Most of the cars I own and drive have engines with compression ratios similar to the pressure of a firm handshake, or perhaps the effort needed to squish a ripe peach in your hand until it erupts its sweet, sticky juices, which then coat your fingers and one determined rivulet trails down the underside of your arm to your elbow, where it then drips, now free. This generally means that gasoline octane levels don’t matter that much to me. I just get the cheapest 87 octane juice.
But there are people with modern cars with genuinely impressive compression ratios that want nothing to do with knock or pre-ignition, so they need gasoline with higher octane, and so buy the rich, creamery fuel known as Premium, which has an octane rating of 91-94 and, I believe, smells like sex and leisure time.
That just leaves the middle grade, 89-90 octane “mid-grade” gas. Who buys this stuff? I mean, okay, there have been some cars that specify mid-range, 89 octane gas, but there weren’t that many. In fact, for cars currently being sold today, there are precisely nine cars that fit this requirement, and they are all either RAM 1500 trucks, Dodge Durangos, or one lone Jeep Grand Cherokee, all of which have the same Mopar 5.7-liter V8 engine. So, really, just one engine requires it.
Here’s another secret: there really isn’t any midrange gas. There used to be, but now it’s most often just a cocktail of 93 and 87, and in most cases is mixed in the pump, right there while you wait. I think they use bartender-trained elves chained up in the pump to do the mixing; I haven’t checked.
You can see how rapidly gasoline refiners have decreased how much midrange gas they produce here:
This cocktail of fancy and cheap gas is only purchased by about 7% of consumers, too.
So, who is buying it? And why are they buying it? Is it just based on the assumption that because it costs more, it must be a bit better? But not, like, rich-guy-premium better? Some of our writers mentioned in Slack that they had cars that knocked on 87 but were fine on 89, so perhaps that’s what the 7% is made up of? Car geeks with engines that have juuusssstttt too high compression for the cheap stuff, but don’t need the good stuff?
For most people, mid-range seems like a waste of money. But maybe there are some justifications for it? More mellow flavor? Deeper color? Who knows? If you have thoughts or justifications or just want to defend mid-range gasoline, now is your chance! Have at it!
Top graphic image: depositphotos.com
I used to run mid-grade in my Mini but usually due to cost concerns when times were tight.
It’s different here in Australia, obviously, we use RON instead so our low grade is 91 (straight petrol or E10), mid is 95 and premium is 98.
I frequently use 95 as some servos (service stations) only have 91 as an E10 fuel and I’m not running that through my metal tank, lines and carburetors in the utes. The utes can handle 91 with their 9:1 compression ratios.
The other two (Charger and WRX) have to run 98 octane, no exceptions or there will be holes in pistons.
the recommended fuel for a 2012-2015 bmw 328i and i’d assume cars with the same power train is 89. When I had one I’d just get mid grade and it was fine
My wife’s Honda Element specifies mid-grade, though it runs MUCH better on premium…like, a totally different car. It’s quite noticeable.
I cant remember the last time I bought anything other than 91 or higher. Even when I had the 3.6 VR6, it was all premium. Currently on 94 since its avail at Sunoco here in PHL now. I think I’d have to go back to the ’87 Jetta and the ’89 Golf to think of a time I used 89 octane which is going back to the mid 1990s. Didn’t want to be too freaking cheap, but I also had no money so 89 it is.
I have Jeep Gladiator Rubicon with the standard 3.6L V6 and a 6-speed manual transmission. I do a lot of what I call “2nd gear stops” because most of the time at busy intersections here in St. Louis, if you actually come to a complete stop, it really screws up the flow of traffic. On 87 octane (minimum octane per the owner’s manual), 2nd gear at “stop sign speed” really had the engine pinging for the first couple of seconds after my turn in the rotation. I used to have to rev match down to 1st which seemed a little rough on the transmission. Feeding it 89 completely removed the ping. To me, it’s worth the extra twenty cents per gallon.
One of the advantages of living in Canada is that Chevron sells ethanol free 94 octane gas. Since it takes me about a month to go through a tank of gas (I live on an island), I let my engine bath in a diet free or corn products. Is it expensive, yes. Is it worth it? Who knows. But I do notice I get better gas mileage.
I don’t think I’ve ever actually used mid grade gas. I’ve often wondered who does.
I usually fill up my wife’s Volvo. When she got it, she always wanted to make sure that the premium stuff went in. Our cheapness finally outlasted the fanciness of the car, and now she only demands mid-range.
Me, I never want a car that can’t handle the cheapest of the cheap…
My 5.7L Dodge claims to prefer 89 octane. I run 87 octane unless I’m doing heavy towing, then I go for 89. There is a noticeable difference when the vehicle is loaded.
I live at ~7000′, and regularly alternate between 85 and 87 in my Ram 1500 (as others have pointed out, the lower air density at elevation means you can get away with lower octane). However, if I know I’m going to be headed down the hill – either into the city (4600′) or all the way to Vegas (2500′), I’ll use either 87 or (if topping off) 91 to ensure that I’m closer to the recommended rating.
My car has a 11.5:1 compression and requires 91, which is the usual highest octane level in CA. I once put in Octane 100 or so (20 years ago, so I forget) when I was in Vegas for the drive home, and it ran extremely well. Recently went to a place locally that sells higher octane, but it comes in a 5-gallon can with no easy way to dispense without spilling it all over the side of my car.