That's correct. The difference in rating systems leads to all sorts of trans-Atlantic confusion. Our system was the same as yours up until the mid '70s when we switched to AKI as the standard reference. Many people back then (and now) still believe that the change was an actual decrease in the octane level of the fuel rather than a simple change in rating system.

Let's not bring up the metric system.........

 

Folks, I didn't expect to stir the pot so much, but thanks, it's been good reading! I think my XJ-8 actually got less milage on the mid-grade but seemed to run well? Hard to measure precisely since the driving conditions are not constant. As some said, probably not worth the savings to skimp on the price of premium. To our British friends, had 4 wonderful years in your country in the late 70's and early 80's during my USAF years. Had my 72 V-12 XKE back then, and even with a ration of American tax free gas, it sure was expensive to drive as is now - driving that car was only for pleasure!! Nothing like a British Pub!! Thanks everybody, great forum!

 

If you want to see true feather ruffling and sabre rattling, just ask 'which oil is best'- best stand back

 

Mobile 1 all the way!!

 

Just to show we can still go out in our Jaguars here in poverty-stricken England, on Sunday we went to see my daughter at her university city of Bangor in North Wales.

After a very nice lunch in a pub overlooking Telford's famous suspension bridge, we drove out into the Welsh countryside in brilliant sunshine. Passed through Caernavon, then down to Pwellhi with a blue sea in view most of the way, and the mountains in the distance. Drove home via Portmadoc, now the terminus of two narrow-gauge railways, the Ffestiniog and the Welsh Highland. They were backing in a train as we passed the station. Gauge is 2" with Beyer-Garret and Fairlie steam locos and other lovely engines used. From Portmadoc, it was up to Ffestiniog in Snowdonia, then over the pass to Bala and Wrexham finally through Nantwich and home. Traffic was very light so we made a good pace.

We don't get many days like that one, and I was able to fill the tank at Caernavon despite our fuel shortages due to a threatened strike of the delivery drivers. Some garages in Wales were posting £1.45-1.47 a litre, though.

 

Here's a twist I just rediscovered-when you press 'premium' on the pump, you're almost 96% chance of getting a hoseful of regular, say 1 gal+. This was significant when filling my 4 gal cycle tank.

Maybe you can line up behind a corvette or similar if you can to use the same hoseful of premium.

 

My personal tests on octane boosters have shown me that regular use of them will add carbon deposits to the combustion chambers. I tried them on a beautiful modified 1965BMW R69S bike I built with high compression (11.2-1), and the plugs would foul out in 1000 miles. I finally started running CAM2 110 octane racing gas in it (This would lead foul the plugs, there was no winning either way except that before it fouled, it was the fastest R69S around!)

 

Apart from the Jaguar, I have a 1977 MG Midget, so it not being suitable for lead-free petrol I am using Castrol Valvemaster Plus, which has a lead substitute in it and also an octane booster. So far I have not suffered any problems with plugs. I always try to use 97 or 98 RON octane petrol as this has nil or little ethanol in it, (at the moment !!). So I really don't need the octane booster part of the stuff. The amount one adds is very small in relation to the fuel put in the tank, a few millilitres at most.