Premium fuel ?

[atxf4i]

If I use less then premium, my CEL comes on with the code for the Front Knock Sensor. It turns off with higher octane gas.

[lesII]

from LesII

My experience for what it is worth is that you will see reduced "off the line" and full throttle power loss using 87 octane gasoline in any 2.4 engine, however my gas mileage is exactly the same, after giving the computer a few tanks to catch up
my 1994 2.4 850 with 181,000 miles get 21 city 26 highway and my 1999 v70 2.4T with 178,000 miles gets--21 city 26.5 highway on regular
I imagine a t-5 or higher would require premium
thanx for reading

[instarx]

I have used 87 in my car since I got it four years ago, but last month for some reason I decided to put 91 octane in it. I was amazed - not at the power output because I don't drive aggressively enough to notice - but at the immediate effect on around-town MPG. My MPG readout went from 17.5 average to 20 average almost immediately. This improvement was verified at my next fill-up when I did the actual math (I keep meticulous records). Yes, I know power, MPG and acceleration are all inter-related, but all things being equal the MPGs went way up for me from the change in octane.

I calculated the extra miles/tank vs the extra cost of 91 ocatane and they almost exactly balanced out. The 91 was very slightly more expensive to run. I did not notice any MPG improvement over normal on a recent long distance trip though - the improvement seems confined to around-town.

So I now use 91 or 93 octane all the time. If its better for the car then that is a nice bonus.

[jimmy57]

I have a Volvo Scan Tool. It has full real time display of info from ECM on 960's, most 850's, and all 98 s/v/c 70's
I have watched the knock sensor levels on both knock sensors with the three grades in winter and summer. In winter 87 will give me 3's with heavy acceleration. When temp gets to mid 80's the number will easily get to 5. in 100+ summer temps mid grade gives me 3's and premium gives me 2's. The knock retard ignition timing level is maybe 1 degree different between 2 and 3. When it gets to 4 the timing is retarded 2.2 more degrees and 5 is a further 3 degrees. My point is 3 is the unnoticeable likely no MPG penalty level. I use mid-grade and the car runs very spiritedly even when it is 110 out.
At lower throttle levels the knock sensor levels and timing retard levels are less.
We all drive differently so there is not an apples to apples comparison that can be made but in my days of having multiple different Volvo company cars I never used premium (OK, prem in the R when it was HOT) and for the non-turbos I would not go above regular except when it was mid 90's or above.
The only fuel level problem that ever cropped up was low octane and pulling I70 grades from just west of Denver on up. Some cars will get a lot higher on temp gauge on low octane as the knock retard level will get high enough to make coolant temps climb. Low octane in Denver is 85 with the altitude reformulation done to fuels (hmmm, they don't drop price when the comparable octane level is lowered do they?).

Injector and port deposit levels have not been an issue with any of the octane levels for years now, probably gone since the mid 90's. The issues with engine/component deposits with lower grade and certain brands pushed the fuel industry to go with a reasonable detergent level in all grades when a few car makers started recommending specific brand fuels.

[KlubMarcus]

For turbo's minimum is mid-grade. Use the GasBuddy app to find good deals for premium around town.

[rmmagow]

My 98 AWD low pressure turbo runs very well on 89, not so well on 87 and no real change at 94. Mileage on 89 is about 24.8, 87 was somewhat lower at 22.5, 94 was still at 24.8. Each test was run with 5 tanks of each type of fuel and using the on-board computer. My drive is 100 miles a day commute + various types of weekend driving. Winter numbers in all categories dropped some but not much. I run either Sunoco, near home or no-name from near work.

[ChiNorm]

Klaus on the Brickboard forum will show you pictures of motors damaged by using regular in a T5.

[jimmy57]

My XC70 has a 20,000 mile B524t3 with a higher base setting on wastegate but no other mods.