Petrol RON - Sparky
I have just bought a 172 and its states that it should run on 98RON petrol only, does this mean I can't use 95RON standard unleaded? The only 98RON petrol is Optimax as far as I know so must I run the car using that or is standard 97RON Super Unleaded acceptable..
Also what are the implications of running it with 95RON, if the manual states 98RON only could I conceivably damamge the engine using lower octane petrol or am I just going to experience dimished performance and maybe a bit of pinking?
Petrol RON - 547HEW
If its a Cessna 172 you need 100LL Avgas which is 102 MON min. (apprx 112 RON).

Seriously though, and without knowing what a 172 is, I would think you could get away with Super Unleaded (97 RON) for everyday driving conditions.
Petrol RON - DavidHM
It's a Clio, folks!

You could conceivably damage the valve seats (I think) but you will definitely be faced with pinking and lost performance, which kind of defeats the object of buying a 2.0 Clio over a 1.4 16v... Obviously it'd be better to put a couple of gallons of 95RON in than run out of petrol or call out a recovery service but long term, I can't see why you'd pay an extra £3k or so for the car and then spoil it to save 2p or so a litre.

This is going to turn into another 'Optimax v placebo' discussion but personally I'd be inclined to use Optimax - although the Shell stations near me are as cheap anywhere. If it were more expensive, I might change my mind. If you don't have a Shell station nearby, or it's significantly more, I can see why you'd use ordinary 97RON and it's unlikely to do any harm at all.
Petrol RON - Sparky
Yes its a clio 172 I don't have a pilot's license or the cash for a cessna,
I will use optimax as first choice if available then and generic lower octane super unleaded otherwise if there is the possibility of damage. My girlfriend is the main driver of the car anyway so loss of performance doesnt concern me (i'd be amazed if a lower octane petrol would reduce the performance to that of a 1.4/1.6 clio) but potential damage to the engine/components does. It would just have been easier to tell lher to use unleaded rather than having to explain what optimax/super unleaded is..

Thanks for your comments
Petrol RON - Pete F
If the hanbook states 'use only 98RON' then I would assume no knock sensor is fitted and there will be detonation on 95RON. You will have to check this with the dealer or look for a knock sensor on the block.

If there is no knock sensor and you run for more than a few seconds/minutes at full throttle with 95RON then the risk is engine damage. This risk would be slight or zero if 97RON is used.

If there is a knock sensor, then using 95RON will result in some power/torque reduction and fuel consumption increase depending on ambient conditions. Engine will not be damaged.

I would find it surprising for a major manufacturer to market a car that was unprotected against engine damage due to the use of 95RON. It is a Renault though!
Petrol RON - eMBe {P}
Pete F :
E39 BMW 525 manual says use super unleaded, even though the car has a knock sensor. BMW say you can use 95RON if super is not available. Although BMW have in the past paid for repairing nikasil-engines due to damage from use of non-recommended petrol, I would rather do as they say than risk using 95RON.

Super unleaded petrol that I can readily find is from Texaco and Shell stations. Other companies tend not to have all grades at all garages. And yes, using Optimax rather than Texaco Super does make a difference to my car.
Petrol RON - Pete F
I don't quite understand your point because you say that BMW say you can use 95RON. This is what I would expect for an engine calibrated to run on 98RON but fitted with a knock sensor. You will get poorer performance and economy though, so there is no point in using 95RON if 98/97 is available.

Bore damage is not influenced by the knock rating of the fuel. Could be a good excuse for not paying though.

Petrol RON - roscopervis
Where I live the Esso Super and Texaco super are 98 RON. Only Sainsbury's are 97 which, I believe, wouldn't make much difference.

Optimax is 98.4 RON I believe.
Petrol RON - ShereKhan
I would have thought that the ECU's for cars sold in this country would have been adjusted to accept for the petrol sold in the UK market. Or doesn't the "delivery charge" and the extra cost of a car buying the car in the UK as opposed to EU mainland cover things like that?
306 2.0 SE Cabriolet
Petrol RON - Andrew Mullin
So do you guys think I would be better off using 98RON in my MINI Cooper S? Just checked in the manual and it says that the car was designed to run on 98RON, but that 95RON can also be used. When I took delivery a month ago, I asked the question and was told to just use “Normal Unleaded”. Any thoughts?

Petrol RON - GGH
I agree, bore damage is not influenced by the knock rating of the fuel, however an engine allowed to knock at high rpm (which is very hard to diagnose) will damage many things including the bore.

I seem to remember an old article by David Vizard the motoring journalist and respected engine test bed engineer. When he tested many branded American leaded and unleaded petrols for performance on a small block Chevy V8, high rpm deternation caused excessive bore wear.

I had a cylinder head and 2 pistons melt on a 1955 300SL Gullwing (fitted with a Godfrey roots blower) when BP delivered BP Super 97 instead of BP Super Plus 101 to the company storage tank.

Even on a modern car with anti knock controls, never use a petrol with a RON below the makers recommendation.
Petrol RON - eMBe {P}
PeteF - I know the nikasil bore damage issue and I was not suggesting that 95RON caused that. All I was saying was that in that case the damage occured because some drivers filled up with the wrong fuel for nikasil lined engines. So to be safe, I prefer to use the preferred fuel for the E39 as defined/designed by the manufacturer for the E39, even though they say you may use 95RON.

Andrew Mullin: Your choice whether you feel that paying 4p a litre extra is something you want to or can afford to do. Try a full tankful of Shell Optimax or Texaco Super, and see whether you notice any difference - even if it is just a placebo effect.
Petrol RON - matt35 {P}

'Although BMW have in the past paid for repairing nikasil-engines'

Never thought that BMW produced engines in the North East!

Petrol RON - eMBe {P}
Never thought that BMW produced engines in the North East!

I presume you are a Geordie and that is how Newcastle is pronounced. I wouldn't know because I lived a few years in the town near there where they hung the French Spy, if you know what I mean?
Petrol RON - matt35 {P}

Not a Geordie, but even a Glaswegian could confuse some of the Frogs for monkeys these days.



Value my car