Premium Gas Only

[AustinGT]

My friends and family give me a hard time for always putting premium in the LS (although in CA it is the crappy 91 octane with all those stupid emissions additives). I can tell a difference in the smoothness of acceleration and in responsiveness, and although I haven't measured the mileage back to back, the one time regular was put into my tank (not by me!), my average city mileage dropped from about 17.5 to 16.5. To me, paying an extra $2-3 per fill-up is well worth the peace of mind and whatever performance gain can be had... just my two cents!

[lexusontario]

Pemium gas burns slower than regular gas. Since most cars these days bmw lexus accura are high compression engines engineered to run on high test gas ,thus being able to advance the timing, giving more power. By ignition happening with the fuel under higher pressure= more hp more effient burn.

Premium fuel also has morer additives and detergents in it (you get what u pay for) to help keep the fuel systems and intake sysyems cleaner.

When i was chatting to my BMW mechanic he said he had a 3 sereis in that they had to remove the throttle body and clean it to get the car to run properly, the throttle body was coverd in the varnish you get from running regular fuel

[aarman4]

Pemium gas burns slower than regular gas. Since most cars these days bmw lexus accura are high compression engines engineered to run on high test gas ,thus being able to advance the timing, giving more power. By ignition happening with the fuel under higher pressure= more hp more effient burn.

Premium fuel also has morer additives and detergents in it (you get what u pay for) to help keep the fuel systems and intake sysyems cleaner.

When i was chatting to my BMW mechanic he said he had a 3 sereis in that they had to remove the throttle body and clean it to get the car to run properly, the throttle body was coverd in the varnish you get from running regular fuel

***Octane rating has no direct impact on the deflagration (burn) of the air/fuel mixture in the combustion chamber. Other properties of gasoline and engine design account for the manner at which deflagration takes place. In other words, the flame speed of a normally ignited mixture is not directly connected to octane rating. Deflagration is the type of combustion that constitutes the normal burn. Detonation is a different type of combustion and this is to be avoided in spark ignited gasoline engines. Octane rating is a measure of detonation resistance, not deflagration characteristics.***

Not sure where you heard that premium burns slower than regular, but it is not true. Higher octane fuel resists "autoignition" more.

[paulo57509]

I would also add that high octane fuel doesn't burn hotter than low octane fuel.

[SRK]

Thank you Aarman and Paulo for those factual responses.

I remain amazed at the amount of myth and hyperbole that follows this thread. Engines don't "know" that they are luxury car engines, and don't worry about our personal perceptions of what constitutes an appropriate fuel. They react, as designed, to the fuel used and under the conditions present during that use. All else is vain conjecture. The idea that as the car is expensive, one should use expensive fuel, does not follow nor is it supported by the technical facts. Carbon formation is the result of mixture ratio, which remains the same regardless of octane - that's what the O2 sensors are for. People still like to buy things that are expensive thinking that expense relates to "quality". Probably they should drive a Rolls and wear a Rolex. All fuels, low or high octane, are among the most highly controlled substances produced in large quantity in the world.

As for a BMW throttle plate being gummed up with fuel "varnish"? I don't think so. Throttle plates are contaminated with crankcase blow-by mostly, and some BMW engines have a lot of that. EGR systems also contribute - and octane isn't a factor even then.

[lexusontario]

wow i m not really sure where some of u get your perceptions from, but if you want to believe them go ahead. If you spend sometime you will find out that high octane fuel really does burn at a slower rate . Hey check the net!!! if you don't believe me. I have worked on many gasoline engines being a mechanic , and if you dont think that motorcycles ,ones that dont have EGR systems, dont get varnish build up on the intake, hey believe what u want.

Sure dont know why the petrolium industry adds more detergents and cleaners to high octane fuels . Hey forget about fuel injector cleaners too, there all scams also, to grab your money. Good thing engineers figured out knock sensors for you guys ,so u can run regular in your engines , when they tell you to use premium oh yeah just a scam to get your money.

And I never said octane was a factor in the intake getting varnish build up i was saying regular fuel has less cleaners in it than premium fuel.

Wow you like reading thing in.

Enjoy running your REGULAR Grade gasoline.

[aarman4]

wow i m not really sure where some of u get your perceptions from, but if you want to believe them go ahead. If you spend sometime you will find out that high octane fuel really does burn at a slower rate . Hey check the net!!! if you don't believe me. I have worked on many gasoline engines being a mechanic , and if you dont think that motorcycles ,ones that dont have EGR systems, dont get varnish build up on the intake, hey believe what u want.

Sure dont know why the petrolium industry adds more detergents and cleaners to high octane fuels . Hey forget about fuel injector cleaners too, there all scams also, to grab your money. Good thing engineers figured out knock sensors for you guys ,so u can run regular in your engines , when they tell you to use premium oh yeah just a scam to get your money.

And I never said octane was a factor in the intake getting varnish build up i was saying regular fuel has less cleaners in it than premium fuel.

Wow you like reading thing in.

Enjoy running your REGULAR Grade gasoline.

Personally, I only run premium(91-94 octane rating) in my Lex because I step on the throttle quite regularly to pass. I purchase the premium for several reasons... It is recommended by the manufacturer of the equipment I drive......The 1UZ-FE engine is a high compression engine, and the premium fuel resists pre-ignition and 'dieseling' which can happen in a high compression situation.....

Ignition is meant to occur via spark just a few degrees after TDC after the compression stroke of the cylinder. The fuels which have a lower octane rating (87 for example) have the possibility of igniting because of the pressure created during the compression stroke, which results in a knock as the explosion momentarily fights the rotation of the crankshaft and in some cases pushes the cylinder to early. This effect has nothing to do with lower octane "burning faster", it just begins it's burn earlier.

As for throttle body gumminess and what not, I cannot comment as I have never experienced any of that due to gasoline choice.

[Sanpete]

While it's possible that some high octane fuel burns more slowly, the octane rating isn't a measure of that and it isn't why higher octane fuels are advantageous.

It used to be that some gas brands advertised more additives/detergents for their premium fuel, but that's not common now. Not sure how different premium fuels are anymore, apart from octane rating.

[scottmcc]

Thanks for the education, Learn something new everyday..

Using a fuel with a higher octane lets an engine run at a higher compression ratio without having problems with knock. Actual compression in the combustion chamber is determined by the compression ratio as well as the amount of air restriction in the intake manifold (manifold vacuum) as well as the barometric pressure, which is a function of elevation and weather conditions.

Compression is directly related to power (see engine tuning), so engines that require higher octane usually deliver more power. Engine power is a function of the fuel as well as the engine design and is related to octane ratings of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be forced into the combustion chamber. At partial load, only a small fraction of the total available power is produced because the manifold is operating at pressures far below atmospheric. In this case, the octane requirement is far lower than what is available. It is only when the throttle is opened fully and the manifold pressure increases to atmospheric (or higher in the case of supercharged or turbocharged engines) that the full octane requirement is achieved.

Many high-performance engines are designed to operate with a high maximum compression and thus need a high quality (high energy) fuel usually associated with high octane numbers and thus demand high-octane premium gasoline.

And no this did not come out of my head, you can thank google for this info...