Diesel vs Premium Diesel

[seasink]

The engineers who spent huge sums and much time designing these PSA engines say to use 95. They designed the engines for it.

Ferrari engineers designed for 98, so use it in your Ferrari.

Do petrol companies and their marketers know more about our engines that the engineers who designed and tested them? My money is on the designers.

 

[Haakon]

Nah, they're not being illegal. There are possibly some retailers out there that are better at actually selling 98 or close to it, and if you have a custom engine that has been specifically dyne tuned for that fuel from that retailer then sure you should use that fuel.

Maybe the EVO 8 is also a special case as I recall some were factory tuned for 98 in the JDM.

But there really short version is buy the fuel the car was tuned for. Most of our frogs its 95 and you will get ZERO benefit from anything else. Remember the energy content of fuels is all the same - 95 and 98 dont have more bang in them, its just about knock resistance for the given compression and not going into a limp/safe MAP when excessive knock is detected.

As for all the other shit they put in the marketing claims, if some dubious cleaning additives are going to make any difference your engine already has bigger problems...

 

[Whippet]

Hi.

I tried to find a list of production vehicles on sale in Australia that have engines that require 98 and no less. I suspect there are very few.

Does anyone have any candidates?

Cheers.

 

[N5GTi6]

I can't find any local servos selling 'Diesel' - they all seem to have 'Premium Diesel'. I just buy what I can get. I've looked up 10 servos around me and none list 'Diesel' - all list 'Premium Diesel'. I have to admit I don't even look at what they're selling - I just use the pump labelled 'Whatever Diesel'......it's all the same, right ?

One thing I won't buy is an ethanol blend petrol. Taking food out of the food stream to make ethanol doesn't make sense.

Cheers

Justin

 

[garryw]

You guys have just ruin my night!!
I have (had) 3X406 Hdi, 1X 307 HDi, 1X 508 HDi, always used the cheapest fuel!. No issues. HOWEVER....
I have a couple of planes. In these I have always used 98 (you don't want detonation when flying!!). Even to the extent of draining out the 98 (yes 100l) and giving it away, if it has sat in the tanks for 3 months (see ownership of HDi above). Only so much you can use in the mower.
Generally various people have commented on 98 and how good it is, but I have always been conservative. Did it really matter, it's just money

 

[Peter C]

I can well understand you being fussy about plane fuel!

 

[DoubleChevron]

You guys have just ruin my night!!
I have (had) 3X406 Hdi, 1X 307 HDi, 1X 508 HDi, always used the cheapest fuel!. No issues. HOWEVER....
I have a couple of planes. In these I have always used 98 (you don't want detonation when flying!!). Even to the extent of draining out the 98 (yes 100l) and giving it away, if it has sat in the tanks for 3 months (see ownership of HDi above). Only so much you can use in the mower.
Generally various people have commented on 98 and how good it is, but I have always been conservative. Did it really matter, it's just money

I'm sure avgas will be a MUCH higher quality fuel. I bet it has lots of stabilsers and knock resistance figures as quoted. I couldn't imagine it going "off" as quickly as pump fuel from a servo (same deal with fuel purchased at the docks).

 

[Greenpeace]

I'm sure avgas will be a MUCH higher quality fuel. I bet it has lots of stabilsers and knock resistance figures as quoted. I couldn't imagine it going "off" as quickly as pump fuel from a servo (same deal with fuel purchased at the docks).

Avgas still contains lead.

 

[505604]

I haven't looked at the pumps since Ampol took over most/all of Caltex's fuel stations, so I'm not certain if it's still true.

What I used to observe was that Caltex fuel stations used to sell Diesel fuel (probably with a fancy marketing term) and Truck Diesel and that was priced usually 2 cents per litre lower than Diesel. I thought, as explained above, there was no difference in the fuel, so, at the Service Centre at Yass, NSW, near the junction of the Hume and Federal Highways, I went to the truck area to fill up. I was forced out of the area. The console operator would not activate the pump I was at!

I have observed some BP fuel stations following this same horrible practice of late. But sometimes, their "Truck Diesel" is even more than 2 cents per litre cheaper than regular Diesel. I think that 4 cents per litre is the biggest difference I've seen.

 

[PeterT]

I have a couple of planes. In these I have always used 98 (you don't want detonation when flying!!). Even to the extent of draining out the 98 (yes 100l) and giving it away, if it has sat in the tanks for 3 months (see ownership of HDi above). Only so much you can use in the mower.
Generally various people have commented on 98 and how good it is, but I have always been conservative. Did it really matter, it's just money

Why aren’t you using avgas?

 

[Dijon16]

Two observations, one for each cent´s worth.

One, re the RON, if everyone is right, then either a multi-billion dollar refinery or importer does not include an industrial chemist to actually produce or check what they claim it to be, and think that they are OR any outlet can dilute, trash the brand, and get away with it.

I find that hard to believe, Mr Smart.

I would have thought that any controlled, observed and documented procedure whereby someone, especially a monitoring body, obtained and tested the alleged 98 fuel, and found it not to be, could take them to the cleaners.

Two, many years ago, when the price difference between 91 and 95 was 6 cents, and between 95 and 98 was 4 cents, A Current Affair did a usage test around one of the tracks, probably Oran Park it was that long ago.

They lined up the different grades in the same car with all the same parameters. I think that they got Ian Luff to do it. He was the motoring world´s version of Molly Meldrum of the time.

They found that there was x% increase in economy between 91 and 95, and another whatever % to 98. So there was a measurable increase in mileage, no matter how small, but whether that equated to the % increase in the cost of the fuel, the result escapes me.

I am not saying that that is the case now. Several generations of fuel injection and computerisation have come and gone since then.

For the record, I tend to always try and get normal diesel. I will pay the extra for the premium diesel if I have to go out of my way to get to the cheaper stuff. Max 70l at 2c difference, that is worth about a 7km detour – at the most. Normally I CBF going further than across the road for the cheaper stuff.

 

[seasink]

Truck Diesel

Are your sure the truck pump was suitable for your car? These have big nozzles and a high flow rate to suit very large tanks.

You can fill a classic old Land Rover with its deep underseat tank and wide mouth, but not my C5 with small mouth and shallow underboot tank. Cars also have misfuelling devices.

Perhaps the price difference is a really discount for large purchases, like 200 or 300 litres.

 

[505604]

Are your sure the truck pump was suitable for your car? These have big nozzles and a high flow rate to suit very large tanks.

You can fill a classic old Land Rover with its deep underseat tank and wide mouth, but not my C5 with small mouth and shallow underboot tank. Cars also have misfuelling devices.

Perhaps the price difference is a really discount for large purchases, like 200 or 300 litres.

Some cars have misfuelling devices.

Have you ever looked at the filling mouth of a Peugeot 604?

If it's a discount for large purchases, they should advertise it as such. They shouldn't advertise it as a price of Diesel for sale.

 

[DoubleChevron]

I haven't looked at the pumps since Ampol took over most/all of Caltex's fuel stations, so I'm not certain if it's still true.

What I used to observe was that Caltex fuel stations used to sell Diesel fuel (probably with a fancy marketing term) and Truck Diesel and that was priced usually 2 cents per litre lower than Diesel. I thought, as explained above, there was no difference in the fuel, so, at the Service Centre at Yass, NSW, near the junction of the Hume and Federal Highways, I went to the truck area to fill up. I was forced out of the area. The console operator would not activate the pump I was at!

I have observed some BP fuel stations following this same horrible practice of late. But sometimes, their "Truck Diesel" is even more than 2 cents per litre cheaper than regular Diesel. I think that 4 cents per litre is the biggest difference I've seen.

Truck diesel will just be a high flow pump .... the same stuff will be coming out of the bowser no doubt ....

 

[Whippet]

One, re the RON, if everyone is right, then either a multi-billion dollar refinery or importer does not include an industrial chemist to actually produce or check what they claim it to be, and think that they are OR any outlet can dilute, trash the brand, and get away with it.

I find that hard to believe, Mr Smart.

I would have thought that any controlled, observed and documented procedure whereby someone, especially a monitoring body, obtained and tested the alleged 98 fuel, and found it not to be, could take them to the cleaners.

Hi - The point that was made by others and also in post #7 is that there is no Federal Governement standard for 98RON, as there is for 91 & 95; it only has to meet the standard for 95RON. So if a vendor makes a representation about 98RON then it is up to them to provide their customers with the confidence that they are getting what they purchase. Hopefully you get what is says on the pump, but who is checking it?

A Current Affair did a usage test around one of the tracks, probably Oran Park it was that long ago.

They lined up the different grades in the same car with all the same parameters. I think that they got Ian Luff to do it. He was the motoring world´s version of Molly Meldrum of the time.

They found that there was x% increase in economy between 91 and 95, and another whatever % to 98. So there was a measurable increase in mileage, no matter how small, but whether that equated to the % increase in the cost of the fuel, the result escapes me.

Hi - A Current Affair - sorry I just cannot accept this as a reasonable empirical test. According to mechanical engineer engine designers an engine that is designed to run with 91 RON, cannot obtain anymore performance or economy when running on 95 or 98, that is not how it works. They all have the same calorific energy content. There is no "magic" in the additive pack that enables a "standard performance" engine to become a high performance engine. In a much earlier post in a different thread, Greenpeace sort of proved the same thing in his Berlingo using a few tankful’s of 98 over a lower RON, no performance increase or reduced fuel consumption.

High performance engines in production vehicles are typically designed to have higher compression ratios, maybe with different valve and ignition timing profiles and also these days with turbocharging, typically 95RON is used. There might be some high performance engine designs that specify 98RON. But it is the engine design that delivers the high performance, not the energy in the fuel - which is the same. The 98RON is only used to push the onset of detonation further away than could be achieved with 91 or 95.

If the same high performance engine is supplied with petrol with lower RON than specified, then the knock sensors will feedback an earlier point of detonation onset to the ECU, and the ECU will typically retard the ignition timing slightly to prevent detonation, and thus the engine will have reduced performance, and maybe increased fuel consumption. I don’t know this as fact but the ECU might also reduce the turbo boost a little as well.

The only exception to this is if the engine in the test vehicle was a high performance engine and 91 was used, then the ECU would "detune" the engine and it would have reduced performance and maybe increased fuel consumption. Then when the engine was supplied with the 98RON fuel that it was designed for, then voila it has increased performance. Who would have guessed.

My final comment, use the RON fuel that the vehicle and engine were designed for. It is usually on a sticker under the fuel flap.

Cheers.

 

[505604]

High performance engines in production vehicles are typically designed to have higher compression ratios, maybe with different valve and ignition timing profiles and also these days with turbocharging, typically 95RON is used. There might be some high performance engine designs that specify 98RON. But it is the engine design that delivers the high performance, not the energy in the fuel - which is the same. The 98RON is only used to push the onset of detonation further away than could be achieved with 91 or 95.

If the same high performance engine is supplied with petrol with lower RON than specified, then the knock sensors will feedback an earlier point of detonation onset to the ECU, and the ECU will typically retard the ignition timing slightly to prevent detonation, and thus the engine will have reduced performance, and maybe increased fuel consumption. I don’t know this as fact but the ECU might also reduce the turbo boost a little as well.

Cheers.

I sort of get your point about the ECU doing its magic calculations and adjustments.

But, even though I'm probably as avid as you are in dismissing ACA in terms of credibility, I'm not so eager to dismiss Ian Luff, who was also involved in that test.

But my main point/question is, what about in the days before the sophisticated ECUs we now have? Because that's when that test would have been done.

 

[seasink]

The 604 is an oldie, with the big inlet, but can it handle high flow foaming? My old Landie could. Quite a mess if it cannot.

If petrol types vary in specific gravity then different results could be expected. I haven't been able to find figures for 95 and 98.

 

[Richard W]

my main point/question is, what about in the days before the sophisticated ECUs we now have? Because that's when that test would have been done.

Surely in days before more sophisticated ECUs, there would have been less, rather than more, ability for cars to sense and adjust to different fuel? Advance etc would just have been locked at a particular level (ie, no cars able to take advantage of 98, but able to knock the timing back a touch if they sense a lower octane fuel). Therefore there should have been even less reason for a car designed for a particular fuel to do better on a higher octane fuel?

As a lawyer, I may or may not have had to give advice to a fuel company in the past about the legality of selling the same diesel fuel at certain sites with two different prices depending on the pump it was coming out of....

 

[PeterT]

My 1.9L Mi16 was always cheaper to run on 98 than 91, when there was a 10 c/L difference. ie 80c vrs 90c

 

[Whippet]

Surely in days before more sophisticated ECUs, there would have been less, rather than more, ability for cars to sense and adjust to different fuel? Advance etc would just have been locked at a particular level (ie, no cars able to take advantage of 98, but able to knock the timing back a touch if they sense a lower octane fuel). Therefore there should have been even less reason for a car designed for a particular fuel to do better on a higher octane fuel?

As a lawyer, I may or may not have had to give advice to a fuel company in the past about the legality of selling the same diesel fuel at certain sites with two different prices depending on the pump it was coming out of....

Hi.

Yes the big advantage of ECUs is the real time compensation calculations that they perform many times a second. Prior to these you would need to manually adjust the distributor advance setting if the engine was pinging a bit. So you would have needed to only use the RON fuel that the engine needed.

If I owned a fuel company and I could use marketing to sell fuel for a higher price, that was essentially the same fuel with the same cost, and thus achieve more GP, then I would do if for sure.

Cheers.