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Is higher octane gas fuel-ish for my crossover?

Richard Buchan/The Canadian Press

I just bought a 2011 CR-V. The manual says that using 87 octane gasoline is fine, but I would like to know if there is an advantage to using a higher-octane gasoline. – Joseph

The only possible benefit would be the higher quantity of cleaners usually included in higher-grade fuels.

The Engine Control Module or Unit (ECM or ECU) in your car is not designed to take advantage of higher octane fuel. These units, using information from a wide variety of sources and sensors, determine the amount of fuel to inject into an individual cylinder, and the point during the operating cycle at which the spark plug fires. When the engine is cold, it sends a richer mixture – which used to be done through a device called a choke.

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In some higher-performance engines where premium fuel is recommended or required, the engine control system is programmed to retard the timing if regular or lower-octane fuel is encountered.

This is done to prevent what is called knocking, which can cause serious engine damage. Knocking occurs when the fuel air mixture detonates or ignites prematurely because of the pressure in the cylinder, not the spark from a spark plug. The common cause is a fuel/air mixture that is too lean – i.e., not enough fuel – or in this case a lower-quality fuel. When the ECU senses this occurring, it retards the timing or point at which the spark plug fires until slightly later in the compression cycle.

Since knocking commonly occurs at lower engine revolutions, the ECU might also tell the transmission to shift to a lower gear to increase engine revs. But, the reverse is not the case, the control system in your car will not advance the timing and produce more power when it senses higher octane fuel. Save your money.

Manual shifter

I have a problem with the manual transmission on my 2010 Ford Fusion. When it is minus-15 Celsius or lower, the manual shifter knob does not pop up after using reverse gear. As a result, it is possible to shift into reverse by accident . After about 20 minutes of driving, this problem disappears. Is this a problem common to the manual transmission Fusion? Are there any recall bulletins related to this problem as it could create a dangerous situation. – Paul

I can't find any bulletins on this issue so have to assume it is unique or at least fairly rare.

It sounds like a return spring is binding or there is a lubrication issue. You don't say whether you can pull the lever up manually or have to wait for things to warm up sufficiently to work in a normal manner. I'd suggest getting it to a shop where a qualified technician can get it up on a hoist and at least determine if it is the linkage or something inside the transmission.

If the former, it should be relatively easy to tackle as a visual inspection while operating the shift lever should identify the source and likely cure. It could be debris caught in the tight confines where the linkage operates, a broken spring or a lack of lubrication. It is also possible the linkage became bent slightly at some point and is rubbing against something just enough that low temperatures are changing the operating environment.

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