Fifth Gear Unleaded/Super Unleaded Experiment

[samm_cvr6 0]

I think you do notice the difference when you are driving the card hard,, and of course it does idle better. But one thing I am also certain of is the car returns a higher mpg with Optimax, and I have tested this countless times.. I get about 3mpg minimum more with Optimax, so the 5p a litre more is a more then worth it in my opinion..

[Walesy 0]

I think the " you are what you eat " comment is a good one, that's the way I look at it. I get laughed at for putting Evian instead of tap water in my car but I do that using the same theory.

[Andy T 0]

I get laughed at for putting Evian instead of tap water in my car

 

:lol: why mineral water? wouldnt Distilled/De-ionised water be better?!

[dazzyvr6 0]

http://www.theaa.com/routeplanner/advertorial/ interesting read

[Walesy 0]

LOL..yeah, but I never have any, but I do constantly have bottled water (( wifey's a health freak )) so instead of using tap water i'll use mineral. :D

[The Leningrad Cowboy 0]

http://www.theaa.com/routeplanner/advertorial/ interesting read

 

That's hilarious! It's a while since I've read any sort of bumpf where they quote seemingly random numbers to get you interested, without actually justifying where any of them came from. Come to think of it, the last time was probably something the government was trying to sell.

 

Lies, damned lies, and statistics...

[craigowl 0]

I would not use mineral water in the cooling system.

I believe we have to use distilled water because there are no minerals in it!

Bottled mineral water, I am certain, contains more calcium, etc, than, say, the soft water out of many of our taps in Scotland, at least.

Having said that, it may take years to cause a problem, I do not really know what part modern coolants like G12+, etc, play in the equation.

A few decades ago, though, hard tap water, etc was strictly taboo in the cooling system. We are all at the mercy of the scientists working for the oil/coolant/fuel companies here. Very few consumers will get to know what really matters, I suppose.

[Walesy 0]

I would not use mineral water in the cooling system.

I believe we have to use distilled water because there are no minerals in it!

Bottled mineral water, I am certain, contains more calcium, etc, than, say, the soft water out of many of our taps in Scotland, at least.

Having said that, it may take years to cause a problem, I do not really know what part modern coolants like G12+, etc, play in the equation.

A few decades ago, though, hard tap water, etc was strictly taboo in the cooling system. We are all at the mercy of the scientists working for the oil/coolant/fuel companies here. Very few consumers will get to know what really matters, I suppose.

 

:oops: LOL, I can remember being told that using tap water is bad, so like I said, I used the " you are what you eat " theory and used bottled water... :oops:

[Unclebuck 0]

I wish I'd seen the program.

A few years ago I worked for a company that gave me a petrol card. I had to prove to the Financial Director by supplying a photocopy of the (at that time G60) instruction manual, that I should be allowed to buy RON98 fuel.

The manual says:

16V - not lower than RON95

G60 - not lower than RON95. For prolonged high speed driving at high ambient temperatures, RON98 should be used.

VR6 - RON98. BUT: The use of RON not less than 95 is possible without restrictions. Automatic adaption of ignition timing to fuel quality can during unfavourable conditions cause slight loss of performance. This can be partly compensated for by using RON98.

(What a weird statement).

 

I really wanted to know how supermarket super-unleaded stacks up.

[ZippyVR6 0]

I use the Reverse osmosis water I use on my fish tank. It has no minerals and is basicly just pure H2O. a 50 litre drum is only 3,50 from my local fish shop.

[Kevin Bacon 5]

Tap water is fine. Coolant additive contains water conditioners aswell as the Glycol. Do you lot seriously think car service centres use anything other than tap water in engines?

 

98 RON - Yep it makes a difference and I can show you the difference using the VAG-COM knock table measuring blocks. It's the people that don't give a sh1t about their cars who generally put crap fuel in them....

[Walesy 0]

Tap water is fine. Coolant additive contains water conditioners aswell as the Glycol. Do you lot seriously think car service centres use anything other than tap water in engines?

 

98 RON - Yep it makes a difference and I can show you the difference using the VAG-COM knock table measuring blocks. It's the people that don't give a s**t about their cars who generally put crap fuel in them....

 

 

:lol: LOL...you're in a good mood today Kev :wink:

 

 

Tis true though...I would put any old p1ss in my taxi's when I had them...but every raddo I had I never put anything but super. Horses for courses. :D

[Kevin Bacon 5]

LOL, you always crack me up Walesy :-)

 

No I thought I'd try the BCStudent and Dr Mat emotionless style of posting :-)

 

It does make you sound stroppy doesn't it?! ;-)

 

That comment was actually inspired by the great Student actually..... he has a nice Corrado, in gleaming black and two comments I've read today about it where "I clean it 3 times a year" and "I use the cheapest, shittiest petrol I can find"......well, if that's how he treats a Rado.....one does wonder why he's a member of an Rado 'appreciation' society....

[The Leningrad Cowboy 0]

OK, please correct me if I'm wrong. But the TV 'blindfold' test was 95, 97 and 98 RON. And then they tested it for power with engines designed / mapped to run with different levels of RON in their fuel. Well, blow me if the engines actually produced most power when using the RON they were designed for.

 

A higher RON does not equal more power. RON does not correlate to the energy available in the fuel. RON is a measure of the energy level at which premature detonation happens (knocking). A higher RON therefore means that you can put more energy into the fuel without it combusting prematurely (equating directly to the compression ratio at which you can run). This is why performance engines are designed to run with higher RON - they can run at a higher compression ratio. However, just putting higher RON in than your car is designed for doesn't change the compression ratio that the engine mechanism is designed around, so you won't get more power. I think you would be wasting your money putting in a RON higher than the manufacturer's recommendation.

 

Now, as far as knock goes, I fully suspect that a supermarket fuel is as good as a 'branded' fuel, as the RON is objectively defined the same (we have to rely on the DoT for that, of course). So there should be no advantage in using a branded 97 of Tesco 97 from an anti-knock point of view. This doesn't mean, of course, that there aren't other reasons for buying branded, but these wouldn't be so obvious, as they are more subjectively understood by the public through advertising.

 

As I said, please correct me if I'm wrong - I'm certainly no expert, and have just followed what I see as a logical train of thought.

 

Cheers.

[Walesy 0]

..Yeah I can see your logic, but following that same line of thought surly a car that states " Use 98 RON " on the petrol flap would make the car run less effectivly when using lower RON fuel...like I've said before ..my raddo idoled slightly more lumpy the one time I used 95 RON (( when i first bought it )) so I didnt use it again.

 

Not suggesting that if i put super unleaded in my 750cc fiat it's gonna make it go like a rocket, but if you have a car designed for use with super then it's better to do so in my un-educated opinion :wink: .

[The Leningrad Cowboy 0]

I think you're agreeing with me, which gives me a bit more confidence. The 95 in the VR6 would mean that the engine cannot run at the design point compression ratio due to premature knocking. The knock sensors will obviously pick this up and adjust the timing to compensate (retard or advance, I'm not clever enough to know), but it will run unevenly, and not at the optimum compression ratio (so less power). So, that fits, I think! Yes, based on my line of thought, put whatever RON in the VR that VW recommend, and likewise for all other cars!

[Kevin Bacon 5]

I found my VR (when standard) felt slightly torquier with Shell 95 than Optimax, low down....but past 4000rpm the drop in acceleration was noticable, which is where Optimax did it's best work.

 

I can't use 95 now it's charged, well, I could but the knock retardation at 6000rpm would be 10 degrees instead of between 6 and 8 I get now with Optimax. You can monitor all 4 knock channels with VAG-COM (OBD2 only I'm afraid :-( ) and it's usually the rear bank that knocks the most as it runs the hottest. So it's a VR owners best interests to relax the sensors as much as possible by using Optimax.

 

I even tried some of that Tesco 99 stuff but tbh, I didn't 'feel' any difference over Optimax and still got the same 6-8 deg knock at 6000 WOT.

 

I think Shell V power (if it ever arrives) might knock a degree or two off that, hopefully. With Aquamist, the knock should stay at 0 through the range :-)

[davidwort 0]

..Yeah I can see your logic, but following that same line of thought surly a car that states " Use 98 RON " on the petrol flap would make the car run less effectivly when using lower RON fuel...like I've said before ..my raddo idoled slightly more lumpy the one time I used 95 RON (( when i first bought it )) so I didnt use it again.

 

Not suggesting that if i put super unleaded in my 750cc fiat it's gonna make it go like a rocket, but if you have a car designed for use with super then it's better to do so in my opinion.

 

Optimax in my 16v allowed it to be set to just over 8 degrees of advance at idle and increased the power by almost 10 bhp over it being set closer to the 6 degrees manufacturers setting, that was back to back on Stealths rollers a few weeks ago.

I know that is on a simple KR ignition map with no knock sensores etc.. but that suggests to me that a car with an adaptive ECU or agressive advance map can make quite a bit more power on higher octane fuel.

Not sure how the VR6 or Digifant systems cope with different fuel but I suspect they are mapped for a particular grade eg 98RON (with a bit of margin for safety) and then simply knock back the timing if the fuel grade is worse, i.e. without a remap you won't get the most from optimax but it should develop more power than filling with 95.

 

David.

[Walesy 0]

I think you're agreeing with me, which gives me a bit more confidence. The 95 in the VR6 would mean that the engine cannot run at the design point compression ratio due to premature knocking. The knock sensors will obviously pick this up and adjust the timing to compensate (retard or advance, I'm not clever enough to know), but it will run unevenly, and not at the optimum compression ratio (so less power). So, that fits, I think! Yes, based on my line of thought, put whatever RON in the VR that VW recommend, and likewise for all other cars!

 

Yep deffo agreeing :D

[dinkus 10]

My thinking is that the extra RON doesn't make a huge difference. It'll burn cleaner and cooler than the lower stuff, but I don't feel it making a 4p/litre difference over the 95 stuff.

 

Having said that, I do try to avoid using supermarket fuel wherver possible. It's sometimes not possible, because it's a good 15 min drive to the nearest 'real' petrol station, but I usually get Shell stuff.

 

If I had money to burn, then I'd probably use super all the time, but especially at the moment, I just can't justify the extra £4 or so a tank just to line the pockets of the petro companies further.

[DelMonty 0]

I'm no expert, but from what I understand the higher RON allows for greater compression by the piston, so by allowing ignition nearer the top of the stroke, more power can be derived from the mixtue on the ignition down stroke.

 

Cars that have premature timing, are losing a considerable percentage of power, as well as causing engine damage through 'pinking', something a lot of older cars (cars without adaptive engine management) can suffer from.

[Jim 1]

As a random side note but vaguely on topic, BP Ultimate Diesel is an absolute wonder! The car feels more punchier, but one huge improvement is a total LACK of smoke when compared to supermarket fuels!

 

When pulling away from anyone at lights at night, driving with anything other than VERY light application of the throttle I was used to leaving people in a cloud of soot. But this Ultimate stuff just makes a difference like night and day! Barely any smoke at all! Will make sure I give it a tank or two full before I go for my MOT / emissions tests!! :)

[NickVR6 0]

I remember an article in one of the car mags a few years back where they ran 3 brand new cars on 95. They took the engines apart and phtographed the valves and piston tops etc. They then cleaned them and ran them on optimax for the same 4000 miles againa dn took them apart.

 

Must have been an expensive test, using 3 diff cars i can only remember one was a 321bhp m3 engine.

 

Cut a long story short, 95 was noticeably coked up but after the Optimax they all looked bling tasticly clean and shiney!! I've never used anythign else since. Apart from when i went to my last stealth run i got caught short and had to stick 95 in doohhhh! Made me even more chuffed with my figures though!

 

I do wonder if that amount of cleaning will affect the oil coating on bore surfaces etc though ? ? ? ?

[Musicman 0]

I've never felt more power from higher octane fuel, just a less lumpy idol.

 

????

[ZippyVR6 0]

Jim, I have a friend who works in the petrol tank business and he swears that BP ultimate diesel is the same as regular but with added vegetable oil. Buses in Reading have been running on the stuff for years as a test.

 

It does seem to work though, I used to use it in my oil burner 306 and it cut down the white smoke on startup? strange but true.