flotsam

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About flotsam

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    Advanced Member

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  • First Name
    Samantha

Profile Information

  • Lexus Model
    LS400
  • Year of Lexus
    1998
  • UK/Ireland Location
    Please Select
  1. Hope this wasn't Inchcape Retail, Farnborough on Elles Road. They're worse than Lexus Hull. Not only are they cowboys, they're crooked cowboys. The botch job they did to my car has had to have endless repairs to the botched repairs they did, including things they shouldn't have been touching whatsoever. Complete low life.
  2. According ot the tests, my LS400 mkIV is 67.5dB at 60mph. In other words, it's all tyre noise.
  3. Here's my mpg in mkIV LS400 passing the same point on cruise control, which has a VERY slight incline (as I didn't want a coasting mpg), almost flat. Notice how Lexus has set it up for 56mph: mph mpg 40 42 50 42.7 55 44.4 56 47.2 57 42.9 59 41.1 60 39.7
  4. 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)?
  5. Supermarket Petrol

    spam
  6. Fuel Choice

    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.
  7. 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!!!
  8. Hello / Car Washing Problems

    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.
  9. Premium Petrol 'is A Rip-off'

    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.
  10. 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.
  11. Mk4 Ls400 Cambelt

    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.