# 7/11 now sells 5 grades of gas . . . do you ever use anything but "regular"? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [May 10, 2007, 11:20pm UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622 "2007-05-10T23:20:44Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [May 10, 2007, 11:20pm UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/1 "2007-05-10T23:20:44Z")
What’s the point of the other grades, anyway? Do they make your car run better? Get better mileage? What? ---
**Author:** ![MovieMogul](https://avatars.discourse-cdn.com/v4/letter/m/f08c70/32.png) [@MovieMogul](https://boards.straightdope.com/u/MovieMogul)\ **Post date:** [May 10, 2007, 11:23pm UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/2 "2007-05-10T23:23:02Z")
😕 What are the octanes? They’re usually two apart–did they add two more in between? Or are they 2 (and 4) higher than Premium? Or are they sub-Regular? I always buy Regular, and but wife’s Mini-Cooper needs Premium, so that’s what I buy if I’m filling her tank. ---
**Author:** ![thirdname](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@thirdname](https://boards.straightdope.com/u/thirdname)\ **Post date:** [May 10, 2007, 11:28pm UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/3 "2007-05-10T23:28:40Z")
I could understand 4: 87, 89, 91, and 93, but I’ve never heard of cars using a fifth grade. Maybe it’s not just gasoline, the fifth “grade” might be a gas-ethanol blend such as “E85”. PS edit: for those who don’t know already, you put in the grade that your car’s engine is designed for. There’s no benefit to higher octane unless the engine is designed for it, and lower octane can be harmful. ---
**Author:** ![MacTech](https://avatars.discourse-cdn.com/v4/letter/m/c0e974/32.png) [@MacTech](https://boards.straightdope.com/u/MacTech)\ **Post date:** [May 10, 2007, 11:51pm UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/4 "2007-05-10T23:51:30Z")
My Neon’s designed to run best on 87 Regular, so that’s what i feed it ---
**Author:** ![TheLoadedDog](https://avatars.discourse-cdn.com/v4/letter/t/35a633/32.png) [@TheLoadedDog](https://boards.straightdope.com/u/TheLoadedDog)\ **Post date:** [May 10, 2007, 11:52pm UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/5 "2007-05-10T23:52:47Z")
[QUOTE=riker1384] PS edit: for those who don’t know already, you put in the grade that your car’s engine is designed for. There’s no benefit to higher octane unless the engine is designed for it, and lower octane can be harmful. [/QUOTE] I keep hearing different things. Basically, I hear people say what you’ve said, but I am pretty sure it doesn’t always hold true. When I drove a '96 Corolla, it was designed for regular petrol, but when I put the better stuff in, it did seem to have a little more power (maybe I could have been imagining that), and it got better mileage (I wasn’t imagining _that_). When my stepfather bought a new 2000 model Corolla, the manual instructed him to use premium petrol, but the car dealer told him he didn’t need to at all, and to just use it every fourth or fifth tank if he was worried. That car is now seven years old, and runs like a charm on regular fuel. ---
**Author:** ![stretch](https://avatars.discourse-cdn.com/v4/letter/s/a6a055/32.png) [@stretch](https://boards.straightdope.com/u/stretch)\ **Post date:** [May 10, 2007, 11:54pm UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/6 "2007-05-10T23:54:55Z")
Regular for the 1997 Camry–it’s what she was raised on. Premium for the 1975 Triumph Spitfire–she was raised on higher octane gas. ---
**Author:** ![GorillaMan](https://avatars.discourse-cdn.com/v4/letter/g/50afbb/32.png) [@GorillaMan](https://boards.straightdope.com/u/GorillaMan)\ **Post date:** [May 10, 2007, 11:58pm UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/7 "2007-05-10T23:58:18Z")
There’s another recent thread on this - and one thing that transpired was that American Premium gas is similar to European regular. Which would explain a Mini Cooper handbook asking for Premium. ---
**Author:** ![TheLoadedDog](https://avatars.discourse-cdn.com/v4/letter/t/35a633/32.png) [@TheLoadedDog](https://boards.straightdope.com/u/TheLoadedDog)\ **Post date:** [May 11, 2007, 12:03am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/8 "2007-05-11T00:03:09Z")
[QUOTE=GorillaMan] There’s another recent thread on this - and one thing that transpired was that American Premium gas is similar to European regular. Which would explain a Mini Cooper handbook asking for Premium. [/QUOTE] Yes. Australian fuel is also gnat’s water. ---
**Author:** ![TastesLikeBurning](https://avatars.discourse-cdn.com/v4/letter/t/839c29/32.png) [@TastesLikeBurning](https://boards.straightdope.com/u/TastesLikeBurning)\ **Post date:** [May 11, 2007, 12:08am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/9 "2007-05-11T00:08:13Z")
[QUOTE=TheLoadedDog] Yes. Australian fuel is also gnat’s water. [/QUOTE] How is that? BP Ultimate is 98 Octane and so is Shell Ultimax (from memory), while our everyday standard ‘premium’ is 95. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [May 11, 2007, 12:14am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/10 "2007-05-11T00:14:56Z")
[QUOTE=TheLoadedDog] I keep hearing different things. Basically, I hear people say what you’ve said, but I am pretty sure it doesn’t always hold true. When I drove a '96 Corolla, it was designed for regular petrol, but when I put the better stuff in, it did seem to have a little more power (maybe I could have been imagining that), and it got better mileage (I wasn’t imagining _that_). [/QUOTE] There is no “extra power” to be had from high octane fuel. The energy content is actually slightly lower, though not significantly so, than lower grade fuel. I have no explanation for better mileage other than that detergents in the high grade fuel may have helped clean the injectors and valves, though I think that rationale is specious at best. You should, as **riker1384** says, put the fuel in the tank that the manual calls for. Yes, modern engine control systems will compensate for using a non-premium fuel in a high compression engine by reducing the compression, but that may not completely eliminate destructive detonation and is suboptimal. Higher octane fuel will not provide any benefit for an engine that runs at lower compression. Stranger ---
**Author:** ![TheLoadedDog](https://avatars.discourse-cdn.com/v4/letter/t/35a633/32.png) [@TheLoadedDog](https://boards.straightdope.com/u/TheLoadedDog)\ **Post date:** [May 11, 2007, 12:17am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/11 "2007-05-11T00:17:28Z")
[QUOTE=TastesLikeBurning] How is that? BP Ultimate is 98 Octane and so is Shell Ultimax (from memory), while our everyday standard ‘premium’ is 95. [/QUOTE] > **[Octane rating](https://en.wikipedia.org/wiki/Octane_rating)** > > An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compression the fuel can withstand before auto-igniting. The term refers to the equivalent ratio of a blend of iso-octane and heptane that produces the same knocking characteristics. Octane rating does not relate directly to the power output or the energy content of the fuel per unit mass or ... > [@](#): > > In many parts of Europe, 95 RON (90-91 AKI) is the minimum available, with 98 being premium. In other countries, like Italy, “regular” leaded gasoline, when still available, is sometimes as low as 85 RON (with unleaded still generally around 95 and premium around 98.) Looks like we’re both right. Depends where in Europe. So in some parts of Europe, our 95 ‘Premium’ is their 95 ’ Regular’, but Italy (the example they gave) is not ahead of Australia. ---
**Author:** ![Wee\_Bairn](https://avatars.discourse-cdn.com/v4/letter/w/90db22/32.png) [@Wee\_Bairn](https://boards.straightdope.com/u/Wee_Bairn)\ **Post date:** [May 11, 2007, 12:25am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/12 "2007-05-11T00:25:12Z")
I always thought really high end cars were the only ones that needed anything higher than regular, and that car manuals on regular cars that recommend premium were in collusion with the gas companies to encourage the purchase of more expensive gas. Anyway, that’s the excuse I give myself use for only using regular. ---
**Author:** ![GorillaMan](https://avatars.discourse-cdn.com/v4/letter/g/50afbb/32.png) [@GorillaMan](https://boards.straightdope.com/u/GorillaMan)\ **Post date:** [May 11, 2007, 12:31am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/13 "2007-05-11T00:31:53Z")
[QUOTE=TastesLikeBurning] How is that? [/QUOTE] Search for the previous thread (I can’t be arsed, I’m going to bed in a minute) - there’s different rating at work (and the Wikipedia article doesn’t cover it) ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [May 11, 2007, 12:37am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/14 "2007-05-11T00:37:18Z")
The octane rating has nothing at all to do with the “quality” of the gas. I really hate that they call higher octane gas “premium” gas. It’s not premium. It’s higher octane. It will compress further before spontaneously exploding than lower octane gas. That doesn’t make it better. You should use exactly the octane rating recommended in your car’s user manual, no more, no less. If you use a lower octane gas, you can get “pinging” or “knocking” in the engine, which is bad for the engine. The fancy computer controls and sensors of a modern car can compensate for knocking so that your engine probably won’t suffer any real damage, but the car won’t run as well. Using a higher octane gas than recommended usually is just pissing your money away, but in some cases it’s worse than that. Some cars actually get worse mileage on higher octane gas. Mrs Geek’s Camry says to use 89 octane gas. If you put 91 in it, it will run worse than it will on 89. “Premium” gas in this case is definitely NOT better gas. My Cadillac on the other hand says to use 89 or better. It gets better mileage on 91 octane than 89, but not enough to justify paying the cost difference. Generally speaking, the high compression engines found in performance cars are usually the only ones that require the higher octanes. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [May 11, 2007, 12:54am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/15 "2007-05-11T00:54:22Z")
I put regular gas in my BMW once out of carelessness. As soon as I drove off, I was highly worried that there was something seriously wrong with my car. There wasn’t exactly but it had noticeably less power and seemed to be screaming at me for what had happened. Only when I looked at the gas receipt did I know what was wrong and I was a little relieved. Since then, I have heard from other BMW owners that they really don’t like regular gas and the system will alter itself to compensate for it if it is ever filled with regular gas (it was fine after the next filling). ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [May 11, 2007, 2:03am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/16 "2007-05-11T02:03:39Z")
[QUOTE=Stranger On A Train] Yes, modern engine control systems will compensate for using a non-premium fuel in a high compression engine by reducing the compression, but that may not completely eliminate destructive detonation and is suboptimal. Higher octane fuel will not provide any benefit for an engine that runs at lower compression. (underlining mine) Stranger [/QUOTE] [nitpick] **Stranger** , you must be having a tough day. Unless the regular gas is going to bolt some new pistons in your engine, or change the head(s) on your engine, fuel will not change the compression ratio. Lower octane fuel will case the ignition spark to be retarded, lowering the peak cylinder pressures, and thus lowing the power output of the engine.[/nitpick] Many systems will, in the presence of severe spark, also inject additional fuel to quell the knock. This why using too low an octane fuel will cause the car to feel sluggish and have poor fuel mileage. It is possible that **TheLoadedDog** ’s Corolla had a slight detonation problem when running regular. This could be from several reason, such as carbon build up in the cylinders. If this occurred, then running a higher grade of fuel would have given better performance and fuel mileage. ---
**Author:** ![Fiddle\_Peghead](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiddle_peghead/32/3506_2.png) [@Fiddle\_Peghead](https://boards.straightdope.com/u/Fiddle_Peghead)\ **Post date:** [May 11, 2007, 2:53am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/17 "2007-05-11T02:53:48Z")
Buying premium is for suckers. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [May 11, 2007, 3:50am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/18 "2007-05-11T03:50:22Z")
[QUOTE=Fiddle Peghead] Buying premium is for suckers. [/QUOTE] Unless your car requires it. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [May 11, 2007, 10:54am UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/19 "2007-05-11T10:54:50Z")
Some cars may get a slight increase in performance with higher octane if their car is at the point that it is retarding ignition to prevent knocking. The middle of the 3 grades sort of solve this issue, if your car takes 87 but it’s a bit old it may need a bit more octane to prevent knocking. Making 93 available might solve this in cars that were designed for 91 but have aged past that as well. Lower then 87 can be used in higher altitudes so if you are in a mountainous area one grade may be below 87. ---
**Author:** ![gigi](https://avatars.discourse-cdn.com/v4/letter/g/a587f6/32.png) [@gigi](https://boards.straightdope.com/u/gigi)\ **Post date:** [May 11, 2007, 1:13pm UTC](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622/20 "2007-05-11T13:13:10Z")
I’ve only gotten something different from 87/regular when 87/regular was empty and I had no choice (like on the New Jersey Turnpike that time, and that may have been about the only time). [Next page](https://boards.straightdope.com/t/7-11-now-sells-5-grades-of-gas-do-you-ever-use-anything-but-regular/403622.md?page=2)