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Hi eveyone,

I just got a 2004 XC70 and am wondering which fuel grade I should use. Is 91 octane or higher required or recommended? If it's just recommended, will it be OK to use 87? If it doesn't affect the car much, that's what I want to use since the MPG is not that great. Does anyone have anything about this?

Sunny
 

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Try the lower grade fuel and see if it pings if it does then go up to middle grade and keep listening fr pinging.If it pings go higher.
Some cars run good on 87 and other need 91 or 93.
 

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Usually it is a sound like A muffled sound of change in a can.The noise will do it during acceleration if it is going to do it.
 

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I've read up on this topic in countless different sites and have finally come to the conclusion that the only definitive answer seems to be that no one has a definitive answer. Everyone just sort of skirts around the issue by saying premium is not necessary unless....
Even Volvo doesn't have a definitive answer since the manual recommends 91 but then says 87 is OK too. What's that supposed to mean? That's like saying you should drink imported bottled water at $2 a bottle, but your tap water is probably just as good.
I'm not really concerned about the performance issues, I just want to make sure I'm not causing any long term damage to the car by using 87. I've read the comments about the pingining test which seems sort of obvious. In any case Volvo's system is supposed to stop pininging regarless of what gas you're using. Does anyone have a technical answer as to what is really the difference between the grades? Not just that it burns slower, but how does the engine treat each grade and how does it run differently?
The only thing I've figured out for certain is that it will NOT improve your gas mileage regardless of what you read out there--not even the gas companies make this claim.
 

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Many engines (XC70 included) now include knock sensors which will adjust the ignition timing to the octane rating of the fuel you supply. That is why you can use 87 or 91 octane gasoline. The engine is designed to run optimally on 91 octane. You can provide 87 octane but the knock sensor will retard the timing to avoid the engine knock (or pinging) which does damage your engine. You don't have to worry about knocking because the ECU won't allow it. You do, however, pay a penalty in performance for using the lower octane fuel. Your acceleration may suffer a bit as a result.
 

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I don't mind the sacrifice in performance, but I do worry about the long term damage possibility. I know the engine can take care of the pinging and knocking even if I use 87 octane, but is there any actual damage being done to the engine in this process?
 

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But I was told that on turbo models, the lower octane can damage the turbo unit, thus causing much additional cost in replacing the unit. Am I being told the right info?

I have a 1998 XC70 AWD
 

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I have seen cars hit 200,000 miles on low grade gas with no problems.
 
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