Author Topic: Non-branded supermarket petrols  (Read 1472 times)

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Martin

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Non-branded supermarket petrols
« on: 23 February, 2017, 12:26:53 »
As a non-engineer/mechanic, I'd greatly value the observations of experienced owners about supermarket petrols.

My BSA is an unmodified 1968 Lightning which has run happily on Co-op unleaded but, now that the local store has closed for good, I've been advised to go for branded fuels, and warned off Tesco unleaded on the grounds that it is likely to cause damage to combustion engines (!).

I realise from what I've researched that different additives are used wherever you go for fuel, and nobody knows what's in the stuff when you fill up, but can anyone tell me whether they've had problems with standard non-branded petrols from the major supermarkets?  Thanks in anticipation.

Arthur

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Re: Non-branded supermarket petrols
« Reply #1 on: 23 February, 2017, 14:23:42 »
Petrol sold by different outlets is not always the same and can vary greatly. Generally, premium unleaded is rated at 95 octane but not all versions produce the same performance in your engine. If you've got an engine which is more highly tuned then you may notice the differences more than other people. With super unleaded, the octane rating can vary more (97-99) and the difference in performance may be even greater. So if you notice any differences in your engine, its probably best to stick to known brands that suit your engine.

STAR TWIN

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Re: Non-branded supermarket petrols
« Reply #2 on: 23 February, 2017, 15:07:26 »
Supermarket fuel is generally considered to have a higher ethanol content than forecourt fuel and, due to the price war, a reduced amount of the additives that counter the effects of ethanol. Morrisons by word of mouth has a particularly poor reputation. Our local car repair business makes a strong point of warning customers off supermarket fuel.
One thing to bear in mind is that octane ratings are not measured in the same manner as they were when out bikes were new. You can as an approximation knock off a few points. So current 98 octane is about the same as the old 95 octane.
If you must use supermarket fuel, be kind to your carb and shut off the petrol before you stop and let the engine run out of fuel. That way should avoid the insidious corrosion caused by fuel/ethanol/water lurking therein. A splash of 2 stroke oil in the petrol won't do any harm.     

Martin

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Re: Non-branded supermarket petrols
« Reply #3 on: 24 February, 2017, 09:53:51 »
My thanks to you both for your helpful comments! Other than flushing the tank through with cleaning products to rid it of decades of rust and other muck, I haven't lined it against the effects of ethanol, so will take your advice and stick to the branded fuels.

Arthur

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Re: Non-branded supermarket petrols
« Reply #4 on: 24 February, 2017, 12:22:31 »
If you've got a steel petrol tank then at worst petrol will help keep it free of rust - it shouldn't have any detrimental effects whatsoever. However, if your 1968 Lightning is unmodified and hasn't had the valve seats converted for running unleaded fuel then this would be my main concern. Without conversion, the exhaust valve seats will suffer recession due to lack of the lubrication provided by the old leaded fuels. Modern fuels from different sources might well affect the rate of recession depending on what additives they contain.

STAR TWIN

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Re: Non-branded supermarket petrols
« Reply #5 on: 24 February, 2017, 14:38:59 »
The problem with ethanol in petrol is that it is hygroscopic. With moisture in the air being absorbed, you can end up with an ethanol/water mix lurking in the bottom of your petrol tank and hence corrosion. You certainly notice this in older Japanese bikes with tanks made from fairly thin steel. The sudden rise in new petrol tanks available from India gives a hint that this is affecting our old bikes too. As an aside, speaking to a heating engineer, I was told that nowadays 90% of his callouts are due to water contamination in heating oil. All started when ethanol started to be added...

Martin

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Re: Non-branded supermarket petrols
« Reply #6 on: 25 February, 2017, 15:02:19 »
Thanks again, folks.

What little information I have been able to glean about my bike's history is that the previous owner gave it a top-end overhaul as far as the piston rings when he thought decarbonization was necessary, and I imagine he would have examined and dealt with the valve seats at the time - or at least I hope he did! The mileage reading is still under 11,000, and there's plenty of poke in performance terms.

From what you advise, though, it seems there's something else I need to look into the next time the bike is off the road, as I'd never have given the valve seats a thought.

STAR TWIN

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Re: Non-branded supermarket petrols
« Reply #7 on: 25 February, 2017, 17:52:33 »
A65s have alloy heads with valve seat inserts which are hard enough to cope with unleaded petrol, so no worries there. There were lots of scare stories about valve seat recession in cast iron heads but actual cases are relatively uncommon. I've had no problems with my iron-headed B31, A7 and Land Rovers.

bikerbob

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Re: Non-branded supermarket petrols
« Reply #8 on: 25 February, 2017, 18:07:06 »
I wouldn't get to hung up about fuel if you take out the big players Esso and BP there are still a vast number of different forecourt names out there and to the best of my knowledge including the supermarkets none of them own a refinery so it stands to reason that that a good many of them will be getting their fuel from the same refinery. I do however think that the main concern is Ethanol at the moment it is between 5 and 7.5 percent maybe as high as 10 percent but I remember reading somewhere that if it went to 10 percent or higher under EU rules it has to be labelled on the pumps in America it is 15 percent.

Arthur

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Re: Non-branded supermarket petrols
« Reply #9 on: 25 February, 2017, 23:50:54 »
From what you advise, though, it seems there's something else I need to look into the next time the bike is off the road, as I'd never have given the valve seats a thought.
Fortunately, it is possible to detect if significant valve seat recession is occurring by monitoring the exhaust valve clearances. If recession is taking place, you'll find the clearances will decrease with time. A few thou won't matter but if you loose significantly more clearance than this over a few thousand miles then recession might be an issue.

Martin

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Re: Non-branded supermarket petrols
« Reply #10 on: 26 February, 2017, 09:56:59 »
I never cease to be amazed at the depth and breadth of knowledge within the Club so, once again, thank you all for your comments. They're extremely helpful to the likes of one who has had a gap-41 years between riding A65s, and clearly an awful lot has happened in that time!

The tip about checking valve clearances rather than digging deeper is appreciated, Arthur. Something else that, with no mechanical background, I wouldn't have thought about.

bikerbob

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Re: Non-branded supermarket petrols
« Reply #11 on: 26 February, 2017, 10:26:47 »
Arthur is correct about valve seat reccession but it is not something that happens quickly. When unleaded petrol came in I owned an A10 Gold Flash at the time and was concerned about the possible effect on the valve seats so having a spare head at the time I ran the bike without any additive for a year took the head off and checked there was no reccession, but I did start to use the additive Castrol valvoline and still do,not sure if it makes any difference but a bottle lasts me at least 2 years you only add 1ml per litre of petrol maybe I am being over cautious. The advised test at the time was to set your valve clearances then check at 500 miles then 1000 miles and finally at 1500 miles if no reduction in the clearances then your engine was OK to run on unleaded.  I only use the additive in my A7 because it has no seperate valve seats I do not use it in my A65 and in the last 5 years I have not noticed any problems.

JulianS

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Re: Non-branded supermarket petrols
« Reply #12 on: 26 February, 2017, 12:08:13 »
In the mid 1990s the publicity surrounding the introduction of unleaded was almost completely negative, resulting in high levels of anxiety for some of us. Fortunately most of the predicted problems have not happened. My own experience with C11, B25 B40 plus an iron head A10 and alloy head A10 has been that I suffered no apparent recession. Use included regular commuting to work on the A10s.

I suspect that we cause more recession ourselves by over zealous valve seat recutting and grinding.

Ethanol is a different issue, though it is not new in petrol. Remember Cleveland Discol petrol fro the 1950s and 1960s?

The problem I had was with the ethanol disolving the old tank sealer, forming a sticky varnish over carb slide which caused carb to stick open. Not nice.

Solution - strip old sealer and reseal with ethanol resistant.

The other issue was that the petrol tap corks shrank with ethanol fuel allowing fuel to seep.

Solution - new lever action taps.

« Last Edit: 26 February, 2017, 12:15:31 by JulianS »

Arthur

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Re: Non-branded supermarket petrols
« Reply #13 on: 26 February, 2017, 13:35:44 »
I've tended to go for the unleaded fuel conversion whenever I've had significant engine machining done (re-bore, plain bearing reaming, replacement valve guides, etc) because the cost of replacing the exhaust valve seats at the same time is a small percentage of the total. That said, I've never seen much evidence of valve seat recession even on my A10 iron head which had done a fair old mileage before I restored it.

Trev

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Re: Non-branded supermarket petrols
« Reply #14 on: 26 February, 2017, 16:46:38 »
Quote
The problem I had was with the ethanol disolving the old tank sealer, forming a sticky varnish over carb slide which caused carb to stick open. Not nice. Solution - strip old sealer and reseal with ethanol resistant.
Ethanol resistant sealer? Ethanol proof I would suggest is more satisfactory. Ethanol resistant would not protect the sealant indefinately. The problem is how do you define resistant? OK for current ethanol levels? But what about future increases in ethanol percentages? Sadly there is no turning back the clock. The genie is out of the bottle now.