The Lotus Grand Tourers

Out of curiosity, what fuel are people using in their Excels.

Unleaded (95 RON) with standard ignition timing
Unleaded with retarded ignition timing.
Unleaded with additives.
LRP
Super unleaded (with or without additives).
Anything else?
Do you have an SE or standard?

If you have retarded the ignition, by how much and have you noticed a reduction in performance?

My car is a 1990SE, 132k miles, standard ignition timing.

I normally use Tesco 99 RON, Shell Optimax or Esso Super 97.

It doesn't like the 95 stuff as much on standard timing although when I was driving 700 miles a week, I fed it standard 95 a lot since most was at motorway cruising speeds. I'm not sure but I think it was running 8/9 deg at idle instead of 10 in those days.

The Excel seems less fussy on fuel than my TVR Griffith 500 was ... I used either super, or 95 with an octane booster. The octane booster successfully cured the pinking on regular 95.

Mine's a 1986 SE. My car doesn't like standard unleaded. For peace of mind I have always tried to use Shell Optimax whenever possible. Standard timing and no problems to date. I have used other super unleaded fuels with, touch wood, no problem but I don't fill the tank with them. I have found that the fuel from any one company can differ depending on which garage you fill up in. The only thing you can rely on is the "rip off" price!

Optimax when I'm feeling rich (not very often)
The rest of the time I use standard 95Ron + Castrol Valvemaster Plus (for the octane boost) so I know I'm not mixing chemicals too much.

Premium unleaded of whatever brand, pings a bit when cold (due to the 30 degree advance setup) but seems fine when warmed up.

there was an interesting article in evo recently were they tested the different fuels available on a golf gti and the power differances from using high grade fuel were noticible, bp ultimate produced the most power, optimax had the smoothest delivery and was the drivers choice, the lower grade fuels (95ron) were not as responsive and produced less power, 10 or 15 bhp less than bp ultimate.
In the excel i'd say your unlikely to see more power, you'l just recover the power you were loosing as the car was developed at a time when 4 star 98/99 ron was the standard pump fuel, this was what it was setup to run on and this is the fuel it performs best with, the current crop of optimaxes and ulimates simply give unleaded the same kick the old 4 star had, as standard unleaded was a big drop in quality over the old 4 star.
Personally i'd say use it the handbook recomends 98 and lotus have no comercial interest in telling you what fuel to put in, also shell/bp have more additives/detergents to keep the engine inside's cleaner & the differance in cost between filling a empty tank is like 6 or 7 quid you get a slightly better millage on the optimaxes/ultimates so the real cost is only marginally more.
an one last little thing is you can also get sub standard fuel batches were its been sitting around in the tank to long an hence has gone off (lower octane rating) a gone off optimax is likely to be around the 95/96 mark an gone of 95 is lilkey to be around the 92/93 mark a duff batch of 95 would pretty lilkey lead to a tiny bit of pinking on standard igntion timing which although set up conservativley/with margin for error was setup using 98/99 petrol as the baseline, while that factory set safety net will allow 95 if it gets much lower (i'e bad batch) your pushing on safety margins lotus built in when they set the timing

Nothing to add to the excellent posts so far apart from avoid LRP like the plague.

One thing that has been agreed on is dont mix additives, and as most petrol companies never came clean on whether their LRP additive was magnesuin, calcium, sodium based etc you could be putting a real mix into your engine if you vary petrol suppliers.

I would suggest if you use 95 RON & feel no reduction in performance then use it as its cheaper. Personally I wouldn't dream of putting Supermarket petrol in my pride & joy.

I wonder if we can find out who supplies the Supermarkets?

Nothing to add to the excellent posts so far apart from avoid LRP like the plague.

One thing that has been agreed on is dont mix additives, and as most petrol companies never came clean on whether their LRP additive was magnesuin, calcium, sodium based etc you could be putting a real mix into your engine if you vary petrol suppliers.

I would suggest if you use 95 RON & feel no reduction in performance then use it as its cheaper. Personally I wouldn't dream of putting Supermarket petrol in my pride & joy.

I wonder if we can find out who supplies the Supermarkets?

They all draw fuel from the same tanks. Hemel supplied 6 major companies and others drew fuel as and when from Hemel. There is no guarentee you get the same each time unless you really stick to the same garage from a main supplier as they would normally take deliveries from the same depot. But just at the moment fuel in North London could be comeing from anywhere!!!

Optimax as a norm...

Ultimate if I need to fill up and a BP station arrives before a Shell one.

Optimax was the norm, ran smoother and no pinking.