Hi,

Which unleaded should i use with a 5.0sc? normal unleaded or super unleaded?

Thanks

Aziz MY15 5.0SC

Super ,
You can run on regular but it will burn hotter and ignite sooner so the knock sensors will have to retard the ignition to compensate , High octane doesn't have more power per se but it lets you engine run at it's most efficient . 2008 MY Supercharged
Rimini Red / Jet
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I don't want to ignite the debate about using expensive fuels laced with magic additives but I have always used the local Tesco for forty or more years , buying their cheapest fuel for diesel and petrol and never had a problem. I think I read somewhere they are the largest fuel retailer in the UK and since I got my latest car I must be one of their best customers. I only speak from my own experience and as I don't understand Axles comments about knock sensors etc he may well be right. Geoff

I have had 8 supercharged and always run on Super unleaded and thats waht jlr tech suggest

There's a difference between octane & additives - even supermarkets will generally sell 95 and 98 (super) unleaded.

Some companies will then put further additives in an call it 'ultimate' or similar.

Axle is referring to octane - and a higher octane will help a modern high performance engine run better - and it would seem odd to buy a SC and not want the maximum performance from the car - so 98 all the way

Additives - as Geoff points out - is a different debate..... I think there must be a case for them otherwise it would have been a widely reported scandal by now - but I accept there seem to be sound arguments either way.

Actually to me it would seem odd to buy a car (any car) then ignore the manufacturers handbook which in my case says 95 RON, which is standard Unleaded, so its probably OK, its certainly been OK for me so far. Geoff

95 ron might be standard in the UK but around the rest of the world it is super but regardless of that with any forced induction engine you should put in the highest octane you can get your hands on to get the best out of the engine .
91 ron is standard here and I think the good ol USofA can go lower but don't quote me on that one . 2008 MY Supercharged
Rimini Red / Jet
four zone climate
remote park heater
and no ugly kid windows.
magnus satis quod turpis satis

There is no benefit (both in terms of performance or fuel efficiency) in using a higher octane fuel than the minimum required by the manufacturer.

However, if you use a fuel with a lower octane rating than that for which the engine is designed, then the anti-knock function will reduce performance and efficiency.

If the manufacturer requires at least 95 octane petrol, then buy that. No point buying 98 (or higher) octane.

I might be talking rubbish but I believe the debate on 98RON and 95RON is dependant on the car's ability to adjust its ignition settings to get the best out of 98 octane petrol.

If your car is over about 10 years old, the ECU cannot recognise which fuel it is using so it will have been set up for 95 or 98. Use what it says in the manual. If it is more recent, then it probably can adjust the ignition/fueling. You then will get more performance per unit of fuel (so more economical at low revs, more power at full revs).

Or something.

You might be right …


















.… about talking rubbish.

https://en.m.wikipedia.org/wiki/Octane_rating

I notice a difference between normal and super diesel in my SDV8, its quieter and a tiny bit keener, nothing in terms of economy though.

You are comparing apples and pears; petrol and diesel, octane and cetane ratings, spark ignition vs compression ignition. The OP was about petrol octane rating.

Copied this from US website:

'These automakers have raised the bar. TOP TIER Detergent Gasoline help drivers avoid lower quality gasoline which can leave deposits on critical engine parts, which reduces engine performance. That’s something both drivers and automakers want to avoid.'

I have both petrol and diesel RR's and have used supermarket fuels on both including Esso high octane petrol.

Notice no massive difference. However, since changing to Shell V Power in both I believe (especially with petrol) that the injectors remain cleaner and exhaust sensors happier.

It's correct and important that the manufacturers octane rating is followed and I have seen no gain in going to any higher level, either in performance or mpg. However, I do believe that cleaning additives in the fuel in the correct ratio does maintain the engine output during its lifespan/service interval and in turn improve the efficiency and longevity of components as stated above.

So focus on cleaning fuels rather than octane (or cetane) if you desire improvement.