903cc 850 Spider and 900t Amigo camper van. Both currently using unleaded only, no additive, is super unleaded better for the engine or harmful?

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Definitely not harmful. You get a higher octane rating, so may help a little with performance, or might stop some pinking (though retarding the ignition is the best bet in that case).

I haven't found any noticeable difference in the 127's or 903cc Panda's so it may be a waste of money. Give it a go and see if it's worth another 6ppl.

Membership Number: 5260

1 tankfull in 3 had startling effect on my old Punto ELX75 - would rev like never before, much smoother, more pull at all engine speeds, better economy. I think that was unusually gd result.

A study a few yrs ago showed that Tesco Super Duper was by far the best. Tho Tesco no doubt buys it's 'ordinary' from wherever, it prob has (or had then) a single source for Super.

fifth gear,motoring show on discovery channel, did a comparision with unleaded vs super unleaded.
on a vw (i think, was busy writing down the details)
BP unleaded 138.9 per litre 236.1 bhp
BP Ulimate 148.9 per litre 236.7 bhp
SHELL V Power 144.9 per litre 240.9 bhp
ESSO Supreme 144.0 per litre 240.5 bhp
ASDA Unleaded 135.9 per litre 235.8 bhp

the standard bhp was 236 bhp,
using shell v power gained a improvement .

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Hi All

I tend to use the higher octane fuels on longer trips, general the 850's tend to work better in the midrange on 98ish octane which helps the economy, I found I went further once I started to use it.
I drove most of the way from Belgium to Lemans in one day on 98ron at about 4000 to 4500 revs, it felt much smoother on this journey than the high Wycombe to dover leg on 95ron, unless it was just the roads, 680miles in one day in a fiat 850 spyder.

I did try some lead additive and 2 point octane boost with shell 98octane, that was interesting!

Tim

ps make sure you are correct with your calculations for additive quantities

Membership Number: 5222

Think I will give the super unleaded a go in the spider, it's not like it's a big fuel tank and gets used a lot so if it runs better that is all I am looking for with that.
Will probably swap to standard on the everyday car to see how it affects economy, the extra boost is immaterial if you are looking at cost and have a light right foot anyway. Currently get about 30mpg with Super on the commute but it is a lot of stop start. Can't remember what we got out of the spider last year so I won't be able to compare that. (I think it was around 40+mpg)

Will be using the Shell as they are the garages near to us, so will see how it goes.

Thanks all for you information/experiences.

Membership Number: 12302