My volvo 94 940 requires high octane gas according to the manual but half the time I put in the cheapest stuff I can get. According to my research, a higher octane doesn't burn faster or is more powerful in any way. It just takes a little more power to ignite. Different octanes determine timing of the burn etc. Is this true? In my experience, higher octanes give my old volvo a significant power boost especially at highway speeds. High octane costs approx 7% more than the cheap stuff. Would any of you know if higher octane would improve mileage at all? even a 4% boost would give me the excuse to buy the more expensive gas every time. It would be interesting experiment if no one knows the answer.

 

I have dwelt on this same subject and arrived at the conclusion that: premium fuel does give better fuel economy and perhaps better performance but that's hard to measure. Also, this depends on the car. Still, I put regular in my 1994 940 as long as it doesn't ping.

 

Mine used to ping bad when going up hills. The solution was to pop the cam cover off and tighten everything down. Almost all of the ping is gone.

 

IMO, Premium gas does give some increase in gas mileage. I have experienced this in my 1999 s70 awd. I always used Regular and got decent gas mileage out of it.

However I switched over to Premium gas and it was I don't know that much better then using Regular. However the price of Premium is sometimes not in my range of what I want to pay.

Then it hit me. I might be spending anywhere from $45-$50 for regular everytime I fill up the tank. Well at $2.65 a gallon for Regular that is what I paid last. The next up was $2.75 and then $2.85. I thought to myself it is only about $2.00-$3.00 for using the high grade Premium gas then it is to use Regular gas. So I try to put Premium in my tank when I can. I can also tell the car likes Premium better then Regular.

 

The volvo engine computer will advance the engine until the knock sensor detects ping then back off 5 degrees. Then it comes back and goes up more slowly until ping and backs off 2. So you will get slightly more miles per gallon with premium because the computer can advance the timing slightly more..... I run regular cause i am too cheap... but that is how it works.. It will advance the timing as much as it can for the gas youre using.