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I started a thread on this 3 years ago on the IS250 forum called supermarket petrol good or not so good. It attracted quite a few comments and is worth a read IMO.

Unfortunately I'm not clever enough to paste the link to it despite trying!

The conclusion I've drawn is that whilst all petrol meets the standards required, the premium fuel may give slightly better mpg and may be "better" for the engine. There are also plenty of examples of cars reportedly running better on premium fuel, but I've not read anywhere of cars running better on lower grade or supermarket fuel.

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I used to think that Shell V-Power or similar brands of high-octane fuel might yield a combination of better economy

and performance but have never found objective proof of it.

As regards performance, I liked to think that the 300h accelerated better and was generally perkier in its responses,

but have concluded that clever advertising claims may well have been fooling me into pampering the car, of which I

am very fond, with "better" fuel in much the same way as premium-priced pet foods are supposed to give your dog

a wetter nose and your cat a glossier fur. As regards economy, I occasionally make motorway journeys of 1500km+

on identical routes with fewer variables of speed, traffic etc., than you might get in everyday motoring. On the couple

of occasions when I started out with tankfuls of V-Power I found myself pulling into exactly the same filling station as

I customarily did with normal petrol. In other words, after 900km or so the V-Power did not get me to the next filling

station 50-60km further along the route as I hoped it might. Certainly, I may have needed to put a bit less petrol into

the tank but, if I did, the amount was nowhere nearly sufficient to have justified the price difference.

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I use premium fuel in my Ducati because in my mind it does improve the running of the engine. I do not do many miles a year so the extra cost is minimal. Would not be able to justify putting it my lexus even if it did get me to the next traffic jam faster.

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  • 3 weeks later...

premium-priced pet foods are supposed to give your dog

a wetter nose and your cat a glossier fur.

Non premium cat food 4% meat or premium cat food 60 to 90% meat. Cats are carnivores so have to eat meat. What would you feed your cat? I avoid supermarket fuel if possible preferring BP Esso or Shell. Tesco had to replace a few engines due to some contamination not that long ago.

Ed :innocent:

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I've never used 'premium' fuels in any of my previous cars, and have never had any problems. Not even on a tuned 3L twinturbo in-line 6 that dynoed at 380bhp. Higher octane fule gives you more knock protection, and better controlled detonation, neither of which matters on the IS300H. If your really want a bigger 'bang' methanol injection is what you want, better cooling, more controlled detonation, but your need be prepared to carry a boot full of methanol...Again not relevant for the IS300H.

Petrol is petrol, and advertising clearly works, which is why so many people presumably think BMW/Audi etc are some how 'superior' to a Ford or Toyota :)

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My first job, many decades ago, was as a trainee in the Supply & Distribution department of a major oil company which

shall be nameless. Whenever any of our filling stations were at risk of running dry and we were unable to supply them in

time, we simply contacted one of our competitors to help us out by sending tanker trucks of their own and would return

the favour when they themselves had a similar problem. In other words, not all customers were putting a Large Striped

Cat in their Tank all of the time while others sometimes did without knowing it. This was in France and Benelux but

I think it happened everywhere in the world. No doubt advertising ethics have improved since.

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I'd rather 4% meat in my petrol than 60-90%!

Completely different example, clearly there is a benefit with quality cat food, "premium" petrol seems to be more a marketing ploy, I have tried both and never found much if any difference, I have also not seen any tests by magazines etc clearly shouting about the benefits, if premium was much better, why are car manufacturers not recommending it ?

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I'd rather 4% meat in my petrol than 60-90%!

The cat loves premium!! It makes the emissions from the rear less pungent to. :yack:

VW did a premium fuel test which did produce more bhp in a Golf. Not that VW would ever cheat in a test now would they.......

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I use one of those miracle magnets around the fuel pipe and a vortex generator in the air intake - these give really good results in terms of performance and economy. I am being skeptical, of course, but my point is that what people report is often their perception and might not be substantiated under controlled laboratory conditions. Those miracle devices that were all the rage a few decades ago were shown to be absolutely worthless but that didn't stop thousands of people reporting miracle results. There may be benefits in using premium fuel but it is probably small and, in my view, would need to be demonstrated under controlled conditions to make it a worthwhile additional cost to what is already an expensive activity.

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On another forum someone posted that they were getting much better mpg with premium fuel, to back up their argument they even posted their figures, when analysed properly, their was no significant difference, any gain seemed to be because when using day to day they used supermarket fuel, only using"premium" fuel on long trips which would give better figures anyway.

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VW did a premium fuel test which did produce more bhp in a Golf. Not that VW would ever cheat in a test now would they.......

You CAN get more BHP from using higher octane fuels (V-power etc), but you need adjust the timing on the combustion cycles to take advantage...ie: Tell the engine to advance/retard the ignition because your confident the higher octane fuel is more stable under pressure and has less chance of uncontrolled detonation - which can can cause damage to the piston head (knock). Most turbocharged 'Performance' petrol engine can do this to a degree, there are also various third party options for you to change the timing/map of the car if your going to be 100% of the time running higher octane fuel. But on the whole most petrol engine are designed to run at a set operating premature, you can go and pour in some of the stupidly expensive 102 octane BP ultimate fuel, and in 99% of cars your get no increase in performance.

On the IS300H it's 100% pointless, the whole hybrid setup system is geared towards economy, and locked down tighter than Donald Trump's mansion in Palm Beach during Ramadan :).

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On the IS300H it's 100% pointless, the whole hybrid setup system is

geared towards economy, and locked down tighter than Donald Trump's

mansion in Palm Beach during Ramadan

It is not specific to Lexus or the IS300h though as hardly any cars that use regular unleaded can advance their timing beyond the normal range to take advantage of premium fuel. Do we know for sure that the IS300 cannot advance its timing though? Some cars can from what I understand :innocent:

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The drive train from the IS300H originated in the Prius, I would be amazed if Lexus/Toyota spent time running the drive train to increase output based on fuel grade. I could be wrong, the only real way to tell is to stick the car on a dyno - but the hybrid system will cause with the dyno since 'revs' in the IS300H really have no meaning. There's a local garage whom I've used a few times for dyno runs at £40 a go, one day if I'm ever bothered I might ask them to stick the IS300H on and see what happens :)

If you want to use 'premium' fuel go for it, but just don't be under-illusion that it's some how it'll offer any objective benefit, apart from helping the petrol companies keep their profits up....Which they will no doubt welcome given the way oil prices are sliding.

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Any car can be forced to relearn its timing by resetting the ECU. Disconnecting the Battery or removing the EFI fuses for a few minutes will usually achieve this. The timing and fuelling trims will then be defaulted and the ECU will go through a relearning phase for the next few miles. If you perform this reset after putting in a premium fuel then it could result in increased performance if the ECU has been programmed that way (to advance timing just prior to the onset of knock).

However in the case of the IS300h I suspect everything is setup around economy so you won't see any benefits with premium fuels.

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However in the case of the IS300h I suspect everything is setup around economy so you won't see any benefits with premium fuels.

Speculation.

The IS300 in sport mode is not particularly economical.

I am not convinced premium fuels make any difference but nobody knows for sure.

Ed :flowers:

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^^ The IS300H has as much 'sporty/performance' credential as a Prius. Rember the TopGear episode where a V8 M3 managed a better mpg than a Prius around a track??

Sometimes in life it's worth paying extra, but 'premium' fuels isn't one of them. But the cost difference isn't that much though, so for placebo effect and making your self feel better than its no harm done....There are plenty of other ways to waste money.

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Rember the TopGear episode where a V8 M3 managed a better mpg than a Prius around a track??

Yes I remember it, they drove a Prius flat out at over 100mph around a test track and then said a V8 M3 which is designed for driving at 150mph on the German autobahns had better mpg. An entertaining film but deeply flawed. I would not have thought anyone actually believed it!!

The IS300h may not be a sports car as such but it has better acceleration than other cars in its segment. It has good road holding particularly in Fsport guise which also has a stiffened sports suspension. It certainly looks sporty.

I once owned a 2 seater soft top sports car which was fun but it wasn't particularly fast but it didn't need to be.

I drove home late last night through the back lanes and my IS300h Fsport was definately fun in sport mode and to hell with the MPG!!

Ed :flowers:

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