MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Ethanol free and UP TO 5% (UK)

Petrol, octane, additives and ethanol (as at 13/9/21)

Generally it's the higher octane options that have the (higher) additive cleaning packages.

In order of octane rating, with the two ethanol free fuels at the top of this list:


Esso Synergy Supreme+ 99
o 99 octane
o double the detergent additive to Esso regular (and friction reduce)
o Esso super unleaded petrol (Synergy Supreme+ 99) although labelled E5 is ethanol free (except in Devon, Cornwall, North Wales, North England and Scotland).


Jet Ultra
o 97 octane
o cleaning additive package
o ethanol-free only in the northern parts of Scotland and Isles of Scotland.


Tesco Momentum 99
o 99 octane
o cleaning additive package
o UP TO 5% ethanol


Shell V-Power
o 99 octane
o 3x more cleaning molecules than Shell regular
o UP TO 5% ethanol


Texaco Supreme
o 97 octane
o cleaning additive package
o UP TO 5% ethanol "to much of the country" – so not all


BP Ultimate
o 97 octane
o cleaning additives package
o UP TO 5% ethanol



Nigel Atkins

Well done, Nigel. Good bit of research.

As we know, the super unleaded will eventually go the way of leaded and we'll all then have to use ethanol, but in the meantime it's useful to know what's the best of the bunch.
Peter Allen

Thanks Peter, it wasn't really much research originally and this is just an update with some info taken from other posters.

Big debate about what's best and what's needed or not for our ancient crude technology, a lot of it as always based much on personal beliefs (as with oils, religions, Covid, climate change, etc.).

I just offer a very non-comprehensive list to show there is choice.

Personally I like the additional cleaning additive packages of the higher octane fuels but I could be fooling myself and wasting my money, I have a mild belief in them, with a very little proof to myself, which can fluctuate.
Nigel Atkins

I filled up my MGB a couple of weeks ago with the Esso 99 octane which is supposed to be ethanol free (in the midlands) prior to doing the midget Road run around the Cotswolds. I cant say my B ran any better on it than the previous E5 95 octane. I did about 110 miles so some chance for the additive package to work. We are stuck now with buying protection grade super for our classics. I'm sure my modern TF will be fine on E10
Paul Hollingworth

Depends on your car of course but I don't think 110 miles is very much chance, that's what 3 gallons or 4+ if you've got your toe down.

Lots of owners say they've been running MGBs on E10 and higher ethanol for decades without issues so you have lots of choice and not stuck at all (only perhaps stick in mud). 😁

Most of the MG Runs I've been on were more of a mild trot or often mild velocity parades where the owners don't know their cars well enough or know them well enough to only bimble them along, nothing wrong with a bimble now and again but it's not a run. 😊
Nigel Atkins

Used one tankful of Tesco 99 in the V8 after always running it on supermarket 95 and that seems to be running better, as well as lower consumption over a regular 200 mile journey which surprised me. But one tankful isn't enough.

Some say their car runs better on one particular brand of fuel, even one particular brand of spark plug. The cars were always different given the manufacturing tolerances of the day and who services them, even more so after many decades and tens if not hundreds of thousands of miles, and replacement parts.
paulh4

Has anybody any thoughts on ignition timing with these various grades and octanes? I've run my 18V engined '72 Roadster on super unleaded for a while now, and occasionally on what was 95, but never saw a real difference in performance. Just used the higher grade in deference to the 8.8:1 compression ratio.

I've just assembled another 18V replacement engine (+60 bore, std larger inlet valves, std compression) and wondered if I should just go for the factory setting initially.
Peter Allen

In my experience with the high-compression engine you can run with more advance on the higher octane. In the 70s I used to set timing for no pinking and got more advance than book which gave better performance and economy. With this roadster I couldn't get more than book, and with the change to unleaded had to retard it slightly. I've always run it on the higher octane except for one trip in Scotland where I could only get lower and had to retard further, with noticeably poorer performance and higher running temps.

The fuels now are so different to originally, plus components with many tens of thousands of miles under their belts, that the book values are no longer relevant other than as a starting point. Haynes says to advance until faint pinking is heard when accelerating at full throttle in 4th from 30 to 50. I think that's too aggressive, for one thing you can get pinking at part throttle but not full throttle, so I chose to go by just short of pinking at any combination of throttle opening, revs and load.

YMMV
paulh4

As Paul has put the fuels now are so different plus components quality (some better some worse) and with many tens of thousands of miles use make the book values a lot less relevant but good as a starting point.

I've always recommended following the relevant Driver's Handbook but it must be remembered that those were written for new factory specification cars at that time with all that was around and prevailed at that time and the cars and things have changed since then, what was good back then might be poor now, or visa-versa.

Not only are there variations in all cars but also in the people that drive them and what they experience (and often believe), what works for one may not for another or all.

Thorough road testing is the only real way to know what best suits, and I think it takes a couple of tankfuls (with perhaps any adjustment considered required) to get an idea of the fuels.
Nigel Atkins

I have been used to setting my B to factory settings then sneaking on a couple more degrees of advance with the Vernier (25D distributors only). Now I've got electronics instead of points I hope I can rely on the timing not moving. Fairly recently I thought I heard some faint pinking when running on E5 95 octane (regular) so I knocked the couple of degrees off. Didn't seem to effect the performance. Maybe now I'm running on Super E0 I'll put it back on. I don't see how I can take advantage of the higher octane if I don't. My engine has a Burgess Econotune head and the block has had a light skim and a +0.040 re-bore so will be higher compression than the standard 8.8:1. I've no way of knowing by how much. On a compression test it was pulling 170 psi so nothing too extreme.
Paul Hollingworth

Why not try putting going back to your old setting or even a little more for the Esso 'E0' and see what happens. Bear in mind the E5 are up to 5% so might vary a little between brands and even fills. I thought I read somewhere V-Power was found to be (average?) of 2-3% but this might not be accurate and have changed.

If you do the change it might mean that if you have to fill with E5 or 95 E10 after this the difference may be more noticeable, when I had my (1973/4) 1800 GT and used Shell Optimax(?) I noticed the difference more when using other petrol (and pinking) more than any improvement when first switching to Optimax(?). By this I mean I noticed or appreciated the Optimax more when it wasn't used, didn't know what I was missing until it wasn't there.

I've got a fully electronic top and bottom dissy (123-ignition) and it's timing seems solid from when it was fitted 12 years ago.

On Peter's rollers it was found that the plugs were best set at +3 thou (28) to take advantage of the stronger more consistent dissy (and lack of ancient HT cables) on my Midget.

Fuelling and (comparison not ego) figures have changed over the years possibly with wear on car but also possibly the changes of fuel available at the times.

You could ask Peter what he's found if Esso 'E0' users have been on his rollers, or with (former) E5 95.
Nigel Atkins

This thread was discussed between 13/09/2021 and 17/09/2021

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.