# Premium vs. regular gas **URL:** \ **Category:** Factual Questions\ **Created:** [June 20, 2008, 10:15pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629 "2008-06-20T22:15:51Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![snailboy](https://avatars.discourse-cdn.com/v4/letter/s/97f17d/32.png) [@snailboy](https://boards.straightdope.com/u/snailboy)\ **Post date:** [June 22, 2008, 8:53pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/21 "2008-06-22T20:53:50Z")
[QUOTE=Santo Rugger] Keep in mind that a higher octane does no good if your car isn’t designed for it. I’ve heard it can actually give -less- fuel economy if your compression isn’t high enough, because the fuel may not fully combust. I’m not sure if I trust that completely, but I do think the difference in a lot of cases is purely psychological. [/QUOTE] I don’t think the problem is that premium doesn’t fully combust, but that it combusts too slowly. ---
**Author:** ![Santo\_Rugger](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@Santo\_Rugger](https://boards.straightdope.com/u/Santo_Rugger)\ **Post date:** [June 22, 2008, 9:17pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/22 "2008-06-22T21:17:37Z")
[QUOTE=snailboy] I don’t think the problem is that premium doesn’t fully combust, but that it combusts too slowly. [/QUOTE] That makes a\* lot\* more sense, thanks. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [June 23, 2008, 11:46pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/23 "2008-06-23T23:46:12Z")
[QUOTE=samm] I am looking at buying a used Volvo (2002 s60) and some of the specs say it only takes premium gas. [/QUOTE] Echoing **Rick’s** questions, this doesn’t make sense. I suspect the word “specs” here is being used incorrectly. “Specs” are specifications, which are issued by the vehicle manufacturer. Typically there is one spec for gasoline octane requirement: the manufacturer is either going to specify premium gas, or not specify premium gas. It’s a flat either/or, the concept of “some” does not apply; and it’s the official word from the car’s maker. There should be no ambiguity. So some of _something_ may be saying it needs premium while the rest of said _something_ says it doesn’t, but that _something_ isn’t specs. ---
**Author:** ![Moriarty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/moriarty/32/49_2.png) [@Moriarty](https://boards.straightdope.com/u/Moriarty)\ **Post date:** [June 24, 2008, 1:42am UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/24 "2008-06-24T01:42:02Z")
[QUOTE=Gary T] “Specs” are specifications, which are issued by the vehicle manufacturer. Typically there is one spec for gasoline octane requirement: the manufacturer is either going to specify premium gas, or not specify premium gas. It’s a flat either/or, the concept of “some” does not apply; and it’s the official word from the car’s maker. There should be no ambiguity. [/QUOTE] I have the brochure for the new car I’m buying right here, and it says, under “specifications”, next to “Fuel”: _Unleaded 87 octane (premium recommended)._ How do you reconcile that ambiguity? ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [June 24, 2008, 1:45am UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/25 "2008-06-24T01:45:44Z")
No ambiguity there. The specification is for regular (87) however the car maker seems to believe that there will be a benefit for using premium. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [June 24, 2008, 6:03am UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/26 "2008-06-24T06:03:31Z")
My Thunderbird TurboCoupe took both and had a switch for it. It got better mileage with the premium but I never calculated which was cheaper. when I upped the boost to 18 lbs I always used premium. ---
**Author:** ![bienville](https://avatars.discourse-cdn.com/v4/letter/b/4bbf92/32.png) [@bienville](https://boards.straightdope.com/u/bienville)\ **Post date:** [June 24, 2008, 7:30am UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/27 "2008-06-24T07:30:37Z")
[QUOTE=Santo Rugger] in the US, an average of both the RON (research octane number) and MON (motor octane number) is cited on the pump. Since most countries use RON exclusively, your numbers would be the equivalent of about 87, 91, and 93. [/QUOTE] **Santo Rugger** (or anyone else who can answer), referring to my car’s manual to see what fuel was recommended I was confused to read: > [@](#): > > Unleaded Gasoline Octane Rating 87 (Research Octane Number 91) or higher From the information in your post, I now interpret this as “use 87 at your local gas station and you’re fine, my friend”. Do I interpret correctly??? (“local gas station” being in the U.S. in my case). ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [June 24, 2008, 12:16pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/28 "2008-06-24T12:16:16Z")
Yes you are correct 87 in the US is equal (more or less) to a RON of 91. ---
**Author:** ![Santo\_Rugger](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@Santo\_Rugger](https://boards.straightdope.com/u/Santo_Rugger)\ **Post date:** [June 24, 2008, 1:26pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/29 "2008-06-24T13:26:50Z")
Also note that the yellow sticker that shows the octane also says something to the effect of “Octane found using R + M / 2 method”. (They’re yellow in New Mexico, I don’t know if that’s a standard or not.) ---
**Author:** ![mazinger\_z](https://avatars.discourse-cdn.com/v4/letter/m/5f9b8f/32.png) [@mazinger\_z](https://boards.straightdope.com/u/mazinger_z)\ **Post date:** [June 24, 2008, 2:57pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/30 "2008-06-24T14:57:19Z")
If the S60 is a turbo charged engined, wouldn’t it require higher octane fuel? If so, would midgrade gas resolve any probable issues? ---
**Author:** ![samm](https://avatars.discourse-cdn.com/v4/letter/s/858c86/32.png) [@samm](https://boards.straightdope.com/u/samm)\ **Post date:** [June 24, 2008, 4:30pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/31 "2008-06-24T16:30:08Z")
Sorry it took me so long to get back to this thread! Rick, the one I am looking at is just the non-turbo FWD. The “specs” that I’m talking about are from here: [http://www.motortrend.com/cars/2006/volvo/s60/specifications/index.html](http://www.motortrend.com/cars/2006/volvo/s60/specifications/index.html) ---
**Author:** ![samm](https://avatars.discourse-cdn.com/v4/letter/s/858c86/32.png) [@samm](https://boards.straightdope.com/u/samm)\ **Post date:** [June 24, 2008, 4:37pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/32 "2008-06-24T16:37:58Z")
Sorry, it took over 5 minutes to actually post my message and then wouldn’t let me edit it. I posted the 2006 link, but the 2002 link says premium also: [http://www.motortrend.com/cars/2002/volvo/s60/specifications/index.html](http://www.motortrend.com/cars/2002/volvo/s60/specifications/index.html) ---
**Author:** ![control-z](https://avatars.discourse-cdn.com/v4/letter/c/eada6e/32.png) [@control-z](https://boards.straightdope.com/u/control-z)\ **Post date:** [June 24, 2008, 6:26pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/33 "2008-06-24T18:26:24Z")
I have a 2008 Mazdaspeed3 that requires 91 octane. However, we only have 87, 89, and 93 around here. The price difference is usually 10 cents between grades, but recently there is a 25 cent difference between 89 and 93 octane. So knowing that the engine could compensate for knocking and the most I was risking was some power and efficiency, I put a tank of Exxon 89 octane in. I got 342 miles on the tank of 12.5 gallons, which is 27MPG. Those numbers just as good as I got with 93 octane, and the car feels just as powerful. Acceleration still great. No knocking heard. I just put another tank of 89 octane in yesterday, I like to live on the wild side! ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [June 24, 2008, 6:54pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/34 "2008-06-24T18:54:40Z")
This octane issue is holding down some used car prices in particular. Some companies were heavy into turbo power in the past 3-7 years. You could save 5 grand on a car because its a manual tranny that takes premium. People don’t drive manuals and they don’t want premium. Math might be a friend here. Do the math. If a turbo powered car or car requiring premium is thousands less than similar models that don’t you might be better off saving 3-5k, because premium might cost less over the life of the car. If your annual fuel costs with regular is 4400 bucks, it might be 4700 with premium. Big deal. 300 bucks for premium/year? Some Volvos, Subarus, Audis and Saabs are WAY down in price vs. the competition (by anywhere from 2-6k) because of the need for premium in many of their models. Check the math before worrying, especially if you finance the car. Might be better to buy a $15k car that needs premium over a similar 18k car that doesn’t. ---
**Author:** ![Throatwarbler\_Mangrove](https://avatars.discourse-cdn.com/v4/letter/t/8c91f0/32.png) [@Throatwarbler\_Mangrove](https://boards.straightdope.com/u/Throatwarbler_Mangrove)\ **Post date:** [June 24, 2008, 7:17pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/35 "2008-06-24T19:17:51Z")
[QUOTE=control-z] I have a 2008 Mazdaspeed3 that requires 91 octane. However, we only have 87, 89, and 93 around here. The price difference is usually 10 cents between grades, but recently there is a 25 cent difference between 89 and 93 octane. So knowing that the engine could compensate for knocking and the most I was risking was some power and efficiency, I put a tank of Exxon 89 octane in. I got 342 miles on the tank of 12.5 gallons, which is 27MPG. Those numbers just as good as I got with 93 octane, and the car feels just as powerful. Acceleration still great. No knocking heard. I just put another tank of 89 octane in yesterday, I like to live on the wild side! [/QUOTE] You could fill up half with 89 and half with 93, then you end up with more or less 91. Also I believe the MS3 is rev limited(or is it boost…) in the lower gears, so you probably won’t get any knocking unless you’re bouncing off the redline in 4th gear and doing 250mph top speed runs? Direct injection helps too. ---
**Author:** ![control-z](https://avatars.discourse-cdn.com/v4/letter/c/eada6e/32.png) [@control-z](https://boards.straightdope.com/u/control-z)\ **Post date:** [June 24, 2008, 8:01pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/36 "2008-06-24T20:01:57Z")
[QUOTE=Throatwarbler Mangrove] You could fill up half with 89 and half with 93, then you end up with more or less 91. Also I believe the MS3 is rev limited(or is it boost…) in the lower gears, so you probably won’t get any knocking unless you’re bouncing off the redline in 4th gear and doing 250mph top speed runs? Direct injection helps too. [/QUOTE] Yeah I thought about the half and half thing, but it’s too much hassle. :o The MS3 makes maximum power about 1,000 RPM below redline, so there’s not much reason to go up there. That probably does help keep clear from knocking. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [June 24, 2008, 8:35pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/37 "2008-06-24T20:35:51Z")
[QUOTE=samm] Sorry it took me so long to get back to this thread! Rick, the one I am looking at is just the non-turbo FWD. The “specs” that I’m talking about are from here: > **[MotorTrend: New Cars - Car News and Expert Reviews](https://www.motortrend.com/)** > > Trust MotorTrend for the best car reviews, news, car rankings, and much more. With more than 70 years of experience, we're your home for everything automotive [/QUOTE] The links you posted are for turbo engines. The non-turbo engine for sure does NOT requuire premium. To the best of my knowledge the only turbo S60 that requires premium is the R line cars (2004-2006) The car you are considering buying is the same basic engine as my car, and mine is very happy on regular. Any other questons? ---
**Author:** ![samm](https://avatars.discourse-cdn.com/v4/letter/s/858c86/32.png) [@samm](https://boards.straightdope.com/u/samm)\ **Post date:** [June 24, 2008, 9:20pm UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/38 "2008-06-24T21:20:36Z")
Well… since you asked. How is this car on reliability? I love Volvos and my family has always had good luck with them. When I called my local Volvo mechanic to ask him what he thought about my considered purchase, he said the reliability went down when Ford took over and he would recommend a Toyota or a Honda for the fewest problems. But I really love the look of the S60! I didn’t want him to tell me that. I am just looking for someone to refute my trusted mechanic so I can feel good about ignoring his advice. 😉 ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [June 25, 2008, 1:45am UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/39 "2008-06-25T01:45:30Z")
[QUOTE=samm] When I called my local Volvo mechanic to ask him what he thought about my considered purchase, he said the reliability went down when Ford took over and he would recommend a Toyota or a Honda for the fewest problems. [/QUOTE] Volvo does their own thing. It’s ridiculous to think that their quality went down. The Ford M.O. is to use Vovlo’s technology (think the current Taurus and MKS) and and Mazda’s technology into their own business. Ford’s quality is regarded as par with Toyota and Honda for recent models (JD Power, etc.), and that has a lot to do with leveraging these assets. Heck, talk to a Jaguar or Landrover mechanic, and ask how their quality has gone _up_ since Ford purchased them (although they now belong to Tata). ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [June 25, 2008, 1:55am UTC](https://boards.straightdope.com/t/premium-vs-regular-gas/453629/40 "2008-06-25T01:55:11Z")
[QUOTE=samm] Well… since you asked. How is this car on reliability? I love Volvos and my family has always had good luck with them. When I called my local Volvo mechanic to ask him what he thought about my considered purchase, he said the reliability went down when Ford took over and he would recommend a Toyota or a Honda for the fewest problems. ) [/QUOTE] **Rick** sez they have good quality and so does my Mechanic. That being said, yes, Honda is tops, and has been so for a while. That doesn’t mean that Volvo is not first rate, just that Honda beats them. OTOH, Volvos are legendary for their safety. Toyota _used to be_ up there with Honda but it’s slipping a bit. Now Buick is likely #2. [Previous page](https://boards.straightdope.com/t/premium-vs-regular-gas/453629.md?page=1) [Next page](https://boards.straightdope.com/t/premium-vs-regular-gas/453629.md?page=3)