Quote:
Originally Posted by Texas Coyote
The manual says that 87 octane is the lowest that can be used in the Fit.... The ECU will retard the timing to not have the engine ping with lower octane fuel and allow more advance with premium and improve your gas mileage and performance as well as contributing to less carbon deposites in the combustion chamber..... The 2007 model has a 10.4 to 1 compression ratio which would have called for leaded premium (ETHYL) gasoline back before unleaded fuel and ECUs.....
|
Modern engines and ECU's will not advance ignition timing given a higher octane fuel than it was designed for, it will only retard it on the chance that something lower than it was designed for is put in. Nor is static compression ratio a good gauge for what octane will work best in the car . . . you need to calculate in many other factors, such as dynamic compression ratio, piston and combustion chamber design, engine operating temperatures, typical load, etc. etc. 50 years ago a 10.4:1 compression ratio running on 87 octane would have been near impossible, and 30 years ago it would have been remarkable . . . But these days, it's fairly commonplace.
Quote:
Originally Posted by Texas Coyote
If you are now using regular,smell the oil dip stick and you will find that it smells like gasoline., that is because when the timing is retarded the fuel doesn't completely burn and gets into the oil . . .
|
Not exactly an accurate test of whether your timing has been retarded. I use regular exclusively on this car, and my last oil analysis showed a fuel percentage of only .8%, which is quite low, especially considering I took the sample from a cold engine.
An even more accurate (and immediate) test to see whether the 87 octane is holding back performance would be an OBD2 scanner. Just log out timing advance using the 2 different octanes, and you've got your answer.
You can find examples where the difference between premium and regular gas has been dyno tested on cars rated for 87 . . . in every one I've seen, the higher octane fuel does no better - and usually does worse. There's nothing in the Fit's design that makes me think it'd be any different. :shrug: