Fuel. 87 Octaine Vs. 93 Octaine.?

Question

Over the years I've driven cars with high performance engines (Ford's 5.0 and Chevy's 5.7)

The Ford's handbook settled for 87 Octaine, while the Chevy's handbook for the Vette specified only 93 Octaine.

Why? The Vette's engine is more powerful to a degree, but they're both very powerful.

When does using 93 become mandatory (or highly recommended)?

I understand the workings of it.. my question is why would the 2 vehicles (being almost identical in power) require 2 different levels?

Answer 1

it's all about the engine's compression. the 'stang is most likely pushing 9.5/1 while the 'vette "cheats" to get the hp by using a bigger piston most likely 10.5/1 or maybe evel 11.0/1

Answer 2

Hi The higher the octane rating is the more resistance there is to engine knock . 93 octane has a higher resistance than 89 octane. Since you have driven high performance cars before I'm sure you know it also depends on many factors such as timing ,comp ratio etc etc. 89 octane has 89% isooctane and 11% heptane which are a few of the ingredients that make up gasoline.Hope this Helps to answer your question. You CANNOT compare a Chevy to a Ford motor or visa verse , they are two different types of motor's and each one has there own unique features.Higher octane burns faster,I would say you have to check out the exact specs of the motors.especial the cylinder heads and quelch area in the combustion chamber of the heads if all else seem's equal.One motor needs a faster burning fuel than the outher which is higher octane.

Answer 3

Sir. The overall shape of the combustion chamber and the compression ratio combines to offer the need for a specific octane of fuel. Some engines with a 10 - 1 compression ratio can live on 87 octane. A Corvette for example is tuned with an aggressive electrical advance curve to fire the spark plugs. the fuel injection system is tuned to aggressive camshaft timing, lift and overlap. The intake valves open sooner and the lift of the valves are wider from the valve seats. The valves open quicker to their maximum lift and remain open for more degrees of camshaft / crankshaft rotation and close quicker. This is due to the roller hydraulic cam lifters. The lobe centers likely are closer. All these things are screaming for 93 octane fuel. The lower octane fuel may knock ping and hammer because the onboard knock sensor can't control the pre-ignition of the fuel.

Answer 4

High compression ratio engines require high octane gasoline to reduce detonation. Detonation is when the fuel/air mixture in the cylinder ignites before the spark plug fires. This happens when the fuel/air mix is compressed by the piston. The higher octane gasoline has a slower flame propagation (it burns slower) so this reduces the chance of detonation (knock or ping.) The extreme of this is in diesel engines, which have compression ratios in the 40 to 1 range and do not need spark plugs. The fuel/air mixture is ignited by compressing it to the point where the heat in the mixture causes it to burn.

Answer 5

The diferences of octanage cause a variation of temperature and timing of explosion inside the combustion cam. When an engine is engeneered and tested they look for the best combinations to reach the wanteds results and considering the engine limits. Thats why you find diferent octanages available at the gas station.

Answer 6

Higher compression engines require higher octane gas to reduce pinging

Answer 7

it depends on the compression ratio of the engine. a car with a higher compression will need a higher octane fuel to avoid detonation.

Answer 8

the higher the compression and faster ,,more timing require high octane to stop knock. Iron heads on same motor require more octane then Aluminum heads.