Shell or BP do make a difference BUT the cost is higher too,about 10% .The
power of my 740turbo is much greater and as it pings on standard petrol or
gas ,I use the 98 octane to give a bit of stick as well as synthetic oil Bp
NOT shell .The range is supposed to increase by 10%as well so its an off set
on price I guess .I have heard the mechanics can tell if your using optimax
or Bp ultimate because the engine is cleaner inside same with Synthetic oil
its much cleaner inside and runs smoother .Certainly no issues with the
engine crudding up as with dino oils .Now the issue is 0-30 oil 0-40 oil or
5-50 oil which is best year round .The 0-30 seems to be a good choice for a
cool engine with less friction but is it wise ?

I have tried all the 'Super' or 97/98 octane petrols in the many miles I've
done in my V70 T5.  I found the Optimax to be one of the better types but
the fuel economy was ok (27-28mpg at 60mph-fast cruise with plenty of brisk
acceleration) mostly I think because it made the upper rev range so useable
that I gave it more welly that with other fuels!  Texaco was another good
high-octane, which gave better fuel ecomony, & seemed to increase low-end
power but give less top end than Optimax.

On the fuel cost issue, yes the Texaco/Shell garages charge the earth for
the high octane fuels.  I go to my local Sainsburys petrol station & they
sell the high-octane generally for @1p/litre more than the 95 octane - &
often they are the same price!  Performance is on par with the Optimax &
given the fact Sainsbury's don't have any oil refineries, it could well be
Optimax!

Have fun,

I've been using Shell Optimax in my '85 240GL (B230E), 272,000kms, for over
a year now, and it's excellent. Yes, it is more expensive, but the car goes
further on a tankfull, rewarding me with the huge saving of, well,
approximately 50 cents... The car is smoother, almost spritely, and
generally feels more healthy.

I had the compression ratio lowered many years ago by means of a thicker
head gasket (not two together) as the lead content of leaded fuel seemed to
gradually decrease; I then used lead-reduced fuel when it became available.
I've no idea what the comp. ratio is now. I began using Optimax when the
owners of the small independent workshop who have serviced the car for a
number of years suggested I give it a try, as they used it as well in their
similarly-engined cars. There has been no discernable difference in sounds
made by the top end of the motor, to date.

Optimax use has combined with a lower compression ratio to produce a
delightful combination of engine characteristics and a very rewarding
driving experience.

Occasionally people at the pumps have asked why I'm wasting Optimax on a
"car like that", to which I reply: "Because it likes it."