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
In Europe (at least in Germany and a few other countries) there are usually only two grades of petrol available: “Super” (95 RON) and “Super plus” (98 RON). (RON or Resarch Octane Numbers are always a bit higher than the AKI numbers used in North America.)
We used to have “Normal” petrol (91 RON) as well but it was phased out quite a long time ago, as it wasn’t cheaper than “Super” anymore, and there was just no reason to keep it available.
That is how it works in Portugal too, could be a EU thing. But here in Portugal we always have two options for each; you have ”regular” and “premium” versions of both 95 and 98 – regular versions are just normal gasoline, the same stuff in every pump. Premium is supposed to have additives exclusive to each brand, marketed as allowing for better gas mileage, less harmful emissions, and helping with engine longevity.
Never tried premium gas, and also never tried 98, but I’m curious about the difference that 98 would make for my daily driver’s engine (Cléon-Fonte C1E), since it was designed in the late 50s by Renault with some pre-war tech and last updated in 1985. My 91 Renault 4 has this final update, detuned from 44hp to 34hp for the final years of production; this was achieved mostly by going with a 28mm Zenith carb instead of the 32mm Solex. As the engine tends to run very under stressed the vast majority of time (you really need to get in the highway and push it hard for the engine to start complaining), it never really made much sense to me, pumping 98 instead of 95 – which this final version of the C1E engine is supposed to handle just fine anyway. But some owners swear by 98 octane gas, saying the engine runs much smoother and that the improvement in gas mileage offsets the price at the pump. I guess I should do a few tanks of 98 to see what the fuss is all about.
I glossed over the fact that some petrol station chains have some extra premium petrol (like Shell V-Power or Aral Ultimate), but that usually replaces Super Plus. They won’t have both, normally.
There are also two versions of “Super”: E10 and E5, depending in the amount of ethanol mixed in, but both versions have 95 RON (or ROZ, as we say in Germany; Z for Zahl replaces N for Number).
To be fair I’m not 100% sure all pumps have all 4 choices, and if this can change from station to station, even for the same brand. I know some Repsol, BP and Galp (formerly state-owned oil refiner and distributor) stations that all have the four choices, but we do have “discount” gas chains (normally operated by supermarkets) and I’m not at all sure those have all options; they may not offer premium choices entirely, as their entire point is that gas is cheaper there.
Forgot to mention, but I always love your contributions to any discussion on this site. You never fail to bring in interesting information; I’d never realised octane measurement differed between the USA and EU, always thought the US just had very low octane gas to make sure engines don’t last that long haha.
Does anyone use nitropropane?
Other additives?
Race fuel mixed with regular?
My first Dodge Challenger was a 2008 R/T. I’m pretty sure it asked for 89 octane, which I thought was odd as heck.
For some reason I think the HEMI in all applications recommended 89.
Only the 5.7 and HD Ram’s 392. Everything else is 91.
I buy midgrade. My v6 Audi required 91, and my i6 BMW also requires 91, but I can find it nowhere other than when we visit in-laws in Wawa-land. 89 it is most of the time. Neither engine was/is turbocharged though. My turbo Audi and, hysterically, turbo HHR SS received 93 when I had them. A single shop where I live has ethanol-free 90 octane, and I get it if i’m on that side of the street. But it costs the same, or more, than 93 octane across the street, so I haven’t patronized it.
Back in the late 90s I put mid-grade in my parents 1988 Oldsmobile Custom Cruiser to stop it from dieseling when I shut it off. Worked great.
Oh wow, just learned about this dieseling phenomenon. I drive a carbureted, somewhat high-mileage engine, but I don’t think this ever occurred to me, was it maybe more prevalent in larger more powerful engines? Mine’s a 34hp, 1.1L four-barrel.
I buy mid-grade.
Here in CO and similarly altitudinous states, mid-grade is 87, the cheapest is 85.
My Ford Maverick requires 87 so I have to buy mid-grade..
previous Ford got 85 all the time, with no ill effects noticed over a decade and 100 000 miles..
also used to put mid-grade into the MDX that required 91, it also ran fine for decades on mid-grade with an occasional treat of premium gas.
The ’83 Monte Carlo SS calls for mid-grade, so that’s what it gets
“knocked on 87 but were fine on 89”
Oh! There’s your obvious answer…
Doc Brown buys mid-grade so the DeLorean can run 88 octane at 88MPH!!! Must be a magic octane # + magic speed…you finally figured out the secret to time travel…
Congratulations!
Down Under the minimum is 91 octane, then there’s the 10% ethanol blend, 95 and then premium 98. I haven’t seen anything under 91 for decades. The majority of cars in Australia have been Australian, Japanese, Korean or European, however there has been a significant increase in Chinese vehicles over the past few years. A lot of these different vehicles probably have higher compression and therefore require a higher octane.
Different countries use different calculation approaches. The equivalent gasoline will be 4-6 units lower in the US due to methodology. https://en.m.wikipedia.org/wiki/Octane_rating
In my area a few gas stations sell ethanol free gas that I typically run in my carbureted motorcycle and small power equipment and for some reason the ethanol free gas is usually mid grade so that’s the only reason I buy it.
Several of my older car engines have been rebuilt. Once you shave the heads a few times the compression goes up requiring a bit more octane. 89 is often a good choice.
My dad uses mid grade anytime he fills up the Lexus CT we have. It doesn’t need premium, but we aren’t comfortable with regular.
You’re flushing money down the drain. It’s a gussied up Prius and will run fine with 87 octane gas. I’ve been running E15 88 octane in my Ford hybrids for years. No mileage penalty, and it’s usually 30 cents cheaper per gallon than E10 regular. Had 274k miles with no engine problems (it was totaled in an accident a couple of months ago.) Got an Escape PHEV, now I’m getting 50 mpg and paying 2.21 a gallon for gas.
5600’ elevation Gas here comes in 85 octane regular, 87 mid grade, 91 premium. 17 RDX, owners manual and gas door says use premium. No recognition of altitude differences with octane. Sales people said midgrade is ok. I tried a few tanks of mid grade and tried a few premium tanks when I got the car. I use mid grade. I’ll go that far. Fuck them before I’ll pay for premium and car seems to run the same on mid. I’m disappointed with Acura that the car gets barely 20 mpg and needs premium gas. When I asked the Acura service people about the octane at altitude topic they were very noncommittal.
our 2006 MDX in Denver has run from 2012 until now on mid-grade 87 with no problems, still going strong at 190 000..
it is a luxury car, with a high performance engine, so not unexpected that it needs premium.
I’d put in 91 for long mountain/fast trips with heavy loads, otherwise all 87.
My 2011 Acura TSX Wagon recommends 91 octane. It says 87 can be used temporarily but long term use will cause knocking and engine damage. So I use 89 octane.
However, I generally buy fuel at Costco – which doesn’t have those fancy pumps that mix up some 89 octane on the fly. So I have to mix it myself with two transactions.
In the Midwest, there is a subsidized E15 blend that comes in at 89 octane, and so there are many places where that is the cheapest grade.
I just gassed up with E15 and it is consistently 30 cents cheaper than all the other blends.
There may only be 9 brand new cars that take 89, but historically it used to be more and your graphic showcases this trend. There are still plenty of older vehicles on the road that recommend 89.
89/90 used to be what stations noted in the Midwest for 10% ethanol blend in the aughts and teens, but now it seems they are blended down to 87 as the stations will have 87, 87(ethanol), and 91+ premium. Not every station is a two tank and quite a few still have a 3 tank system for guzzoline.
Still many in Minnesota that are E15 89 octane, and that is the cheapest grade available. Cheaper than E10 89 or whatever ethanol ratio is in 91
I’m at fault for not putting IA/NE in regards to my 87 ethanol (probably 15%). There are a lot of comments about the Midwest, but it’s very different state to state for what is offered.
Yes, often by 20-30 cents a gallon cheaper.
There were some vtecs in the early 00s that wanted it. I suspect they ran ok on 87 probably just detuned a bit. But knew several people that had them and they always mid grade or premium.
DOHC VTECs of the ’90s definitely needed premium, but the SOHC ones were fine on regular.
My dad did for ages, no idea why.
Some people around here go for 91 without requiring it, but only because the chain around here offers it as ethanol free.
I buy most of my gas at Costco. They don’t offer midgrade gas.
I’d be more apt to say they don’t offer low grade gas as they have like 88/89 and 91/92 from the Costcos I’ve used. Never seen one with 87.
Odd as every Costco I’ve been to has 87 and 91 octane. I haven’t visited one in Nebraska though.
This was mainly MN ’13-’17. I just looked this up and appears it’s all 87/91 now for Costco from their page. I’ve never thought about Diesel from them as the MN/IA locations I visited didn’t have it, but that’s also an option. I’ll have to look at our Costco in DC for this now.
They do in California. Every Costco station has 87 and 91. Most every other non Costco station also offer 89 but I’m assuming this is just a mix of the two. There are stations that sell 100 but they are few and far between. I ran it a few times in my old ZX600R but it didn’t make a bit of difference.
E85 was a thing for a while but I haven’t seen it in years.
Costcos must vary by state as MN and IA locations I visited were 88/92 in ’13-17. Yes I’m now realizing that is a decade ago but it was a 1 octane up and lower price compared to the other stations offering 87/89/91
California also has its own blends of gas so that probably has something to do with it too.
There are a few E85 stations out here in SoCal, it’s just that there aren’t all that many of them. I know of one a few blocks from me and another about 15 miles away. If I was building some crazy forced-induction monster, I’d definitely run it.
87/93 in NC.
I’ll double check next visit to make sure the high option isn’t actually just 91. I’m just so used to buying premium I don’t fret over a 1 or 2 octane number difference.
The Costcos in the Denver area only offer 85 and 91 as “regular” and “premium”. Same for all other gas stations at altitude out here.
I put 89 in my 95 mustang. It shouldn’t need it but knocks on 87 bad, less so on 89, obviously a sign of problems but for now it helps
When she was younger and still did track work, my ’02 would get 89 to stop the occasional high rpm detonation I’d get.
And worse, 89 costs almost as much as 93!
The 93 premium will often be around $1 more than regular 87, with the midgrade 89 only being 10-20c less! LOL
You’re better off just using 87 regular and them adding an octane booster.
I’ve heard of people that run 89 in cars that call for 87 that have very high mileage. They’re concerned that carbon buildup can create “hot spots” on the pistons, risking pre-ignition on lower octane fuels. I’m not sure if that’s really a concern or not.
I’ve heard of people that run 89 in cars that call for 87 that that have very high mileage. They’re concerned that carbon buildup can create “hot spots” on the pistons, risking pre-ignition on lower octane fuels. I’m not sure if that’s really a concern or not.
My 87 chevy 3/4 ton with tbi 350 knocks like he’ll on 87. Eats oil worse than a 2 stroke. Gets 93 and is relatively happy. It’s a very tired engine and I’ve put the knocking down to hot spots/carbon build up on the heads. For the 5-600 miles a year it drives the few extra $ don’t bother me. And I’ve tried the sea foam hot soak to no effect
I’ve owned a couple of cars that ran a bit better on it so I used it for them. Early ’80s cars were sometimes less prone to run-on as well. I remember my stepmom’s ’70s Nova with a straight six wouldn’t stop running when you turned off the ignition, unless you pushed the gas peddle which would finally kill it, probably by flooding it. She always bought the cheapest gas she could find. I put octane booster in once just for fun and confusion. It didn’t run-on for a whole tank of gas.
I also believe some manufacturers would say their cars could handle the cheap stuff as a sales tactic when in fact their engines were happier with a little more octane.
Let me tell you about a product called unleaded 88. It goes in the middle slot and is actually cheaper than regular because it contains 15% ethanol. All new cars can take it without voiding the warranty. Coming from the midwest to a station near you.
This is more station brand dependent and I feel part of marketing and rounding up of octanes. One station offers 87/89/91 and another offers 88/90/93, but at a slightly higher price. Buyer’s will gravitate towards the higher number as perceived better even if it’s not necessary.
A lot of Midwestern stations offer 87 ethanol blend now (at least NE, IA, and MN). Crossing state lines and finding different octanes has always amused me. I remember see 85 and 86 in the South in the early ’90s and I had never seen that in the Midwest (87 always the lowest – pre ethanol era)
Unleaded 88 was originally a marketing campaign that I saw when watching Big 10 sports. Big corn wanted a brand name they could use for selling 15% ethanol in gas. Taking over the middle button on gas pumps was the goal.
The only station I have actually ever seen it at is Kwik Trip in Indiana. From their website:
“What is Unleaded 88?
Unleaded 88 is a blend of 84 octane gasoline and ethanol. The difference is Unleaded 87 has 10% ethanol and Unleaded 88 has 15% ethanol. The 5% increase in ethanol increases the octane rating to 88.”
So yes marketing. But also selling lower quality gasoline for a lower price, and then adding enough ethanol to make it run.
That sounds perfect for a DeLorean!
88 octane + 88 MPH= Time travel
I used to buy it for my Gen 1 Chevy Volt. GM specified Premium for it, but that was more about keeping ethanol out of the fuel to prolong it since the car drove mostly on electricity. It had a lower compression ratio than the second gen Volt that used regular gas.
So many Volt drivers suspect Premium isn’t actually necessary.
However, 87 caused a small amount of engine knock so I avoided it.
Mid grade, though? The car ran like a champ on it