S-80 fuel

IMHO, you should keep using the 93. Do you have the Sunoco brand? They have a

91 octane in our area (NH). The other option is to do a tank of 89 and a tank of 93. My son does that with his 850.

is it a 2.9 or a turbo?

For obvious practical reasons (marketing/advertising for a start) it's in the best interests of Volvo Corporate to provide cars that return the best possible mileage and performance numbers. Even when the gasoline recommended is somewhat more expensive, those interests are still being served.

The highest octane "premium" fuel most widely available in North America is (U.S. rating) 91. For them to say ". . . or higher if you can get it" adds unnecessary confusion, but should be obvious. For some years, Volvo Owner's Manuals have stated that 87 octane is the minimum acceptable. The cars will run on this fuel without damaging the engine, but both economy and performance suffer as the computer backs off ignition timing and advance to prevent knock.

Bottom Line: If Volvo could market quality vehicles that would run on kerosene (not a good example of l-o-w price anymore, just low performance) it would be in their best interests to do so. *So,* if a pricier fuel is recommended, it's because they know that, overall, their customers will be happier.

bob noble Reno, NV, USA

Thank you for your thoughtful response. I will continue to use 93 octane gas and see what happens. I know that as the car ages I should utilize higher octane fuel.

I think that 89 is the way to go***as long as you do not get 'knock' during normal operation--not during hard accel, but during normal use if no or very small knock...will be fine.

The car should have a knock sensor that will take care of it (though this necessarily compromises efficiency), but I can't agree that *any* amount of knock is fine. What you are hearing is the result of a shockwave being created in the combustion chamber.

Using a lower octane fuel than the engine is designed for can result in it not buring progressively as it should, but instead it responds to the pressure inside the combustion chamber by detonating with a flame travelling at supersonic speed. This not only stresses the engine components, but is inefficient. You may get away with it, but it is not fine - it can be very destructive.

For best efficiency, use a fuel with the octane rating the engine was designed for. If this is not available, use the next higher.

I wouldn't have thought that a good idea as the ECU 'learns' a set of operating parameters over time. If you keep changing the parameters by using different fuels it will never settle on an optimised calibration...... I would have thought it much better to stick with one or the other.

If you want a DIY solution to unobtainable octane ratings check this out.....

The non turbo has a knock sensor?

Virtually all modern electronic engine management units have knock sensors these days... It helps them to get optimum economy and performance from the engine.

Please answer the question, a general statement is not an answer. Does the non turbo 2.9 have a knock sensor?

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Yes, the 2.9 non-turbo does have a knock sensor fitted - as does just about any car that's fitted with an onboard computer. This allows the advance curve to run at the optimum for power and economy.

bob noble Reno, NV, USA