Am I wasting money on premium fuel?

AP · Post by AP » 09 May 2007, 11:16

I have a 2000 S70GLT with around 135K miles on it. I have always used Premium fuel (91 ocatane) . The drivers manual says:

"Volvo engines are designed for optimum performance on unleaded Premium gasoline with an octane rating. AKI of 91, or above. The minimum octane requirement is AKI 87 (RON 91.)"

I'm from Sweden where the lowest octane you can get is 95, and when I fist came over here and saw you can purchase 87 octane, I thought it would cause pre ignition and wear down a European engine fast. But with gas prices hitting close to $4.00 for premium I'm wondering if I'm just wasting money putting premium gas in my Volvo?

Anyone have any good thoughts on this?

Black850 · Post by **Black850** » 09 May 2007, 11:29

Alright, another fuel thread! Just messing. One, I believe europe and america use different rating systems for their octane, so comparing the 2 grades is not valid.

Second, the timing will adjust to the lower fuel grade. So the car will run fine, just not at its max performance level.

Third, when you take a look at the difference, it's not THAT much. The overall cost is a hit with whatever grade. However, the difference between the lowest and highest grades are 20 cents. Take 20 cents times 18 gallons. That's about $3.50. Generally speaking, you're not filling up a bone dry tank.

So weigh your options, and ultimately do what's best for your circumstances.

volvrow · Post by **volvrow** » 09 May 2007, 13:28

Based off of my experiences you get somewhat better fuel economy with the premium fuel- so there really is minimal cost savings to buying "regular". I tested it a couple times and it costed me only a few extra dollars for premium. Given that, the premium octane is better for your engine and burns cleaner, so I would go with premium even though there is sticker shock at the pump right now.
Not sure if others would disagree, b/c it is an interesting debate...maybe they should perform a test on the show Mythbusters!

volvrow

zenmervolt · Post by **zenmervolt** » 09 May 2007, 16:36

AP wrote:I have a 2000 S70GLT with around 135K miles on it. I have always used Premium fuel (91 ocatane) . The drivers manual says:

"Volvo engines are designed for optimum performance on unleaded Premium gasoline with an octane rating. AKI of 91, or above. The minimum octane requirement is AKI 87 (RON 91.)"

I'm from Sweden where the lowest octane you can get is 95, and when I fist came over here and saw you can purchase 87 octane, I thought it would cause pre ignition and wear down a European engine fast. But with gas prices hitting close to $4.00 for premium I'm wondering if I'm just wasting money putting premium gas in my Volvo?

Anyone have any good thoughts on this?

Europe and the US measure octane differently. US "87" octane is equivalent to 91 or 92 Octane rating in Europe.

US 92 Octane (the "premium" where I live, some places have 91 or 93) and US 92 Octane is roughly equivalent to 96 or 97 octane in Europe.

If the engine is designed such that it can take advantage of the higher octane, then it will run best with the higher-octane fuel. When lower octane fuel is used, the engine compensate by retarding the timing and cutting back on boost from the turbo. Since the engine effectively "de-tunes" itself when low-octane fuel is used, it is slightly less efficient when using regular.

If the engine is designed to run on 87 and the manual says only to run 87, running premium is actually worse for the engine. Higher-octane fuels have a slower-moving flame front and will leave carbon deposits in engines not designed for those fuels. In these cases, the engine will get worse mileage with premium.

The "rules" are thus:

1) If the manual says the engine only needs 87, run 87 in it and never worry about premium.
2) If the manual says the engine needs premium, run premium.
3) If the manual says that the engine "delivers maximum performance" on premium but only requires regular, the engine employs a knock-sensor and other technology to allow it to safely run on regular fuel without damage, albeit also with a reduced power output.

You can run your car on regular without worrying about causing any damage at all. However, you will be sacrificing some power to do so.

Crankin · Post by **Crankin** » 09 May 2007, 20:41

I am just wondering if maybe you could run midgrade gas and get the best of both worlds?? I think it is 5cents more than 89 octane and 5cents less than priemium per litre. Would the "middle of the road" not be okay? I am asking because I have just put in new O2 sensors and would like them to last for ever!!!!!!

zenmervolt · Post by **zenmervolt** » 09 May 2007, 21:24

Crankin wrote:I am just wondering if maybe you could run midgrade gas and get the best of both worlds?? I think it is 5cents more than 89 octane and 5cents less than priemium per litre. Would the "middle of the road" not be okay? I am asking because I have just put in new O2 sensors and would like them to last for ever!!!!!!

As above. Same rules.

- If your engine only requires regular and doesn't say anything about premium, then running midgrade is also a waste.
- If your engine requires premium, then don't run midgrade.
- If your engine says that it can run on regular but that premium will "provide best performance" or is "recommended" or any similar phrasing, then you can run mid-grade but will suffer some power and efficiency loss, but will not damage your engine.

As for O2 sensors, they will never last forever. 100,000 miles is pretty much the maximum life for modern O2 sensors. Running rich can damage an O2 sensor and so can using leaded fuel, but low-octane cannot.

turbotim2 · Post by **turbotim2** » 10 May 2007, 06:32

Run regular! The other fuels will give you no added benefit. These are family sedans not sports cars! Save the money in fuel for repair parts or beer.

zenmervolt · Post by **zenmervolt** » 10 May 2007, 09:09

turbotim2 wrote:Run regular! The other fuels will give you no added benefit. These are family sedans not sports cars! Save the money in fuel for repair parts or beer.

Wrong.

The manual would not say that the engine is designed for 91 and above if it couldn't take advantage of the higher-octane fuel. You can run 87 without damaging the engine, but it will make less power because the ECU will be retarding timing (and, in turbo vehicles, also reducing boost pressure) to prevent detonation (aka spark knock).

If you don't want the extra power, that's fine, you won't hurt the engine by running regular, but you'll be down on power.

turbotim2 · Post by **turbotim2** » 10 May 2007, 09:14

What part of my statement was wrong, you effectively agreed with me. The benefit of 0.4 hp increase is hardly worth a mention or the additional cost. Come on people look at what you are talking about. If these were 600 hp engines used for racing where every bit counts then we have an argument.

zenmervolt · Post by **zenmervolt** » 10 May 2007, 09:19

turbotim2 wrote:What part of my statement was wrong, you effectively agreed with me. The benefit of 0.4 hp increase is hardly worth a mention or the additional cost. Come on people look at what you are talking about. If these were 600 hp engines used for racing where every bit counts then we have an argument.

The additional cost on a tank of gasoline is around $3.20 assuming the standard $0.20/gallon difference in price and a 16 gallon fill-up. If you're that hard up for cash, you should probably dumpt the Volvo and buy a Tercel or something that gets double the mileage.

And the power difference is on the order of 15-20 hp for non-turbo vehicles and can be 30-50 hp on the turbocharged models if the ECU starts cutting boost. I don't know where you pulled the "0.4 hp" number from.