't seem to like V-Power, though - Although it was noticeably better with Shell (i.e. usually the "half way point" on the tank is reached at 150 miles (yeah my fuel indicator sucks) on Tesco petrol (Ultimate, which i used for about 5 weeks consecutively before I started this test) whereas it'd do 160-170 on Shell...)

On the 2 runs I measured with Tesco Ultimate, I got 36.2 and 36.1 MPG - I'd say that's a pretty close spread of results tbh.

Quote from S14 DRIFT :

As for cleaning, I'll use High octane on my bike occasionally as it just feels more getup and go.

Honestly couldn't "feel" a difference between any fuel (although V-Power didn't seem so good), however if all is the same i'd rather use expensive fuel (if the total cost is the same) because not only should it clean out my engine (which I doubt but meh) but more importantly the rewards are better (i.e. more reward points).

Oh you have these fuel loyalty points? I just use mah NECTARRRRR (lazar?) card because there's always a BP or a Sainsburys (prefer Sainsburys as it's cheaper!) about. Maybe I can feel a difference more than a car since I have am much more as one.

That said, 160 miles on half a tank is something I can only dream of! I bottled at 168.2 miles on a tank of standard 95.

My fuel tank is about 30-35L though...

I have a Shell Drivers Club Reward Card & A Clubcard - May as well get something back from giving them money (yes I know there is very little real reward - but every little helps...)

Quote from Jakg :

One was with underinflated tyres (20 something) versus correct tyres (30 *insertunithere*).

psi, I'd presume

Well it's not BAR is it.