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I was absent-minded at my last fill up. I put premium (93 octane) in my MY12 XC60 T6.

Since we bought the car -- about 7500 miles ago -- we've used only regular grade (87 octane).

Since the fill-up with the higher grade, I think the car runs smoother, better. But the difference is very subtle. This fill-up coincided with the dealer updating the transmission control module because the car was bogging under light acceleration when shifting from second to third gear. That may have also made the car feel like it's running better.

My question to forum readers: what are you using for gasoline and, if you've recently switched from one grade to another, have you noticed a pronounced difference?
 

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When I brought mine in for its 7500mi service interval, I complained about the acceleration causing the upshift too quickly resulting in the bogging down you are experiencing. The software update he applied fixed the problem for me with no change in my running 87 fuel. I tried several tanks of premium early on and found no significant difference so I stick with regular.
 

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Something makes me want to use 'premium', but I can't tell a difference in performance or mileage. In fact, we were over 23mpg on our last 1200 mile trip of mostly +-75mph highway driving(lightly loaded---the vehicle :) ---with two adults, one doggie and luggage)...ALL on 87 from either Exxon or Chevron. I've pretty much convinced myself that 87 is all I need unless we are in the mountains. Around here, it's about a 10% bump in price for 'premium'(.30-.35/gal) and I just don't see even a fraction of that difference in performance or mileage.

It's interesting that the manual states that it could take more than one tank for the vehicle to adjust to higher octanes. Over 54,000 miles, I haven't been able to discern any difference, BUT I'll admit I haven't used premium for 3-4 full fill-ups in succession.

I tend to want to use premium MORE in the C70, since it could use a little 'boost' in power ;) , but I can't say there's any difference in performance or mileage on that vehicle either. What I CAN say is the '11 C70 is getting solidly 10% LOWER mileage overall compared to our '08. Not sure what's up with that except for the tranny change.
 

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Discussion Starter · #4 · (Edited)
Something makes me want to use 'premium', but I can't tell a difference in performance or mileage. In fact, we were over 23mpg on our last 1200 mile trip of mostly +-75mph highway driving(lightly loaded---the vehicle :) ---with two adults, one doggie and luggage)...ALL on 87 from either Exxon or Chevron. I've pretty much convinced myself that 87 is all I need unless we are in the mountains. Around here, it's about a 10% bump in price for 'premium'(.30-.35/gal) and I just don't see even a fraction of that difference in performance or mileage.

It's interesting that the manual states that it could take more than one tank for the vehicle to adjust to higher octanes. Over 54,000 miles, I haven't been able to discern any difference, BUT I'll admit I haven't used premium for 3-4 full fill-ups in succession.

I tend to want to use premium MORE in the C70, since it could use a little 'boost' in power ;) , but I can't say there's any difference in performance or mileage on that vehicle either. What I CAN say is the '11 C70 is getting solidly 10% LOWER mileage overall compared to our '08. Not sure what's up with that except for the tranny change.
Thanks for the response.

But unless I understand the chemistry wrong, octane has nothing to do with mileage. It's a measure of the resistance of the gasoline to pre-ignition in the cylinder. Exploding at the wrong time causes the piston to "knock" and that can, over time, damage the piston, valves and rings.

Most engines that say you can use one grade as "recommended" but a lower grade with less available power implement a sensor which detects pre-ignition and changes the timing of the spark. (I don't know if the sensor advances or retards the spark.)

So, at least as far as I know, you would get precisely the same mileage with any acceptable grade for any given set of conditions. I don't know if altitude affects pre-ignition -- though it seems like it might -- but my question was really about whether people using premium "felt" any difference in power.

I can't.
 

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I reckon I would try to correlate a connection between 'power' and mileage regarding any performance differences in octanes. That is, a given amount of power is required to propel the vehicle...more power 'might' result in less fuel used at a given speed.

Honestly, I haven't heard an ignition ping from any of my vehicles since my '91 Miata. We didn't have our '95 VR6 Passat very long, but it may have pinged a time or two on lower octane fuel. Our '04 V70 'asked' for mid-grade, but I recall running a full tank of regular through it without incident.

A nice motorcycle fellow chastised me for putting 87 in the C70 one night. He looked to be about my age, meaning we started driving in the era of "Amoco/American 'white gas' "...perceived by many to be the purest form of petrol available at a gas station(1960s-'70s). Many felt it was truly a 'premium' gas, not only in octane but in quality. Old habits die hard, but I believe any top-tier petrol will be of high quality nowadays. I shoot for a bit more 'cleaning' in the form of extra Techron or Shell's nitrogen-based goo. I don't believe(as my motorcycle friend does) running 87 means lower quality and some sort of potential harm to the vehicle. It's still hard to shake the notion that a more expensive fuel is somehow 'better' for the vehicle. After all, we've been (mistakenly) told all our lives "You get what you pay for"...who the heck actually believes THAT? I'd say it's more accurate to believe "You DON'T get what you don't pay for but don't count on more than you DO pay for". Not quite as catchy, I'll admit. ;)
 

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Our XC60 T6 is right at 1year, with a whopping 19k miles. We've started using 93 octane just this summer, in response to a slight pinging experienced while accelerating up hills. We've had record breaking heat the past few weeks, so that could be contributing to the engine stress. After using the 93 octane the last few weeks, the pinging has gone away.

Earlier this year I did a quick MPG test. We started a drive from Atlanta to Orlando with about half a tank of gas (87 octane). I reset the MPG and MPH prior to leaving home. We drove about 200 miles on that half tank before needing to refuel. We averaged 25.5mpg on the interstate, at a 79mph avg. I filled up with 93 octane and reset the MPG and the MPH again. After another 200 miles on the same interstate, same speed, I averaged 26.5mpg. The environmental factors (temp, traffics, terrain, cruise) were exactly the same, yet the mpg was improved with 93. A total fluke? It could be, but it makes you wonder. Of course this wasn't enough evidence for me to switch to 93 exclusively, until the pinging started in the 100+ degree heat.

The best mpg we've ever gotten was driving state hwys/roads to 30A (gulf coast). We somehow averaged over 27.5 mpg while driving about 55-60mph average. Haven't been able to replicate this again, unfortunately.
 

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Unless you get the Polestar tune, I don't think premium is necessary. But if got Polestar tuned or the RD, Getting regular gas defeats the purpose of the extra power you paid for.
 

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Speaking from a Subaru background meaning a fussy engine with forced induction. Lower Octane will yield lower power the engine will pull some timing. But Optimum performance will be at what ever the car was tuned for IE. 91 or 93 octane. My STI has been tuned for 94 octane only.safest for my Subaru less chance for engine knock but mileage suffers do too high ethanol content in 94octane. In Canada Shell has 91 V power with NO ethanol. Somebody correct me but mileage improves Do to higher candle power more complete burn?
 

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Having just swapped our '10 T6 for the new RDX, it'll be interesting to follow the octane story on that one as well. Past Acuras were premium required, while our new n/a V6 is supposed to run on 87(with 'premium' performance from higher octanes). We'll see. So far, the RDX is getting a full 15% better gas mileage than the XC. That'll be a nice bonus if it holds(especially on 87).
 

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Having just swapped our '10 T6 for the new RDX, it'll be interesting to follow the octane story on that one as well. Past Acuras were premium required, while our new n/a V6 is supposed to run on 87(with 'premium' performance from higher octanes). We'll see. So far, the RDX is getting a full 15% better gas mileage than the XC. That'll be a nice bonus if it holds(especially on 87).

But. Is the power a lot less in RDX?
 

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But. Is the power a lot less in RDX?
273hp...so very close to our '10 T6 but less than the newer T6 and R-design. Haven't stood on it yet but it doesn't hurt that it's 500 lbs lighter, also. It's pretty quick for 'normal spirited' driving, so far.
 

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I've been lusting after the new RDX...it's a lot of features for the money. And it gets the same city mileage as me c30. But alas I'm trying to hold out for a while. Maybe look at xc40s when/if they finally get here
 

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My 2003 XC70 runs much better on premium than it does on regular.
 

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My 2003 XC70 runs much better on premium than it does on regular.
I recall our '04 V70 called for mid-grade and we usually mixed 89 and 93. I 'slipped up' on one trip and filled with 87 and couldn't tell a difference while driving +-75mph for the next 300 miles.
 

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Most engines that say you can use one grade as "recommended" but a lower grade with less available power implement a sensor which detects pre-ignition and changes the timing of the spark. (I don't know if the sensor advances or retards the spark.)
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For the most part, the owner's manuals in our newer Volvos will state that they are tuned for 91 octane fuel. This level of octane gives OPTIMUM performance. However, 87 is the minimum octane REQUIRED.

I use premium in my turbocharged Volvo. Its a personal choice...
 

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For the most part, the owner's manuals in our newer Volvos will state that they are tuned for 91 octane fuel. This level of octane gives OPTIMUM performance. However, 87 is the minimum octane REQUIRED.

I use premium in my turbocharged Volvo. Its a personal choice...
Also see if you can find 91 ethanol free your tank will go further:)
 

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The owners manual for all newer volvos states that you only get the advertised HP/TQ when using 91 octane or better. Yeah 87 may run fine but your 300HP T6 probably only gets like 260-270HP with 87. Granted, plenty of Volvo owners will never notice that loss...
 

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I have noticed a drastic difference in performance when filling with 91 or higher in every turbocharged Volvo I've ever driven. I don't feel it at first, but when I go to pass at highway speeds where I usually get a lot of pull as soon as I depress the pedal and suddenly the car feels like it's struggling - that's when I know.
 

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Also see if you can find 91 ethanol free your tank will go further:)
This is why I use 91 or 93 in the 3l T.
I don't believe E is good for these engines, and the mpg seems to be better on full gasoline.
 

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Also see if you can find 91 ethanol free your tank will go further:)
God knows I'd love to find ethanol free fuel other than Avgas.

I'm tired of all the crap ethanol does to my old cars and boats.
 
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