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MG MGB Technical - Supermarket Petrol

Not one of the MGs but the Toyota failed to start yesterday morning. Weather was the unique British combination of just short of freezing and everything soaked in dampness. Cranked over normally, fired once, then cranked with a really strange noise but wouldn't fire again. Spark OK, fuel OK, cambelt OK, compression way down on one cylinder which was odd as it had been running fine. Battery cranking voltage was 8 point something which is lower than it should be but jumping it from the V8 (which started as normal) made no difference. As I had been cranking it a bit I put it on charge while I pondered things. Then tried again about half an hour later and it cranked faster and was obviously trying to fire. After about 30 secs of that it eventually staggered into life, obviously firing on 3 cylinders and sounding like one of the exhaust valves was sticking open. After a few moments of that it started running normally, presumably as the sticking valve unstuck. Between us my son and I have had this car over 10 years with nothing like it before, the only other difference being I had changed from using Shell ordinary unleaded to Tesco petrol just two tankfuls ago. I've heard other comments about supermarket petrol in the past, has anyone experienced anything like this?
Paul Hunt 2

Paul,

As you are in Solihull I guess the Tesco in question is the one on the A34 near the M42 junction. I work just across from there on Blythe Valley Park.

Recently they had a problem at that Tesco with, I think, diesel in the petrol! Perhaps this is a factor.

David
David Witham

Paul,

In the 80s I met an MG enthusiast with an MGB and a TF that he had built up from parts using a converted Y type chassis (basically this meant he could afford a TF!). He had some distinct views on Petrol and reckoned that Shell was the best, followed by the other big brand names, followed by Supermarkets and the lesser well known brands. He supported this with loads of correspondence with the companies and had researched it amazingly well.

After this Shell started marketing different kinds of 4 star leaded that supposedly cleaned out the engine and I think he changed his view.

What does all this mean in the 21st Century? I haven't gor a clue.

My petrol problem is that the MGB can be a right pig to start when hot, presumably due to unleaded varourising when the car stands. It started doing this towards the end of the 4 star leaded era when it was becoming more and more like unleaded.

Does anyone out there have this problem and perhaps a solution?
John Prewer

Paul
I think you'll find Tesco gets it's petrol from the same source as most other suppliers, there aren't a lot of refineries in the UK. Years ago I worked near the Grangemouth plant and watching all the different tankers coming out made me rather cynical of the advertisers claim that one petrol was better than another.
Ron
R. Algie

Same story here in the US. There's a large storage facility near my house and I see trucks of all brands coming out of there.
My uncle works for a facility up in Tennessee and he says that while some companies do add various chemicals afterwards (e.g. Techron), it's mostly down to the condition of the holding tanks at the local retail location. Some maintain their equipment better than others.
Those that move fuel quickly (usually) have less water/sediment build up.

Dave
David Steverson

Paul

Ethanol has a higher heat of vaporisation than petrol and can make cold starting an engine a problem. It can seperate if stored and has an affinity to water.
Most UK fuels use approx 5% ethanol and only the additives vary. Optimax uses Toluene not sure about BP Ultimate and the new Tescos 5% bio-ethanol.

Paul
Paul

Hi all.

The 'tankers all come from the same depot' question keeps cropping up, I don't have the answer, but I would like to !.

Firstly, the tankers leave the depot (in the uk) with unleaded, diesel, 'special' unleaded, 'special' diesel, etc.. just because it comes from the same depot doesn't mean it is the same fuel.

Even if the fuel comes from the same depot delivery hose it might be different fuel, uk forecourt fuel pumps used to dispense 2*, 3*, 4* and 5* from the same hose on the same pump.

Secondly, does anyone know how additives are put into the fuel ?.. are those cylinders at the rear of tankers full of additive, are additives added at the fuel depot, are they added at the refinery... ?.

Moving on, I can't see why a change of fuel would cause a valve to stick, though I guess it just might cause a piece of debris to stick in the valve seat and so prevent a valve from closing. I would have expected a stuck open valve to make the engine crank more rapidly, not less. I would guess that cranking an engine with an inlet valve not closing might cause the engine to make strange noises.

Don
Don

I can tell you the situation in Memphis, and I assume it's the same most everywhere. One of our car club members in an engineer at the local refinery depot, so he knows the facts.

In this area, every drop of fuel comes from the same tank regardless of brand - with one exception. That exception is Amoco Ultimate, the clear gas. Everything else is loaded at the same source, and the proprietary additives are injected into the pipe as the fuel is transfered to the truck - and those additives are measured in something like parts per million.

I you get a tank of "bad gas" is is almost certainly an issue with that particular retailer's tank.
Joe Reed

Joe describes the UK practice well - the principal difference is the additives (which are expensive). Initially our supermarkets economised on the additives but were shamed into matching the oil companies - by public opinion.

The problem here as all concerned are aware; it is not possible to prove that a single tank missed out on the additives without great expense.

Paul - the most impresive things about the Japanese cars - is the quality of their engineering - built to last a certain number of hours and engineered to fail thereafter - in Japanese hands the MGB would have been one of the most reliable cars on the road - there would have been a handful (of trailor queens) remaining.

Roger

If the problem returns - add your own......
RMW

http://www.honestjohn.co.uk/faq/faq.htm?id=46 and http://www.greenergy.com/products/99_octane.html seem to contradict the oft expressed view that all petrol is the same.

"built to last a certain number of hours and engineered to fail thereafter" Some years ago I was connected with the purchase of switches from a Japanese company and we wanted to know what life we could expect. They refused to say and asked us what life we wanted. We did, and they supplied some examples for testing, which did exactly what Roger has said above. However I've never heard that applied to Japanese cars. But then again, you look on the web for information on Honda main relay and there are thousands of reports of failures, so not all the stories are true.
Paul Hunt 2

Thirty years ago, I would say that Supermarket fuel differed greatly from branded fuel, and branded fuels varied from station to station. As exhaust emissions became more tightly controlled, the Guv'ment became involved in the composition of fuel, and this runs so deep I'm suggesting, like others, that the ONLY difference is additive packages. When I lived out in California there were summer grades, winter grades, those with oxygen content (usually the highly carcinegenic(sp) MTBE- hows that for cleaning the envirornment). Is a refinery set up for California fuels going to change setup to support Nevada fuels, and then Airzona fuels? Likely not. One refinery will support the blend for one region, another for another region. Bottm line is the state controls general content of the fuel.

Which leave the local distribution facility. Contaminants may be introduced here, which is why I try to used high volume distribution centers- supermarkets, stations adjacent to a freeway offramp. If there's a line, that's the place I head, since contaminant concentration will tend to be lower if there are more fuel changes per given period of time
greg fast

5th gear test on optimax, bp ultimate and supermarket fuel on three cars:- a 81bhp clio, a 172bhp golf gti and a subaru impreza with 235bhp. They connected each up to a power/tourqe machine a did six runs for power increase only, each time resetting the ecu.

Clio- supermarket 81
BPU 81
Optimax 81

Golf-supermarket 172
BPU 174
Optimax 177

Impreza-supermarket 235
BPU 247
Optimax 249
Paul

The quetsion of additives is an interseting one. Whatever additives are deemed necessary are put in at the refinery by the fuel seller (Shell , BP or whomever). Storage is normally a function of safety , conveniemce , access to major highways , rail limes etc and it is common for many refiners to share a storage facility. This is also a function of municipal zoning since one large facility makes more sense than several smaller ones. The transport is simply that and it is common for a truck to carry another brand different from the one labelled on the side.

As an aside the supermarket fuel here in Australia is supplied by the main brands (BP , Caltex etc) regardless of what it says on the advertising outside!

The problem experienced sounds more likely I think due to poor storage and handling than any deficiency in the product.

Cheers , Pete.
Peter Thomas

Hi all.

Thanks for the figures, Paul, they make interesting reading, do you happen to know the nominal CR's of the three engines ?.

My guess would be that the higher power outputs would coincide with higher CR's.

Don
Don

This thread was discussed between 09/01/2006 and 13/01/2006

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