Fuel

UK forum for general and technical discussion about the Z3 roadster
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corky
Joined: Fri 27 Nov, 2009 18:09
Posts: 265

  M roadster S50
Location: Wakefield

Fuel

Post by corky »

Ok guys can anyone settle an argument,
I have a 1999 Z3 M and have been told that I have to put lead adative in the fuel because it will damage the valve seats if I don't
Can anyone advise and settle argument

Regards corky :!:
Mugs
Joined: Wed 07 Aug, 2013 01:26
Posts: 341

  Z3 roadster 1.9

Re: Fuel

Post by Mugs »

i think that that only applies to much older cars before the first of the Z3s were even made that were designed to run on 4 star leaded fuel. i believe all zeds were designed to run unleaded fuel.
Brian4
Joined: Mon 19 Dec, 2011 19:02
Posts: 541

  Z3 roadster 3.0i
Location: Hinckley

Re: Fuel

Post by Brian4 »

I think it was all cars made after 1992 had to run on unleaded fuel. Leaded fuel was withdrawn from sale in 2000 and was hard to find before then. The BMW engines of hat era were designed to run on unleaded. It could be that the person telling you could be confusing with the higher octane fuel reccommended for the M engines super unleaded Vpower etc.
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therealdb1
Joined: Tue 25 Jun, 2013 21:47
Posts: 263

  Z3 roadster 2.0

Re: Fuel

Post by therealdb1 »

Absolute nonsense, Corky!
Mugs is correct.
If you put lead in the tank you will probably destroy your catalytic converter.
What the guy is talking about is that you should use high octane fuel in other words 'super unleaded' RON 95 or above if you can find it not the usual rep-mobile supermarket unleaded.
In fact there have been lots of reports on here that suggest Z3's of all engine sizes seem to run better on super unleaded after a couple of refills. I'm trying mine now on its second tankful but the jury is still out at present.
They say that a little knowledge is a dangerous thing!

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Robert T
Site Admin
Joined: Mon 12 Jun, 2006 10:35
Posts: 10170

  Z3 roadster 1.9
Location: Cheshire

Re: Fuel

Post by Robert T »

I don't even put lead additive into the Sprite! Okay, so it has been fitted with an unleaded head, but it really isn't something you would expect to do on a modern car.

The Z3 (no matter what engine size) was designed for unleaded, and as stated, lead (or lead additive) would ruin the cat.

The suggestion that the ///M engines require higher octane fuel (i.e. super-unleaded) is correct - there should be a label on the fuel filler cap suggesting such. The non-///M engines will tolerate lower octane fuel (i.e. ordinary unleaded), but they all (even the 1.9) seem to run far better on super.

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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Mike Fishwick
Joined: Fri 19 Jun, 2009 10:27
Posts: 2093

  Z3 roadster 2.8
Location: Daglan, France

Re: Fuel

Post by Mike Fishwick »

A lot of M owners try to tell people that their mighty engine is the only one which needs high octane fuel, due to its enormously high compression ratio, which is not much higher than 2.8 anyway.

Like most BMW engines, the M engines do not 'require' a high-octane fuel, but are optimised for it, and will therefore run better on it. This consideration applies to the 1.9 140 bhp engine too - which is rated at this power level on 95 octane, but as the handbook states, will produce more on higher-octane fuels.

The M engine will tolerate lower octane fuel, but will obviously produce less output, such as 280 bhp on 95 octane - if you can find a UK 95 as good as that used in 1998 by BMW when they tested the early engines - which was free of ethanol, benzene, and other dilutants now used. Most rolling road tests on UK fuel often find that an M engine can produce only about 230-250 bhp, due mainly to the poor quality of most UK 97 octane petrol.

In spite of many owners being obsessed by their engine's fabled 231 bhp, there are several other reasons why they usually fail to produce this power - as if every engine produced the same output, to a tolerance of 1 bhp . . . .
Last edited by Mike Fishwick on Wed 19 Aug, 2015 09:57, edited 2 times in total.
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Fuel

Post by Southernboy »

If you want to add anything - add a reputable brand of octane booster. Never add lead replacement. :rtm:
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Simon59
Joined: Thu 06 Nov, 2014 13:17
Posts: 30

  Z3 roadster 1.9
Location: Wilmslow

Re: Fuel

Post by Simon59 »

I've been using Shell V-Power Nitro+ (unleaded of course) in my 1999 1.9 and I swear it's getting better and better with each tank full! :D
Hairyscreech
Joined: Thu 16 Apr, 2015 12:08
Posts: 69

  Z3 roadster 2.8

Re: Fuel

Post by Hairyscreech »

Yikes, BMWs have had hardened valve seats since at least the 3200 of the early 60s. Germany have had unleaded fuel for a lot longer than we have.

No modern BMW will need leaded fuel and certainly no car with an aluminium head.

The whole leaded fuel for old cars comes from cheap old cast iron heads on fords etc that did not have hardened valve seats and the valve seat was cut into the cast iron.
Mike Fishwick
Joined: Fri 19 Jun, 2009 10:27
Posts: 2093

  Z3 roadster 2.8
Location: Daglan, France

Re: Fuel

Post by Mike Fishwick »

Yes, it is hysteria from the so-called 'Classic' car brigade. Any engine with valve seats machined directly in a cast iron head is a problem, but one with seperate valve seat inserts is fine. Even with old engines such as this, the seat's sealing area has become work-hardened with use, and also absorbed a lot of lead from the fuel, so as long as the seats are not reground/cut they are usually fine with unleaded fuel.

If the seats do begin to wear, all that will happen is that the valve clearances will reduce, which is easy to detect, and may begin to burn - but when the seats are replaced there is no other damage done, so you may as well leave things alone and see what happens. With the low rate of use such cars get an old seat will last a long time.

Some people have found that after having new seats fitted the new ones come loose in the head, which is a real nuisance - and which could have been avoided by leaving well alone.

A decent octane booster/cleaner such as Millers Power-Plus is always a good idea, as it not only boosts the quality of modern fuel, but also removes the carbon build-up one frequently sees on injector nozzles. One £15 bottle lasts for about 5000 miles.
A Z3 is not just for Christmas - it's for life!
littlefeller
Joined: Sun 28 Apr, 2013 18:06
Posts: 683

  blank

Re: Fuel

Post by littlefeller »

someones pulling your leg, right that's it - get the wickerman out, not had a good burn-up for ages :lol:
Mugs
Joined: Wed 07 Aug, 2013 01:26
Posts: 341

  Z3 roadster 1.9

Re: Fuel

Post by Mugs »

Simon59 wrote:I've been using Shell V-Power Nitro+ (unleaded of course) in my 1999 1.9 and I swear it's getting better and better with each tank full! :D
+1
i've been using it in my 1.9 for the past few months and its now smoother and has better throttle response. this has happened over a few fill ups and the difference isn't apparent until about tank 5 or 6 and then it just starts to feel better every tank full.
corky
Joined: Fri 27 Nov, 2009 18:09
Posts: 265

  M roadster S50
Location: Wakefield

Re: Fuel

Post by corky »

Cheers guys I think that you have answered all my questions regarding the fuel,
I will now bet on a few pints of the amber Nector and then let him read all your replys I should be able to live on this for a few weeks

Regards corky :cheers
littlefeller
Joined: Sun 28 Apr, 2013 18:06
Posts: 683

  blank

Re: Fuel

Post by littlefeller »

Mugs wrote:
Simon59 wrote:I've been using Shell V-Power Nitro+ (unleaded of course) in my 1999 1.9 and I swear it's getting better and better with each tank full! :D
+1
i've been using it in my 1.9 for the past few months and its now smoother and has better throttle response. this has happened over a few fill ups and the difference isn't apparent until about tank 5 or 6 and then it just starts to feel better every tank full.
this may have something to do with the fact your ecu will learn over a period of time. not all ecus are like this, I remember a car I once owned (showing my age, xr4i) on this car if I disconnected the battery then reconnect the car was a lot more responsive and seemed to have more power for a while, after about 20 miles it would return to normal, some ecus use a knock sensor and will advance timing till knock then err on the safe side, these learn very quickly ( usually on jap high performance cars). personally I have never used high octane on my m44 simply because there is a morrisons petrol station just 200 yards from where I live :( (I'm lazy)
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pingu
Joined: Fri 30 Apr, 2004 16:01
Posts: 3412

  M roadster S50

Re: Fuel

Post by pingu »

littlefeller wrote:... because there is a morrisons petrol station just 200 yards from where I live :( (I'm lazy)
I hope their petrol is better than their diesel.
Pingu
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Robert T
Site Admin
Joined: Mon 12 Jun, 2006 10:35
Posts: 10170

  Z3 roadster 1.9
Location: Cheshire

Re: Fuel

Post by Robert T »

Owner's Manual (UK Pre-facelift) wrote:Engine with catalytic converter
The engine should be run exclusively on unleaded fuel. Since the engines have a knock control function, they can run on different grades of fuel.

Z3 roadster 1.8/2.8, Z3 coupe 2.8, M coupe, M roadster:

The BMW engine is designed to run on:
  • Super Plus unleaded (octane number 98 RON).
Try to use this fuel whenever possible, so the car achieves its specified performance and fuel consumption.
You can also use the following fuel:
  • Premium-grade unleaded fuel (octane number 95 RON).
This fuel is also known as DIN EN 228 or Euro Super.
The minimum permitted fuel grade is:
  • Regular-grade unleaded fuel (octane number 91 RON).
In view of the engine's requirements, use this fuel only in exceptional circumstances.

Z3 roadster 1.9:
Minimum fuel grade:
  • Regular-grade unleaded fuel (octane number 91 RON).
The rated performance and fuel consumption values can be achieved with:
  • Super unleaded (95 octane RON).
This fuel is also known as DIN EN 228 or Euro Super.
For higher performance and lower fuel consumption, it is also possible to use
  • Super Plus unleaded (octane number 98 RON).
** Never use fuel containing lead if the car is equipped with a catalytic converter, or the oxygen sensor (lambda probe) and the converter will be damaged beyond repair.
And to prove that I had actually read that ///M's should not be run on ordinary unleaded, here is what the 2000 US manual had to say:
Owner's Manual (US 2000) wrote:Z3 roadster, Z3 coupe
The engine uses lead-free gasoline only. However, you can refuel with different fuel qualities since the engine is equipped with a knock sensor. In order to achieve rated values for engine
performance and fuel consumption:
  • Super lead-free premium gasoline (91 AKI).
The minimum fuel quality is:
  • Regular lead-free gasoline (87 AKI)
  • Because of the engine's design, you should refuel with this gasoline only as an exception.
M roadster, M coupe
The engine uses lead-free gasoline only. However, you can refuel with different fuel qualities since the engine is equipped with a knock sensor. In order to achieve rated values for engine performance and fuel consumption:
  • Super lead-free premium gasoline (91 AKI).
The minimum fuel quality is:
  • Lead-free premium gasoline (89 AKI)
  • Because of the engine's design, you should refuel with this gasoline only as an exception.
** Do not use leaded fuels. The use of leaded fuels will cause permanent damage to the system's oxygen sensor and the catalytic convertor.
So I take that to mean that the fuel consumption figures for the 2.8 and ///M were done on super unleaded, whilst those for the 1.9 were on ordinary unleaded. I am ignoring the 1.8, as I don't think this was ever sold in the UK - this is a genuine 1800cc engine and not the facelift 1900cc engine.

Based on that, I would still say to only run an ///M engine on super unleaded (98 RON).

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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Mike Fishwick
Joined: Fri 19 Jun, 2009 10:27
Posts: 2093

  Z3 roadster 2.8
Location: Daglan, France

Re: Fuel

Post by Mike Fishwick »

AKI - the Anti-Knock Index - is a rating used in the US and Canada, being the average of the Research and Engine Octane Numbers. It is usually about 5 numbers less that the corresponding octane number used in Europe, so 91 AKI fuel would be our 95 octane, which is used by most M owners in the UK, in the absence of anything better - in the south-west for example, even V-Power is not available everywhere, and I have never been impressed by that anyway.

While the engine will not be harmed by its use, output is a lot lower, and the makeup of the fuels usually leaves a lot more carbon in the engine, particularly on the back of the inlet valves, so upsetting the air flow into the cylinder. This is just one of the reasons why the M engineusually fails to produce its fabled 321 bhp, although what is left is more than enough to frighten most people!
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Hairyscreech
Joined: Thu 16 Apr, 2015 12:08
Posts: 69

  Z3 roadster 2.8

Re: Fuel

Post by Hairyscreech »

Its also worth noting I think all of the Z3 engines have knock sensing, It was introduced with the E36 M50B25TU and the E36 M43B19. So no need to worry about detonation.
Tilly
Joined: Wed 26 May, 2004 19:45
Posts: 439

  M roadster S50
Location: Sussex

Re: Fuel

Post by Tilly »

Owning both a 1.9 and M for over 15 years, we have tested both cars on Shell 95 and V -Max refilling several times to let the ECU acclimatise. Could we detect a difference in performance between the fuels in each car. Frankly no. What did we decide to do. We run the 1.9 on 95 and the M on V-max. Why, since I we cannot detect a difference. In the end we have followed BMWs recommendation in the handbooks. I trust that their engineers know best.
Mugs
Joined: Wed 07 Aug, 2013 01:26
Posts: 341

  Z3 roadster 1.9

Re: Fuel

Post by Mugs »

Just to prove a point, my Impreza was mapped on high octane at 285BHP / 330lbft torque.
i went on a rolling road day with the subaru club a few weeks later (just to join in the fun) and had to use 95 ron as my local shell was being re-stocked with fuel. it only produced 270 / 320lbft so went back a couple of weeks later as i thought something was wrong, this time back on v-power, and it was 286 / 329lbft so there must be something good in it.
therealdb1
Joined: Tue 25 Jun, 2013 21:47
Posts: 263

  Z3 roadster 2.0

Re: Fuel

Post by therealdb1 »

I'm not saying that the fuel had no effect but you also need to take into account the ambient temperature, pressure and humidity especially since your tests were several weeks apart.
Cold air will be more dense and therefore have more mass for the same swept volume. Since cars these days have a Mass Air Flow meter (MAF) on the inlet the engine will know this and inject more fuel producing more power.
The water content of the air will also have an effect as will to a small degree the pressure on the day. Even with a turbo if the air ain't there in the first place it cannot compress it.

As Hairyscreech says knock sensors have been common fitment on a majority of engines for many years. My 6 pot has two amusingly titled "ping" sensors fitted one for the front 3 cylinders and another for the rear 3. In the UK we usually call the effect of pre-ignition "pinking" although I guess "pinging" is equally onomatopoeic so maybe all is not lost in the translation from German!

Provided the sensors and ECU are functioning correctly then you will not get knock, pinking or pinging as long gone are the heady days of rotating the distributor with a stroboscope attached wondering if that really is the 5 degrees before top dead centre mark you are looking at!
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