# Gas Ratings **URL:** \ **Category:** Factual Questions\ **Created:** [November 29, 2000, 12:27am UTC](https://boards.straightdope.com/t/gas-ratings/43117 "2000-11-29T00:27:15Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Trout](https://avatars.discourse-cdn.com/v4/letter/t/e9bcb4/32.png) [@Trout](https://boards.straightdope.com/u/Trout)\ **Post date:** [November 29, 2000, 12:27am UTC](https://boards.straightdope.com/t/gas-ratings/43117/1 "2000-11-29T00:27:15Z")
Does the octane of gas make any difference in the performance of your average vehicle (in my case a 4 cylinder Toyota)? I’ve tried 87 and 93 to see if there was any difference in mileage but didn’t find any. So is 93 rating just a rip off of the consumer by making them think that they are getting something better when it really is not? ---
**Author:** ![Caldazar](https://avatars.discourse-cdn.com/v4/letter/c/8e8cbc/32.png) [@Caldazar](https://boards.straightdope.com/u/Caldazar)\ **Post date:** [November 29, 2000, 12:47am UTC](https://boards.straightdope.com/t/gas-ratings/43117/2 "2000-11-29T00:47:35Z")
It really depends on the vehicle in question. Your best bet would be to check your owner’s manual to see what octane-rated gas you should use and then just stick with that. Some car engines, typically high performance ones, do require higher octane gasoline to prevent excessive engine knock. However, if you don’t experience engine knock with 87 octane gasoline under normal driving conditions, then I would think using the cheaper stuff would be alright. Again, though, you should check your manual just to be sure. Regarding fuel economy, my WAG is that the octane rating doesn’t significantly impact the number of miles you can drive on a gallon of gas. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [November 29, 2000, 1:11am UTC](https://boards.straightdope.com/t/gas-ratings/43117/3 "2000-11-29T01:11:21Z")
It seems to be a common misconception that a high octane rating should correspond to better gas mileage. This is not generally true. The octane rating is an anti-knock rating, and nothing else. You should use the higher octane only if your owner’s manual recommends it or if you have a problem with engine knocking. The additives they put in the gasoline to raise its octane rating usually has a _lower_ energy content per gallon than the gasoline itself. ---
**Author:** ![Homer](https://avatars.discourse-cdn.com/v4/letter/h/df788c/32.png) [@Homer](https://boards.straightdope.com/u/Homer)\ **Post date:** [November 29, 2000, 5:39am UTC](https://boards.straightdope.com/t/gas-ratings/43117/4 "2000-11-29T05:39:30Z")
Now, you can get higher gas mileage if your computer dials back your timing because of a low octane fuel. When you switch to higher octane you’ll get better mileage. My Chevy 3.1 gets about 3-5 mpg better w/89 than with 87. No gains are shown with 91. –Tim ---
**Author:** ![Feynn](https://avatars.discourse-cdn.com/v4/letter/f/ecb155/32.png) [@Feynn](https://boards.straightdope.com/u/Feynn)\ **Post date:** [November 29, 2000, 5:48am UTC](https://boards.straightdope.com/t/gas-ratings/43117/5 "2000-11-29T05:48:59Z")
I used to take a little drive (1000 km) over the Rockies a few times a year with my 4-Runner. My mileage was always better when I used premium fuel. The increase in mileage justified the extra cost at the pump. My Thunder-chicken likes premium fuel over regular. Now I remember the days of premium leaded fuel… mmmmmm!