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MG MGB Technical - Octane ratings in Scotland?

When we visited Yorkshire and the Lake District with the MGB last year, we ran into unexpected problems finding 98 octane petrol - or indeed knowing how many octane we put in our tanks!

It turned out afterwards that filling up at Shell stations would have been sensible, as their pumps are clearly marked.

We are now going to Scotland in a few days. How is the petrol situation there?

Tore





Tore

Hello Tore, all over the UK the petrol available has to conform to a BS standard. So you shouldn't have any problems, I run my roadster on 95 octane fuel with Castrol Valvemaster plus,this help protect the valve seats and give a slight octane boost. You can get higher octane petrol such as Shell optimax.
Hope you have a good trip to Scotland and hope the weather is good.
regards johnwr
john wright

Hi Tore, the octane ratings of petrol in Scotland are exactly the same as south of the border so you will not have any problems. Have a good stay.
Iain MacKintosh

Nice to know. A problem last year was that many pumps were not clearly marked with the octane number, and "premium" turned out to be a very variable quality!

Tore
Tore

You should find plenty of Shell garages in Scotland where you can fill up on reasonably high octane but slightly expensive Shell V-Power petrol, the replacement for Optimax. I find that I dont have to bother with additives with this, and have set up timing with it.

Hope you have a fantatsic time in Scotland wherever you go. Certainly plenty scenery and B-roads to tempt you.

all the best
Mick
m rae

As above, the Shell is excellent, and should be for what it costs. Generic premium is not useable in my car, if I cant get Shell I find it runs fine on Esso Super Plus.
Stan Best

I found Shell V-Power to be fine, it's 99 octane.
I'm currently using Esso Supreme (97 octane) with Castrol Valvemaster Plus - this also seems to be OK.
Brian Shaw

This may be a dumb question, but is there any disadvantage from using bog-standard unleaded (in an unleaded conversion)? Is it worth shelling out the extra for premium brands or additives?

James
JP Mutton

I've used the bog standard unleaded in both a TR6 and an MGB for years without any problems, they both have hardened exhaust seats, but I'm not convinced even that's necessary if you don't continuously drive at motorway speeds.
Ron
R. Algie

JPM

MGBs were originally designed to run on 5 star petrol which was 100 octane. There would be a slight power loss if 95 octane was used and dieseling/running on
or pinking could be experienced.

Rob
R J Collier

I had problems finding enough super unleaded in Scotland a few years ago, and the pinking and running-on was so bad on 95 I had to retard the timing slightly, which I don't like doing as it saps power and increases running temps.

I've actually found little if any difference between 97, 98 and 99, although all are better than 95, and none as good as the old 4-star. I never had mine early enough to run it on 5-star, nor used enough genuine 4-star that *is* available now (at a reputed 99.5 or better) to see a difference.

Grade and hardened seats/'unleaded head' are completely unconnected - hardened seats won't affect pinking or running-on either way, and the grade won't affect seat recession either way. Reportedly if your engine has covered at least 40k on leaded petrol, and the valves are not replaced or the seats recut, there should be enough lead leached into the surfaces to protect them for many tens of thousands of miles. America lost lead many years before we did, and whilst some poeple did have hardened seats and different valves fitted many more didn't and I've never heard of anyone suffering valve seat recession as a result. The test for recession consisted of running an engine at maximum revs and load for many hours, and an A-series engine at that which is supposed to suffer the most. Even regular motorway use is unlikely to match up to that.
Paul Hunt 2

Just back from a happy week (except for the guy that backed into my bonnet, mentioned in another post) on the west coast of Scotland, I can confirm that finding 98 octane petrol was no easy task! When climbing Applecross I really wished I had retarded the ignition from 10 to 8 degrees or so before we went, but keeping the revs up helps, of course.

We discovered that some Gleaner petrol stations sell 98 octane petrol that is really Shell - I believe? That saved the day for us - particularly for the TR6 driver who has tuned his engine to almost 200 bhp!

Tore
Tore

This thread was discussed between 08/07/2007 and 22/07/2007

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