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Discussion Starter · #1 ·
I called my dealership to talk about their new models. I was surprised to hear from the sales person that t5s (and B5s) are ok to go with 87 octane fuel. He told me he has a T5 and he never puts premium fuel in his car. I thought another sales person who doesn't know his stuff. I know the owner's manual says all volvo engine require high octane gas but than googled and found this:

- Volvo S90 Frequently Asked Questions | Crest Volvo Cars


Now my question is what is correct? Did I waste my money last two years by paying always for premium gas?
Some of the sources are saying you only need premium fuel for t6 or t8 and for t5 premium is nice to have. I thought T5 and T6 are the same engine with different software settings?
I know they are tons of threads about this topic but it seems there are contrary official information out there. Thoughts?
 

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When you open your gas filler door what does it say on there? I would suggest that.
 
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The T5 and T6 aren't the same engine -- they're variations of a common engine design. The T5 is the standard turbo model; the T6 has a lot of different parts to protect it against the extra power produced by its supercharger (which operates in addition to the turbo). I think premium fuel is nice peace-of-mind for a luxury car, and likely does mean that your Volvo will run a little better, but you could probably switch to 87 without ill effects. The only difference would be a smaller total at the pump.
 

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I called my dealership to talk about their new models. I was surprised to hear from the sales person that t5s (and B5s) are ok to go with 87 octane fuel. He told me he has a T5 and he never puts premium fuel in his car. I thought another sales person who doesn't know his stuff. I know the owner's manual says all volvo engine require high octane gas but than googled and found this:

- Volvo S90 Frequently Asked Questions | Crest Volvo Cars


Now my question is what is correct? Did I waste my money last two years by paying always for premium gas?
Some of the sources are saying you only need premium fuel for t6 or t8 and for t5 premium is nice to have. I thought T5 and T6 are the same engine with different software settings?
I know they are tons of threads about this topic but it seems there are contrary official information out there. Thoughts?
You can run 87, computer will dumb down to protect the motor to compensate for the lesser octane. (Provided that the systems components are functioning correctly) You will lose power when it’s warmer out and you are fully relying on the computer to make corrections to minimize knock. If you can afford it, run premium…..if not, run the cheap, I would recommend keeping my foot out of it when it’s hot out….say 70 degrees +. Especially on a stock FMIC.
 

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I just looked it up on Volvo website. T6 REQUIRES 91 minimum. T5 is OK at 87 but the engine will make more power with 91. How much more? It didn’t say. I have a T6 with polestar tune, I use 93, I drive 12k -15k miles per year. I also use 91 minimum in my 2017 S550 4.7 liter twin turbo. I have a Venza as well, 87 octane all the way as it is a NA engine. Detonation is the enemy of forced induction engines, hopefully your knock sensor will pull timing to prevent any misfire.
With my previous Audi A8 4.0 with a tune and downpipes 93 was a must. I always felt that at 560hp the engine had to be stressed under WOT!
 

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A sales person saying what will make you happy with your purchase? A dealer trying to get an edge in over their competition by being a bit shady with information? Say it ain't so! I've found the more direct I am about the topic the better folks take it. Talk up the engineered advantage of higher octane (and point out how little it actually costs more more per week), and it should be a non-issue to run the correct 91 or higher fuel.
 
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You can run 87, computer will dumb down to protect the motor to compensate for the lesser octane. (Provided that the systems components are functioning correctly) You will lose power when it’s warmer out and you are fully relying on the computer to make corrections to minimize knock. If you can afford it, run premium…..if not, run the cheap, I would recommend keeping my foot out of it when it’s hot out….say 70 degrees +. Especially on a stock FMIC.
I should also note that I run 98 octane along side 50/50 water meth.
 

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Definitive answer is YES, you can run 87, you can run 86.
But to me, the intelligent answer is read the manual, obey it, especially if you ever want to minimize warranty issues.
Yes the engine will retard timing to "minimize" knock, but it can only do that AFTER it hears it with the knock sensor, so basically, the engine has to already have knock in the first place before it adjusts.
If the cost is really that bad, or if 91 isn't commonly available and only 93 is, try mixing 93 and 89 or 93 and 87, just put in about 6 gallons of 93, and no more than 4-5 of the lower octane. You will still save a couple bucks each tank that way, and still have 91ish octane.
 
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Page 442 below - min. 91 required and 93 for optimum performance and fuel economy.

S90_OwnersManual_MY19_en-US_TP25977.pdf (harte-hanks.com)
+1
Another relevant bit in the same user guide (p. 443) is what is said regarding demanding driving (replicated below), which is similar to what user guides of latest ICE-engine vehicles generally say. Using lower octane than recommended will make the engine protect itself from knocking, but limits the engine's full potential (e.g. for towing or travelling up a mountain pass). Using higher octane doesn't always result in improvements if the ECU isn't programmed to take advantage of it. The s90 user guide that @Wayne T5 posted seem to indicate that the s90's ECU will take advantage of fuel at 93 octane (93 octane per AKI rating used in the US).

In demanding driving conditions, such as when towing a trailer or driving in hot weather or for prolonged periods at high altitudes, it may be a good idea to switch to a higher-octane fuel (AKI 91 or higher) or to switch to another brand of gasoline in order to fully utilize the vehicle's engine capacity and optimize traction
 

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Discussion Starter · #12 ·
Based on all what I see and hear, I think it makes sense continuing with premium but I still want to understand where this is following is coming from (see section about gas type), it is from an official Volvo dealer. It this would have been wrong, Volvo should/would have stopped it I guess??

 

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Based on all what I see and hear, I think it makes sense continuing with premium but I still want to understand where this is following is coming from (see section about gas type), it is from an official Volvo dealer. It this would have been wrong, Volvo should/would have stopped it I guess??

Their statement doesn't seem to contradict my interpretation (in post #11). They're just saying that a lower octane is OK for T5. I copy-paste the part from that dealer website that I believe you're referring to below:
Volvo recommends using premium unleaded 91 octane fuel or higher for optimum engine performance. However, a T5 engine can safely operate on 87 octane without impacting reliability. T6 and T8 variants are high-performance engines and require premium unleaded 91 octane fuel or higher.
While it is OK for T5, the dealer's statement doesn't say that it is not OK for T6 or T8, nor does it say that there will be no impact on performance. Reliability of modern ICE engines using lower octane is generally not a concern because the ECU can predict knock and makes the necessary adjustment (at the expense of reduced maximum power and/or torque).
 

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Ask the General Manager of the dealership if they will stand behind the claim that 87 is acceptable in the T5 if there are any long term issues that arise traced back to the 87.

I listen to the manufacturer when it comes to things like this. Some salesman know that premium fuel is a financial issue with some buyers so they downplay the requirement.
 
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T5 and T6 Volvo manuals state that they need premium fuel, no ifs ands or buts. My last SAAB 2,3 Aero turbo manual stated it will run of 87 or higher, but performance and mileage will be best with premium. We use 93 in our two V90 CCs; with my 9-5 I used 89 in the winter and 93 in the summer and never had any fuel-related issues.

Do you really think Volvo engineers specify premium because they want you to waste money? As Mr. Fantz pointed out, some dealers will tell you what you want to hear. I prefer to rely on the engineers.

If premium fuel is a "financial issue", do not buy a car that requires it. End of story.

p.s. Bring back the 3.0 straight six turbo that ran on regular, perhaps the nicest motor of any car I've owned. (y)
 

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I called my dealership to talk about their new models. I was surprised to hear from the sales person that t5s (and B5s) are ok to go with 87 octane fuel. He told me he has a T5 and he never puts premium fuel in his car. I thought another sales person who doesn't know his stuff. I know the owner's manual says all volvo engine require high octane gas but than googled and found this:

- Volvo S90 Frequently Asked Questions | Crest Volvo Cars


Now my question is what is correct? Did I waste my money last two years by paying always for premium gas?
Some of the sources are saying you only need premium fuel for t6 or t8 and for t5 premium is nice to have. I thought T5 and T6 are the same engine with different software settings?
I know they are tons of threads about this topic but it seems there are contrary official information out there. Thoughts?
Assuming your Volvo is rated for Premium gas (which I believe it is, but your user manual and fuel-cap door sticker will tell you for sure):
a lot of people say "the computer will adjust engine performance to accommodate to the lower octane". True, but the way it does it is by using the knock sensor. In other words, your engine starts knocking and then the ECU decreases performances (by delaying injection and/or ignition timing usually, maybe also lowering turbo boost if feasible). And knocking is bad for your engine. So I don't recommend it (although once in a blue moon is unlikely to hurt anything).
Also, engines are calibrated using the gas they're rated for. A back-up engine map is built for lower octane, but engineering will not spend as much time and efforts to develop it as they do for the optimal map. That can result in your engine not running as smoothly, but also some not-so-good things happening, such as burning oil (some VW turbocharged engines especially are very prone to that), building up soot, increased fuel economy, and also dirty emissions (the last point may not be people's primary concern), and also your automatic transmission holding gears for longer (since low RPM and high load is the scenario most prone to knocking).

At my local Costco, Premium is 17% more expensive than regular. Your fuel economy on regular may not increase by 17% but it will increase some (I don't have figures for this one). So your net gain will be lower than 17%.

Long story short, I'd avoid using regular gas in a premium-gas rated vehicle.

P.S.: I have a Master's degree in Automobile engineering, with a focus on powertrain development, and I spent a year working for a leader in engine development, doing engine calibration for OEMs (not for aftermarket/tuning; but for the "real" car and truck makers).
 

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Assuming your Volvo is rated for Premium gas (which I believe it is, but your user manual and fuel-cap door sticker will tell you for sure):
a lot of people say "the computer will adjust engine performance to accommodate to the lower octane". True, but the way it does it is by using the knock sensor. In other words, your engine starts knocking and then the ECU decreases performances (by delaying injection and/or ignition timing usually, maybe also lowering turbo boost if feasible). And knocking is bad for your engine. So I don't recommend it (although once in a blue moon is unlikely to hurt anything).
Also, engines are calibrated using the gas they're rated for. A back-up engine map is built for lower octane, but engineering will not spend as much time and efforts to develop it as they do for the optimal map. That can result in your engine not running as smoothly, but also some not-so-good things happening, such as burning oil (some VW turbocharged engines especially are very prone to that), building up soot, increased fuel economy, and also dirty emissions (the last point may not be people's primary concern), and also your automatic transmission holding gears for longer (since low RPM and high load is the scenario most prone to knocking).

At my local Costco, Premium is 17% more expensive than regular. Your fuel economy on regular may not increase by 17% but it will increase some (I don't have figures for this one). So your net gain will be lower than 17%.

Long story short, I'd avoid using regular gas in a premium-gas rated vehicle.

P.S.: I have a Master's degree in Automobile engineering, with a focus on powertrain development, and I spent a year working for a leader in engine development, doing engine calibration for OEMs (not for aftermarket/tuning; but for the "real" car and truck makers).
PPS.: Noted but not necessary.
 

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I called my dealership to talk about their new models. I was surprised to hear from the sales person that t5s (and B5s) are ok to go with 87 octane fuel. He told me he has a T5 and he never puts premium fuel in his car. I thought another sales person who doesn't know his stuff. I know the owner's manual says all volvo engine require high octane gas but than googled and found this:

- Volvo S90 Frequently Asked Questions | Crest Volvo Cars


Now my question is what is correct? Did I waste my money last two years by paying always for premium gas?
Some of the sources are saying you only need premium fuel for t6 or t8 and for t5 premium is nice to have. I thought T5 and T6 are the same engine with different software settings?
I know they are tons of threads about this topic but it seems there are contrary official information out there. Thoughts?
This is out of my 2018 V90 owners manual . . .

Octane rating
Volvo demands premium fuel (91 octane or higher) for all T5, T6 and T8 engines.

TOP TIER Detergent Gasoline
Volvo endorses the use of "TOP TIER Detergent Gasoline" where available to help maintain engine performance and reliability. TOP TIER Detergent Gasoline meets a new standard jointly established by leading automotive manufactures to meet the needs of today's advanced engines. Qualifying gasoline retailers (stations) will, in most cases, identify their gasoline as having met the "TOP TIER Detergent Gasoline" standards.


Thus, 91 octane or higher is a requirement and your dealership is incorrect (at least for my car). I do not know the year of your car or the motor that you have, but I would look at the label on the fuel filler door and the owners manual. Not worth risking your warranty if you are using the wrong fuel.

Also, as an aside, up and until the current motor family, Volvo had previously recommended premium fuel, but did not require it. That seemed to change with the SPA Volvos.
 
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