Which Petrol to use? Advice please

Strider590

rev_henry wrote: »

You most certainly do not need V-power in a car like that - waste of money. V-power petrol is only really for high powered mainly japanese sports cars.

artbaron wrote: »

I agree with the first part but the second part is wrong. A number of cars need 98RON or higher, not just high powered Japanese ones. All that matters is whether the ECU is mapped for 98+RON. If it isn't then using it will make no difference, if it is then not using it could cost you your engine.

A lot of people make the assumption that higher octane is for more power, it's as common as people saying Golf's are the most reliable car.

Truth is, it's all about the ignition timing and compression ratios. Essentially if you built a car to take advantage of 98RON, with high compression ratios and the correct ignition timing, you'll get slightly more power, but that car will not run on regular unleaded without destroying it's pistons.

If a car will take either, then it's not built for 98RON and will see approximately zero advantage.

Cars built for Japan, are built around the fact that they use high octane fuel in Japan and as such when bought over here, really all cars made specifically for the Japanese market should be run on 98RON (actually 100RON in Japan), but it's more important in high performance cars because of the way they'll be driven.

fivetide

Strider590 wrote: »

If a car will take either, then it's not built for 98RON and will see approximately zero advantage.
.

That's not strictly true.

Subaru for example say 98 is the best as the cars in Japan run on 100 RON. However, they will happily take 95.

The ECU knows what is in the tank and adjusts the ignition appropriately. You'll get less power on 95 but the car will not destroy itself at all.

I would suspect that given the computing power in most cars these days, that will be the same for most cars that will take either.

However, still no benefit in putting it in a low model Hyundai!

Strider590

fivetide wrote: »

That's not strictly true.

Subaru for example say 98 is the best as the cars in Japan run on 100 RON. However, they will happily take 95.

The ECU knows what is in the tank and adjusts the ignition appropriately. You'll get less power on 95 but the car will not destroy itself at all.

I would suspect that given the computing power in most cars these days, that will be the same for most cars that will take either.

However, still no benefit in putting it in a low model Hyundai!

Cars built only for Japan are not built to last more than a few years, when you buy an import your buying a scrapped vehicle (due to their strict emissions laws). They won't tend to waste money making a car suitable to run on 95RON if it never will.

Back in the day, when Jap import sports/super cars were becoming common, none of them could run on 95RON without damage, but since most are now available world wide, it's different.

Japanese cars built for the EU market are different.

The ECU doesn't know what's in the tank, it uses the knock sensor to detect pinking and the retards the ignition accordingly (minor detail, not just being picky).

The thing is, if you want power out of high octane fuel, you need high compression ratios.
My Westfield runs 11:1 compression ratios, you could retard the ignition all you like but it still won't run on 95RON, in fact you would have more luck fitting injectors/glowplugs and running it on diesel. Most cars don't run this sort of ratio, the Impreza STI for example runs 8.2:1.

Without going to extremes of engine building, most normal cars won't see any real benefit from 98RON, Japanese imports will simply need it to stay in one piece, IF their ECU doesn't adjust for 95RON.

DKLS

If I am paying its Sainsburys Super Unleaded, if its for work it gets Shell V power.

fivetide

Strider590 wrote: »

Cars built only for Japan are not built to last more than a few years, when you buy an import your buying a scrapped vehicle (due to their strict emissions laws). They won't tend to waste money making a car suitable to run on 95RON if it never will.

Back in the day, when Jap import sports/super cars were becoming common, none of them could run on 95RON without damage, but since most are now available world wide, it's different.

Japanese cars built for the EU market are different.

The ECU doesn't know what's in the tank, it uses the knock sensor to detect pinking and the retards the ignition accordingly (minor detail, not just being picky).

The thing is, if you want power out of high octane fuel, you need high compression ratios.
My Westfield runs 11:1 compression ratios, you could retard the ignition all you like but it still won't run on 95RON, in fact you would have more luck fitting injectors/glowplugs and running it on diesel. Most cars don't run this sort of ratio, the Impreza STI for example runs 8.2:1.

Without going to extremes of engine building, most normal cars won't see any real benefit from 98RON, Japanese imports will simply need it to stay in one piece, IF their ECU doesn't adjust for 95RON.

Absolute guff.

I happily ran an FTO MIVEC on 95 RON for years. I did 60,000 miles in the car and it never missed a beat and still pulled like a train when I sold it.

And yes it was a Jap import not a Ralliart one (which were only official imports anyway).

If you buy a Japanese import you are not buying a scrap car at all. You are buying an old car potentially but the reason they come up is because the MOT (or Sha'ken) is very expensive. There reaches a point where the cost of the test outweighs the value of the vehicle. Many are low miles and rust free so to describe them as scrap is very wide of the mark.

Strider590

fivetide wrote: »

Absolute guff.

I happily ran an FTO MIVEC on 95 RON for years. I did 60,000 miles in the car and it never missed a beat and still pulled like a train when I sold it.

And yes it was a Jap import not a Ralliart one (which were only official imports anyway).

But that's not a Jap only vehicle then is it? The engine, the wiring loom, it's been (or at least a variant has been) designed for export.

fivetide

Strider590 wrote: »

But that's not a Jap only vehicle then is it? The engine, the wiring loom, it's been (or at least a variant has been) designed for export.

Hey, it's ok to admit when you are wrong you know.

alastairq

My Skoda has some 30 thou-plus skimmed off the head....runs bike carbs, and the ignition is set via a rolling road...or.....an afternoon of pounding up and down a local road, spanner in hand?

Regardless of where I swing the ignition timing, it pinks like blazes on 95 octane fuel...runs very nicely [thank you] on 98 octane.

All down to compression ratio.

Always was the case with car when I started driving...some, with higher comp ratios , would need 4 star or 5 star..others 3 or better still, 2 star [91 octane, IIRC?}

Running a AH Sprite 1275cc, it was happy on 3 star [95 octane?]...no revving if on 2 star [pennies counted even then]....of course, all well leaded, 'twas all that could be had.

Nowadays, I'm lost, when people mention ECU's adjust to suit the fuel, etc...or..even, adjust to suit the driver's style?

Wot's that all about , then?

Joe_Horner

alastairq wrote: »

Wot's that all about , then?

It's about the Colt 3 cylinder diesel hatcback we had a few years back weighing as much as my first car (a BMW 2500 straight six - basically 7 series of the day for those who don't remember them) because of all the electronics that are needed to get today's on paper fuel consumption figures. Which bear no relation to what people actually get when they drive them like people drive cars.

In other words, "Wot that's about" is pretty much the electronic (and manufacturer supported) version of magnets-on-your-fuel-line / lumps-of-lead-in-your-tank snake oil

But, that's progress - and someone has to find a way to sell people a new car every few years

alastairq

and with that, I guess the only new car I'd ever consider buying would be a Dacia Sandero....