flotsam

Super unleaded is WELL WORTH the extra expense. As I've posted many times before on these fora (but which have been subsequently deleted), the octane rating is how much you can compress the fuel before "pinking" or "knocking" occurs. High compression engines are supposed to be more efficient like a diesel engine which typically has compression ratios of about 16:1.

An engine with compression ratio of up to 10:1 doesn't need super unleaded. But higher than that and you do.

Modern engines have anti-knock sensors which retard the timing to compensate for too low an octane fuel. A high compression engine can run on ordinary unleaded but the timing is moved away from maximum brake torque.Severe knocking will eventuallly shake an engine to bits.

The Audi R8, for example has a massive compression ratio of 12.5:1 and probably needs about 110 RON fuel to run properly, though it's probably offset by a richer fuel-air mixture!!!. Even on 98 RON super unleaded, it only gets 371bhp and 292.8 lbft of torque according to rototest.com. However, it should get 420bhp and 317lbft of torque.

Here's Tesco Momentum's specifications:

http://www.tescopfs.com/momentum99/specifications

Note the high sensitivity (RON-MON). If, as they say, the sensitivity is normally between 8 and 10, then Tesco Momentum will make your engine run smooth at idle (RON) but will leave your engine feeling no better than 97RON super unleaded when you put your foot down (MON). This agrees with my experience of it.

Tesco claim 2.85% better economy over a range of vehicles and test routes.

Here's Shell V-Power which has an even higher sensitivity but note NO ETHANOL ADDED:

http://www.acetech.com.my/Download/Shell_V_Power_info.pdf

Here's BP Ultimate (95RON):

http://www.bpdrakensberg.co.za/wp-content/themes/kzn/docs/products/TDS_BP_Ultimate_ULP95.pdf

Here's BP ordinary/premium unleaded (93 & 95RON):

http://www.reddyfuels.co.za/products/petrol.php

The only BP ultimate spec I could find was in german showing a better MON thatn Shell/Tesco and 1% ethanol max:

http://www.bp.com/liveassets/bp_internet/bp_ultimate/bp_ultimate_austria/STAGING/local_assets/downloads_pdfs/0_999/produktdatenblatt_ultimate_super_v1_0.pdf

Harvest Energy claim 97RON and maximum 5% ethanol for their super unleaded.

I'm running on Harvest at the moment. Noticed a surge in ooomph straight away and feels like I have to keep my foot OFF the accelerator in 30mph zone otherwise the car will run away from me, as it were. Engine is completely silent (!) but MPG is low or perhaps I'm just putting my foot down. I always thought it was Tesco's ethanol which made my car feel sluggish but Harvest has a maximum of 5% too. Is the difference of 1 MON THAT noticeable (assuming it has a similar spec. to BP who no longer supplies Harvest)?

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Interested to read the thread in the IS area about fuel quality and it made me wonder what other 'F' owners have found to be best.

I've sort of swung towards Sainsbury 97 or Tesco 99 because it seems such a huge output engine to trust to 95 octane but perhaps I'm just paying an extra few pence a litre for the sake of it if the ECU's up to self-adjusting for the lower grade stuff - I don't suppose any of us would moan about dropping a few horses' worth of power if it saves the odd shilling a tankful!

RON ratings. The final test of petrol is done using a special standard single cylinder engine to find the "knock" coefficient. With the best equipment available, it is only just possible to measure RON to within about +/-1.5. So the actual figures at the pumps for petrol rated as 95 RON could be 93.5 to 96.5 & for 97 RON 95.5 to 98.5. But these small amounts really make almost no difference to anything. This does not mean that different petrols with different additives will not behave in different ways. RON has nothing at all to do with the "Power" in the petrol, just in the way it burns. So, most engines with reasonable ECU's will attempt the best fit to what the system thinks the fuel is, but it is only an approximation because they are just not that accurate. This in turn means that a car may best match brand X 97 RON today, but the next delivery is 2-3 RON different, so it is no longer the optimimum choice. So in the end - choose what works for you. For me Sainsburys 97 RON seems fine, but to be fair 95 RON is what I get rather than wait for a pump, and it seems just as good

Errm, to be precise it's not "the way it burns". The RON is how much you can compress the fuel before it self-ignites, like diesel. Diesel engines have a compression ratio typically about 16:1. This is why they're more economical and also why (if well maintained) the engines are stronger.

Modern cars adapt to lower RON with the anti-knock sensor which retards the timing. But this means you're compressing the fuel, even as it's trying to expand, for longer in the cycle. NOT Optimum.

95 RON ordinary unleaded is good for 10:1. My 10.5:1 engine is best on at least 97 RON.

Watch out for ethanol though which is often used as an octane booster. It has 102 RON but has less energy (it expands less when burnt). Another dirty trick by those oil companies.

Momentum 99 is made by Greenergy, whereas Shell seem to blend their own 99 RON forumla for their V-power Nitro+. Shell specify it to be 5% ethanol, but then pretty much all unleaded sold in the UK current does, in order to meet the government's biofuel target. Although Greenergy specify their fuel to contain up to 5% ethanol, their 99 product usually contains less ethanol (usually between 1.5 and 2%). They publish a monthly analysis of their fuels. http://www.greenergy.com/Products_services/test_results/99_octane/99octane_2013.05.pdf

Higher octane fuel generally tends to have a lower energy content than lower octane fuel, but if the ECU is tuned for high RON, then it is possible that you get slightly more performance and slightly better fuel consumption with the higher octane fuel, despite the fact that it is more "dilute". That said, ethanol is much more dilute than "petrol", so a 5% ethanol content will knock about 2% off the energy content of "pure" petrol.

Looking at the figures from my IS250's ECU, which generally only gets fed 95, the ECU does claim to have knocked a couple of degrees off the ignition timing, so it may actually be tuned for 98. I might run a few tanks of 99 and see if the ECU advances the timing, or whether the Euro-spec ECU comes pre-set to the less aggressive timing.

Neither fuel company are particularly forthcoming with regards to their additive package. Shell are obviously aggressively marketing their Nitro+ additive, which is said to be puchased from the additive company lubrizol. However, only an insider would really know, because I doubt that Shell publish what's in it or where it comes from. It wouldn't surprise me if Greenergy buy from the same additive supplier, even if it's not the same product. That said, you can't blame shell from promoting their new additive - a state-of-the art additive may only add 0.05 - 0.1p/l to the cost of the fuel, but can command a price premium of 3p/l (nice profit if you can get it).

Oh, and Greenergy and Shell have recently announced a Joint Venture with regard to revamping a major refinery - wouldn't surprise me if there's a lot of "cross-pollnation" in terms of sharing fuel blends. That said, Greenergy already supply most supermarkets with fuel, as well as many Esso stations.

Suprised!

I've tried Momentum and the engine (compression ratio 10.5:1) though smooth feels underpowered. Sainsbury's super unleaded (which was 97RON last I looked) feels much livelier.

Ethanol has a RON of 102 meaning you can compress it that much more before it self ignites (known as "knocking" or "pinking") and it has less energy; it expands less when ignited. Perhaps the Sainsbury's petrol I've been using has next to no ethanol!!!

I used to dribble water on the car so that you get a sheet of water which runs of as one big mass. But there's a better way,

Do NOT use a chamois for drying the paintwork. Save that for the glasswork only.

Instead, get a damp cloth impregnated with car wax and use that to displace the water as well as apply the thinnest of films of car wax. It's quicker and you get a glossier shine, without streaks.

The RON is a measure of how much you can compress the fuel before it self-ignites; before the spark plugs spark! This is how diesel engines work, which have a higher compression ratio of typically 16:1 and why they're stronger engines.

Petrol engines can get the same effect. It's called "knocking" or "pinking" and will, in time, shake your engine to bits.

Anti knock sensors roll back the timing, meaning they ignite the fuel earlier (I believe). But this means you're compressing an expanding fuel.

Petrol cars with a compression ratio of up to 10:1 are OK with standard 95 RON unleaded. But my 10.5:1 engine needs 97 to run at its best.

Clouding the issue is ethanol which has a RON rating of over 100 so is used as an octane booster. Unfortunately, it doesn't expand as much when burnt so isn't as economical. It can also corrode some components of your fuel system.

Ceremony of the Keys? Stuff that!

Oh dear.... yet more dodgy dealers... what is happening to Lexus these days? BMW haven't bought out all the dealerships have they?

Can't imagine why.

Friendly and professional. Top quality service and at a very reasonable price. Excellent!

Cross your fingers and hope they don't change the staff.

Agreed with what is been mentioned, but I believe in most of the lexus car manuals it is mentioned a minimum octane of 95.

Yeah, as I said, it retards the timing so that your car CAN run on 95 but it runs far better on higher octane if it's a higher compression engine.

The handbook says every 63,000 or six years.

If it's been serviced at Lexus, they may have records of your car's history.

Hi some members really do make you laugh or is it cry???????does anything really surprise us anymore????wonder whats next.

The last laughs on you. I make a living off how the government rips suckers like you off.

Toyota actually put right some of the damage done by dodgy garages on my car.

OK I've checked the work and as far as I can tell it's OK.

I've been using them for a few years as I DID like the work they'd done.

Perhaps I WAS being paranoid. But I still can't see how 6 litres of oil goes into an engine spec'd at 5.6 litres.

So it looks like I owe Toyota a full apology.

I've checked the oil too and it does seem to be the fully synthetic 0W-40 I supplied.

I've taken the car out for a spin.

Amazingly, it's smoother. This I noticed after each service for the first few years after I bought the car, but in subsequent years there seemed to be no change after servicing. The cold idling revs have also returned to 800, whereas they shot up to 1200 after Lexus Hull changed my cam belt a few years ago. This just begs the question, what did Toyota put in my car the previous time when I had them service it too and Lexus other times? Last time, I asked for fully synthetic and Toyota said OK, but when I got the invoice it said part-synth 5W-30.

Also, NONE of the garages Lexus or otherwise have done the full service according to the hand book. The closest was Lexus Hull where the invoice claims they've done coolant and spark plugs which no other garage claims to have done and I should have had brake fluid, differential and transmission oils changed by now. So who's ripping me off, Toyota or their franchised garages? Or is Toyota being pedantic and the garages are saying it doesn't need to be done? That's the claim of some other posters here. The Mitchells Repair, which seems to be american, offers a slightly different schedule too!

Furthermore, the handbook says, just use any API SJ oil. But the Mitchells Repair manual says it must be synthetic. Speaking to Lexus in the UK, they say use 5W-30 as 0W-xx would be too thin. But xxW-40 IS thicker. In other words, compared to a 0W-30, a 0W-40 is like a woman, cold when thinner, but thicker when hot.

When the engine's up to temperature, who cares about the environmental temperature? So why is Castrol Australia recommending an 0W-40 whilst Castrol UK only recommend 5W-30 for my car? Wouldn't 0W-30 be better?

For cars other than in Germany, the handbook says idle for 10 seconds before driving off. This implies you need to get oil to the cams which are overhead and perhaps a 0W-xx oil would be better when cold and when most of the wear occurs. Even then, at 20°C, you're looking at about 500cst which is really thick. Why would you want it any thicker? That might also explain why my cold idling is now back at 800rpm. Some online forums claim any xW-40 would have the same "thickness" of 14 centistokes (viscosity) so should be fine and also agrees with the OHC issue saying it will be better for reducing wear than a 5W-xx.

The only remaining issue is cooling, which Amsoil claim the oil is responsible for 40% of, while the coolant the other 60% and a thinner oil is better.

I've already found out, for example, that although the handbook says 95RON petrol is OK, that 97RON means the timing isn't retarded for anti-knock for any engine with compression ratio greater than 10:1, so will run smoother and maybe even more economically than 95RON. This seems to be a big secret in the industry.

Is there any advantage in running my RX on Super Unleaded fuel. I imagine a knock sensor would make any neccessary adjustments to the engine, but would it help performance/fuel consumption in any way???

ALWAYS USE SUPER UNLEADED.

If my memory serves, the RX has a compression ratio of over 10:1.

97 RON fuel self ignites at a higher compression ratio than 95 RON.

Your car can compensate for 95 RON with its anit-knock sensor, but it does this by backing off the timing. This is less efficient; the whole idea of high compression!

Normal unleaded isn't "watered down".

95 RON self-ignites at a lower compression than 97 RON which is what Japan uses. This is how diesel engines work; by self-igniting; no spark plug.

If your engine has a compression ratio of about 10:1 or higher, you need the higher RON "super" fuel. Otherwise, the engine will compensate with its anti-knock/pinking sensor and back off the timing. The whole idea of a higher compression is greater fuel efficiency. But if the timing is backed off it loses this advantage.

Fifth Gear showed a Subaru Imprezza makes full use of super unleaded and gained several percent in power and torque.

Super unleaded DEFINITELY gives more power, torque and economy as well as a smoother engine. The RON rating refers to how much you can compress it before it self-ignites and so should be matched to compression ratio. Diesels have compression ratios approaching 20:1!!!

If you put crappy 95 RON in your 10.5:1 engine, it will tend to self-ignite, causing knocking and damage to your engine. To offset this manufacturers install a knock-sensor which retards the timing, but really kills the performance.

All explained here:

www.daytona-sensors.com/tech_tuning.html

This article suggests a MINIMUM of 98RON for a 10.5:1 engine.

In the past I have tried BP ultimate and Shell optimax in my 97 2.2 Prelude vtec, and I could never feel or see any difference in either consumption or performance.

I have done the same with the GS300 Sport, and yet again I could see no improvement, however over the past month or so when filling up I have been swapping between full tanks of Unleaded and Super Unleaded, and i'm now convinced that Tesco Super Unleaded gives me better performance and mpg.

Has anyone else experienced the same?

No.

Super unleaded DEFINITELY gives more power, torque and economy. The RON rating refers to how much you can compress it before it self-ignites and so should be matched to compression ratio. Diesels have compression ratios approaching 20:1!!!

If you put crappy 95 RON in your 10.5:1 engine, it will tend to self-ignite, causing knocking and damage to your engine. To offset this manufacturers install a knock-sensor which retards the timing, but really kills the performance. If you haven't noticed a difference, there's something wrong with your engine or the petrol or you have a low compression engine.

All explained here:

www.daytona-sensors.com/tech_tuning.html

Hi,

The other thing to remember with the TT Soarer is you will have to run it on Super unleaded fuel or you might find the engine pinking ;)

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With all due respect ... this is patently untrue - in fact it's complete rubbish!

With adr it is not complete rubbish.

The RON rating should be matched to the compression ratio.

See:

www.daytona-sensors.com/tech_tuning.html

and all will be explained.

Some T*** crashed into the back of me.

I claimed and Privilege failed to sue the T***. Instead I found the T***s insurance company was claiming against me. Initially, they didn't even give me a claim form. They gave me BS about not being able to find a lawyer. Then I was told I had the right to choose a court. Then I found the court was 200 freakin' miles away and that I'd been refused the court in the town I'd asked for. To this day, I still don't know what the verdict was, but I had to pay my xs. It's obvious they had no intention of even bothering to do the work they'd been paid for.

Privilege, Churchill, Direct Line et al. are part of Royal Bank of Scotland which is now in the crapper.

Fred the Shred is a piece of S***!

Some T*** crashed into the back of me.

I claimed and Privilege failed to sue the T***. Instead I found the T***s insurance company was claiming against me. Initially, they didn't even give me a claim form. They gave me BS about not being able to find a lawyer. Then I was told I had the right to choose a court. Then I found the court was 200 freakin' miles away and that I'd been refused the court in the town I'd asked for. To this day, I still don't know what the verdict was, but I had to pay my xs. It's obvious they had no intention of even bothering to do the work they'd been paid for.

Privilege, Churchill, Direct Line et al. are part of Royal Bank of Scotland which is now in the crapper.

Fred the Shred is a piece of S***!

Some T*** crashed into the back of me.

I claimed and Privilege failed to sue the T***. Instead I found the T***s insurance company was claiming against me. Initially, they didn't even give me a claim form. They gave me BS about not being able to find a lawyer. Then I was told I had the right to choose a court. Then I found the court was 200 freakin' miles away and that I'd been refused the court in the town I'd asked for. To this day, I still don't know what the verdict was, but I had to pay my xs. It's obvious they had no intention of even bothering to do the work they'd been paid for.

Privilege, Churchill, Direct Line et al. are part of Royal Bank of Scotland which is now in the crapper.

Fred the Shred is a piece of S***!

Lowest quote is 433 from Privilege... I was paying £408 fully comp on my 53 plate IS200 LE

You pay for what you get.

Some T*** crashed into the back of me.

I claimed and Privilege failed to sue the T***. Instead I found the T***s insurance company was claiming against me. Initially, they didn't even give me a claim form. They gave me BS about not being able to find a lawyer. Then I was told I had the right to choose a court. Then I found the court was 200 freakin' miles away and that I'd been refused the court in the town I'd asked for. To this day, I still don't know what the verdict was, but I had to pay my xs. It's obvious they had no intention of even bothering to do the work they'd been paid for.

Privilege, Churchill, Direct Line et al. are part of Royal Bank of Scotland which is now in the crapper.

Fred the Shred is a piece of S***!

Doesn't ethanol damage engines?

Read "The Great Ethanol Scam" by Ed Wallace on Business Week Online.

On Jan. 16 of this year, Lexus ordered a massive recall of certain 2006 to 2008 models, including the GS Series, IS and LS sedans. According to the recall notice, the problem is that "Ethanol fuels with low moisture content will corrode the internal surface of the fuel rails." In layman's terms, ethanol causes pinpoint leaks in the fuel system; when leaking fuel catches your engine on fire, that's an exciting way to have your insurance company buy your Lexus. Using ethanol will cost Toyota untold millions.