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The fuel type is closely tied to the engine compression ratio. So having low quality fuel will give it more pressure and causes piston slapping. This will cause engine cause knocking noise. But your car (if modern) has knock sensor that can detect this condition and adjust. However, if you abuse this, the knock sensors will usually go out and you would have to replace it. So I would say yes – use premium gas unless your knock sensors are dirt cheap and easy to replace.
Fuel supplies also adds different additives based on the seasonal change. So if mid grade gas my work during the summer, but it may cause problems in the winter.
The question I usually ask when confronted with the regular vs. premium debate is wouldn’t you be willing to pay an extra $3.20 for a product you like better (i.e. beer, pizza, etc.)? Then why aren’t you willing to pay an extra $3.20 to fill your car with a tank of premium (assuming $0.20 X 16 gallons). If your car says “premium only” then buy “premium only.” It’s a no-brainer.
“Premium” gasoline is of no higher quality than other gasoline. The difference is in octane rating, a measurement of the fuel’s resistance to combustion. Here’s a secret that few youngsters seem to understand. (As a substitute teacher, I teach high school auto shop sometimes, so I know this one baffles beginners.) Compression (or pressure) creates heat. Spark plugs (and glow plugs) are not necessary for combustion.
Yes, Virginia, there are gasoline engines that run without spark plugs (Homogeneous charge compression ignition or HCCI engines) and there are diesel engines that have no glow plugs (they are hard to start. Glow plugs assist in starting a Diesel, BTW. They shut down seconds after the Diesel engine starts.)
How much heat? In a diesel engine (with a typical compression ratio between 18 to 22 to one) the air entering the combustion chamber reaches over 800 degrees Fahrenheit on the compression stroke. Diesel fuel is injected into the combustion chamber on the power stroke and is ignited by that very hot air.In a gasoline engine, the fuel and air mixture (homogeneous charge) is superheated by pressure (the compression stroke) and is on the verge of combustion when the spark plug adds the additional heat needed for combustion.
This is why you have different fuels for different compression ratios. An engine with a high compression ratio will heat the charge to a higher temperature than an engine with a lower ratio. This means the gasoline for the high compression engine needs to have greater resistance to combustion. In other words, it needs to be capable of reaching a higher temperature without igniting by means of heat alone.
You need to match the fuel to the compression ratio. You need to match an engine which generates X amount of heat on the compression stroke to a fuel that can withstand that heat and “wait” for the spark plug to fire.Steebs, To answer your question, Do you have to use premium in a car when Premium is recommended? Yes… and no.
Back in the day before electronic sensors and controls, when cars had mechanical distributors and 4 barrel carburetors the size of toilets, you needed high octane fuel for high compression engines and if you didn’t use it, you would damage the engine. The engine would protest with noises variously called “knocking” or “pinging” which sounded like the same noise to some us, but the truly stuck-up among the grease monkeys insisted they could hear a difference. I recall I could tell the difference, but nowadays I can’t even remember which term applies to which condition. Anyway, the Bench Racers would smoke their Camels and jaw about red hot exhaust valves and pre-ignition and the young mechanics would commence with an actual diagnosis.
If you have an old gasoline vehicle and it sounds like an old diesel, something is not right; wrong octane fuel, ignition timing advanced too far, carbon deposits inside the chamber that heat up red hot, Communists under the bed…
New vehicles with high compression employ electronics that will detune the engine when you use fuel with low octane rating. There is even a Porsche (or was a couple years ago) that was intended to run fuels of different octane ratings. This was a normally aspirated flat six rated at well over 100 hp per liter, more horseponies per liter than anybody else got out of a liter! My Porsche enthusiast friend told me about it claiming Porsche engineering was superior to anybody else’s and he loaned me a car magazine with an article about the car. I read the article carefully. The Porsche was running compression of 13 or 14 to 1! You could obtain race gasoline at a track to match the high compression ratio, but Premium gasoline from a real world gas station could be used ordinarily as the car would sense it and de-tune. This means the horse ponies would disappear and the gas mileage would drop.
This is why you should run the recommended gasoline for your car if Premium is recommended. You will save no $ running cheaper lower octane. The engine will not run efficiently when your electronics take over and de-tune it behind your back.Great job yarddog!T)
Also I believe they say to run only high octane fuel in all turbo vehicles.., I do anyway just cause the car feels and drives better.
But turbo engine are lower compression ratios, so what is your input on that yarddog?
This is a great thread so far.I haven’t owned or worked on any late turbo engines, but I would imagine there would be greater risk in using lower octane fuel with a late turbo engine even if it is able to de-tune.
I’d like to know some more details about the latest direct injected turbocharged engines. It seems to me that they would be able to run more boost without damage. With direct injection, you could inject gasoline on the power stroke as well as the intake stroke.
Ford has a line of engines they call Eco-boost featuring direct injection and turbo charging. There’s an Eco-boost V6 available for the Ford pickup that’s getting very good reviews from the automotive press.
The first engine with direct injection and a turbo was the Alfa Romeo 1750 4 cylinder which is about 6 years old now. It makes about 250 foot pounds of torque and around 235 hp. Alfa (Fiat) has announced they have a new 1800 4 cylinder making 297 hp. They haven’t mentioned a torque rating and they haven’t said the engine is all new or if it’s based on the 1750, but they did say it will be used by Chrysler as well as Alfa. I think they will reveal the engine in a month or two. It should be the cutting edge in turbo technology if Fiat Powertrain gets it right.
I’d be willing to bet that the other manufacturers will follow Fiat and Ford’s footsteps within the next few yearsThanks for the compliment, Trcustoms.
You know a turbocharged engine (with a lower “nominal” combustion ratio compared to a typical non boost engine) will create more combustion pressure under boost. So if you add boost, you increase the pressure and temperature of the charge, so you need higher octane and some enrichment of the mixture.
An engine’s compression ratio number is called “nominal” meaning that the number is merely a name. If I recall correctly, the actual compression ratio (and the resultant pressure/temperature) will change with RPM and with the cam profile. This is why a performance camshaft with greater duration and lift and overlap will benefit from an increase in the nominal compression ratio.
This is why I think the latest advances in direct fuel injection technology will lead to big improvements in turbocharged gasoline engines; smaller engines making the hp and or torque of bigger ones with lower fuel consumption and reduced emissions and CO2.
I have a 2004 Acura RSX with a 2 liter rated at 160 hp. The VTEC system yields 80 hp per liter on 87 octane gasoline, lots of hp per liter, but you would need more displacement or boost to raise the torque.Definitely use premium fuel if the car recommends it. Pre-detonation will occur if you use too low of an octane, which is not good for an engine at all. I had a 03 Cavalier with the 2.2 Ecotec, got noticeable better fuel economy with premium. So it basically paid for itself, that and it only cost $3 more per tank to fill with premium over regular. It called for 87 octane but it had a 10.5:1 compression ratio so premium definitely worked better.
Quoted From yarddog1950: An engine with a high compression ratio will heat the charge to a higher temperature than an engine with a lower ratio. This means the gasoline for the high compression engine needs to have greater resistance to combustion. In other words, it needs to be capable of reaching a higher temperature without igniting by means of heat alone.
You need to match the fuel to the compression ratio. You need to match an engine which generates X amount of heat on the compression stroke to a fuel that can withstand that heat and “wait” for the spark plug to fire.That’s a great explanation yarddog.
As for Fiat/Alfa engine – I hope it receives a better welcome than the Cinquecento. At this rate my grandkids will be old when Alfa finally comes back to the States.
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