Unleaded or super unleaded?

[GenialZ]

After seeing a fellow Aston motorist filling a Vanquish with regular unleaded I wondered how diligent or particular we all are with our petrol brands and with our RON.

From my manual: 98 RON Super Unleaded fuel recommended for best performance, 95 RON minimum.

Some super unleaded is just 97. I think only Shell and Tesco do 99. For the purpose of this poll super is anything 97 and above.

Astons only please.

[JS1500]

In the past I only ever used Shell V-Power but have recently filled up with Tesco 99 a couple of times as it's much easier to get to from my workplace.

[Jon39]

I understand that clever electronics somehow detect which octane fuel Is being used, and then adjust the engine accordingly.

The big question; can anyone tell when the throttle is pressed, which octane fuel is being used?

Edited by Jon39 on Tuesday 22 September 21:51

[kbooker]

I'm new to Aston ownership (2 days so far with my V8V) but I could certainly tell when on the rare occasion I was forced to fill up my 430 Scud' with 95 RON. When I have the choice I always choose Shell VPower

[JonV8V]

Someone will no doubt clarify but I thought older v8 and v12s didn't adapt to make the most of higher octane fuels making it pointless using them.

[RobDown]

JonV8V said:

Someone will no doubt clarify but I thought older v8 and v12s didn't adapt to make the most of higher octane fuels making it pointless using them.

I thought that too, must have read it on here or the AMOC forum. Not sure about the more modern engines though

[bogie]

Vantage V8 has a knock sensor, however the difference between 95 and 99 is just a few bhp at best, not noticeable by the seat of the pants dyno in a 1.6 ton car.

[hashluck]

JonV8V said:

Someone will no doubt clarify but I thought older v8 and v12s didn't adapt to make the most of higher octane fuels making it pointless using them.

As I understand it V12s do not but certainly the current V8s do

[gibbon]

How about does anyone notice any mpg difference? I know its hardly the most watched criteria, but i swear i get slightly more miles to a tank with the good go juice, i may however just be believing what i wish to.

[IanV12VR]

The 4.3l and 4.7l V8V engines have anti knock sensors and the higher octane rating is recommended. When I bought my DB9V I continued to use the higher octane fuel, not all the time but at least every third tankful, but was told I was wasting money as it had no effect on the V12.

However, the latest V12 engine in the Vanquish and the V12VS do have anti knock as well and have higher octane fuel recommended.

Have I ever noticed a difference - no, but I probably don't drive the car quick enough to notice

Is the mpg better - never noticed but it would have to be quite significant to offset increased costs.

I usually now use the higher octane every four tankfuls or so.

[BigMig]

I tend to steer clear of supermarket stuff as friends in the petroleum industry say that the additive packs put into fuels to the refinery, are what mark out the difference between big brands and supermarkets, which may have an effect on the longevity of the engine.

The only issue I've had with regular unleaded is that it is more likely to trip the emission service warning light on the dash. Something to do with the O2 sensor during the warm up cycle.

The annoyance with super unleaded is that the prices is never advertised on the hoardings, so you only know what premium you're paying once you lift the pump.

[Jon39]

IanV12VR said:

Is the mpg better - never noticed but it would have to be quite significant to offset increased costs.

I looked at the Shell website expecting to see a craftily worded claim, that their higher octane petrol achieves better mpg. Nothing at all. Their sales pitch is that there are ingredients which will clean your engine (only the inside) faster than 95 octane Shell.

Is it true, that an engine requires a certain minimum octane to avoid pre-ignition, but that anything higher is unnecessary?

Edited by Jon39 on Wednesday 23 September 11:03

[gibbon]

Jon39 said:

I looked at the Shell website expecting to see a craftily worded claim, that their higher octane petrol achieves better mpg. Nothing at all. Their sales pitch is that there are ingredients which will clean your engine (only the inside) faster than 95 octane Shell.

Is it true, that an engine requires a certain minimum octane to avoid pre-ignition, but that anything higher is unnecessary?


Yes, unless the timing can be adjusted, and even then, its diminishing returns.

Edited by Jon39 on Wednesday 23 September 11:03

[V8Andrew]

I always use tesco momentum

[300bhp/ton]

JonV8V said:

Someone will no doubt clarify but I thought older v8 and v12s didn't adapt to make the most of higher octane fuels making it pointless using them.

I have no idea about these cars specifically, but the use of knock sensor to detect pre-det and retard the ignition, isn't a new thing.

This means a car can be setup to run on higher octane fuel, but also run safely on lower octane fuel, but you'll find it might not run as smoothly on 95 RON and with maybe a bit less power and less willingness to get up and go. Depending on the state of the tune and how aggressive it may be.

In hot climates, or hot summer weather, you might notice this difference more so. As pre-det will be more likely in higher temp conditions.

[Ken Figenus]

If you don't have knock sensors (generally sub 500 bhp versions of V12's i think) then there is no performance gain to be had from anything above 95RON as it wont know its got this fuel! Its pre set for 95RON only.

Whether putting higher RON in there gives you a higher safety margin away from pre detonation (pinking) would seem logical. But if you are pinking with 95RON then you have greater problems!

Additives are another can of snake oil worms!

[dig123]

Always put shell V power nitro plus in as it is the first garage I drive by from where I store the car, was thinking of putting tesco fuel in but just put this in the usual run around in particular since there was a problem with fuel contamination at a tesco in Bournemouth. Try googling fuel contamination tesco then fuel contamination shell, make you wonder.

http://www.bournemouthecho.co.uk/news/11486602.UPD...Motorists_face_huge_repair_bills_after_filling_up_with__contaminateddiesel_at_Tesco_Branksome/

[Jon39]

Coincidence.
Directly opposite AM Sevenoaks, is a Tesco filling station.
There was also a fuel contamination incident there, a couple of years ago. Chaos.

[Little Donkey]

If you want the most accurate and up to date information on this sort of thing, your local friendly VW dealer are the guys to ask.

[Jon39]

Little Donkey said:

If you want the most accurate and up to date information on this sort of thing, your local friendly VW dealer are the guys to ask.

I am expecting repeated, unsolicited phone calls, with the offer of VW compensation.