Best petrol

As a recent newbie to a MG TF I noticed that the orange coloured engine light on the dash was showing. I returned to the garage where I purchased her from and he used a piece of diagnostic kit that came up with the problem as a "misfire on cylinder 1". He suggested that I use Shell petrol instead of Tesco/Asda. He said that their petrol was "crap". I would notice an instant improvement in economy as well as performance. Anyone else heard a similar tale, or is it an old wives tale.

Old wives tale. Petrol is petrol. There are some who suggest that the way they store it is maybe something to bear in mind, but unless its a very quiet out of town garage, most have enough turnover to prevent any problems, as long as they clean the tanks occasionally.

Of course an advantage with shell is that they have extra additives etc compared to supermarkets.

The thinkig that worries me is that there are lots of things that can cause a misfire, and telling you its just petrol suggests he is as much use as a mechanic as Gary Glitter would be as a babysitter.


You need to try and find out why its misfiring.

An occasional misfire wouldn't put the engine light on. It would just be logged as a fault in the ecu. Only a persistent misfire would put the engine light on.

Did the car seem to be missing when you were diving it?

You didn't say if you took his advice. If so did the Shell petrol give a better result?
I know here in Canada different oil companies have different additive packages in their petrol. These vary between brands, and particularly between seasons. Different additives are used in the winter to give different burning characteristics for the fuel to dael with colder temps. (Particularly important in Canada I must say!) Even though your budget petrol supplier may get their petrol from Shell or one of the other majors their additive packages will usually be different. I know here there are brands that give better results than others. It is a bit far to come for a fillup though!
Another thought...If the car was sitting for a few months the petrol in the tank may have degraded which could cause poor running. I would fill with the good stuff and toss in a bottle of whatever injector cleaner MGR approves.

Of course it could always be something like a bad injector, spark plug or plug lead as well.
If fresh fuel and injector cleaner doesn't do the trick you should take it to a garage that specializes in MGs,
or if he is in your area give Saint Russell a call.

It sounds a bit of a fob off if you ask me.

All fuels have to meet minimum standards so should be OK.

Modern fuels, however, only have a shelf life of about 2 weeks due to the ever increasing presence of ethanol which is very hygroscopic.

The car had over-wintered on his forecourt so obviously hadn't been used on a regular basis. I've been running it for about 6 weeks now, mostly little country lanes with the top down in this weather, so it hasn't had a good run. I've still got 1/2 tank of Tesco petrol left before I fill it up with Shell. So, I'll wait and see. He isn't a mechanic, but he did say that if it happened again to bring it in for further investigation. Watch this space.

McCalmont wrote: The car had over-wintered on his forecourt so obviously hadn't been used on a regular basis. I've been running it for about 6 weeks now, mostly little country lanes with the top down in this weather, so it hasn't had a good run. I've still got 1/2 tank of Tesco petrol left before I fill it up with Shell. So, I'll wait and see. He isn't a mechanic, but he did say that if it happened again to bring it in for further investigation. Watch this space.

For information, you can buy a cheap code reader that will tell you what fault codes are stored in the ecu and allow you to reset the engine light.
This is a stand alone unit Diagnostic Scanner CAN DTC Code Reader OBD2 EOBD U380 Completed
You can get cheaper kits that plug into a laptop or even ones that transmit the data to a smart phone!

Or you could buy a scangauge2 which not only does all the OBD2 stuff, it also works as a trip computer and gives live data such as oil and coolant temp.

Mk1 MGFs are not OBD2 compliant but as you appear to have a TF it'll work on your car.

As for fuel, adatives improve the fuel either giving better ecconomy and/or cleaning properties. IIRC tescos and asda will buy their petrol as cheaply as they can and without any expensive addatives to keep the price down.

I wasn't aware that there was any ethonol in UK fuel, shouldn't this be advertised as it will effect seals etc in older cars.

talkingcars wrote: I wasn't aware that there was any ethonol in UK fuel, shouldn't this be advertised as it will effect seals etc in older cars.

Since 2005, and you don't necessarily know what is what.

http://www.reuk.co.uk/Introduction-to-Ethanol.htm

I ran her dry and filled up with Shell. Took her for a run over the tops from Chester to Lincoln. Included motorway, 50 min traffic at Tintwistle and the motorway. A weekend of country lane driving and a not very sientific reckoning of about 36.5 MPG. She ran as smooth as silk - no problems. I'm filling her up with Tesco fuel tomorrow and try and see if there is a difference. Will report back.

broon wrote: Old wives tale. Petrol is petrol. There are some who suggest that the way they store it is maybe something to bear in mind, but unless its a very quiet out of town garage, most have enough turnover to prevent any problems, as long as they clean the tanks occasionally.

Of course an advantage with shell is that they have extra additives etc compared to supermarkets.

The thinkig that worries me is that there are lots of things that can cause a misfire, and telling you its just petrol suggests he is as much use as a mechanic as Gary Glitter would be as a babysitter.


You need to try and find out why its misfiring.

totally disagree...
my Excel will only run on V-Power, it is used to the higher octane and it miss-fires and will not idle at all on anything bellow 98 octane...
if i fill it up with 95, i have to add an octane booster...

perfectly plausable that the shitty supermarket fuel is the cause...

Tesco 99 is actually just re-branded shell V-Power i believe...

i never use 95 petrol in anything but the familly waft mobile...

97 or 99. I find that BP Ultimate = more miles per gallon (330miles in a tank rather than 310), and Shell V-Power was proven on my lotus to give more power on a dyno run... (about 7%, but the carbs on that are set up for the higher octane)

Yeah, if the car is setup for a higher octane then it will obviously do better on that grade.
My Nissan is optimised for 98 octane but will still run happily on 95. I've never tested fuel consumption on either though.:lol:

The MGF does appear to give more miles per tank on BP/Esso/Shell rather than Tesco/Morrison's petrol.