octane rating and engine performance
In Texas, the minimum octane rating is 87. On a recent trip to Glacier, I noticed a lot of the fuel in states like CO, WY and MT, the octane was 85, and you had to buy the mid-grade to get 87 and abov...
Forum Discussion
4x4ord wrote:ShinerBock wrote:
Here is a good video about the effects of running two different octanes in the same engine at the same time.
Dyno Testing Premium Fuel - Octane Level vs Performance - Shell V-Power
Notice how fast and often the engine is constantly adjusting timing as I stated earlier. It is even adjusting each cylinder to have its own timing depending on knock in that cylinder. BTW, VW recommends 87 octane for that car, but states that it has the ability to adjust performance on higher octane fuels as you can see in the video
That is an interesting test. So a VW owner should expect to gain 4% in fuel economy by choosing 15% more expensive fuel. I wonder how heavy the load was on the engine during the test?
The 4% increase was cylinder pressure(torque/power) and I am not sure if that correlates into the same percentage in regards to efficiency. I am also not sure what load or rpm the 4% pressure increase was at, but it did go up past 7% after he was done talking. From the sound of it, the engines was not revving that high when it reached a 7% pressure increase, and I know the pressure gains will generally increase with added load.
It is debatable on how much fuel economy one would gain running a higher octane on a dual fuel engine, but I do know that it will increase its power output. This increase in performance will generally not be felt under normal driving conditions, but it would probably be noticeable under high load or high heat situations where you are constantly running in the engines power band.
For some, paying 5-10$ more every fill up may be worth the added 15-20 hp. For others it may not. I sure as heck would not spend that amount if I was doing it for fuel economy reasons unless It was proven that I can get a solid 2 mpg or better. That is pretty much around the break even point on a $.30 per gallon spread in fuel costs on a 16-18 mpg truck. On a 10 mpg truck that is towing, a 1 mpg increase would be about the break-even point at a $.30 per gallon higher fuel cost.
