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
Years ago, my mother had bought a brand new santa fe, pretty much when they just came out for the first time, the ol carp on wheels.
Hers had the 2.7 and by god, it said 87 in the book, but got all pissy if you so used it, no matter where you got it, but if it had 89, it was a happy clam and soldered on like they always do delivering mediocre economy with a glass transmission.
We did try 93 since most here didnt bother with 91 and somehow it never made any difference in power, economy, or driveability, so it stayed at 89 so beats me as to why it was picky.
It’s a good place to do some math. I’ve tested this on my own vehicles, using pencil to paper not the lie panel. You need to run several tanks in a row of each for good averages. Record and average fuel economy using each fuel option, this is for vehicles not requiring high octane of course, then calculate the difference in average fuel economy versus the difference in price. In some vehicles the percentage in fuel economy gain offsets the percentage of cost increase between fuel grades. When fuel prices are lower the increase in price between grades is less and my Tahoe doesn’t cost any more per mile running premium than regular. Mid-grade is almost always a benefit for me over regular. When prices are high premium costs me more per mile. Also, you are correct in saying anything between regular and premium is a blend.
Back in the mid 00’s, my father was VP/GM at a larger drag strip that had a Sunoco gas pump that had unleaded 87, 94, 100, and a few actual leaded fuels up to i think 116 maybe. I dunno it’s been 20 years now. I had a pretty modded VW GTI 1.8T that put down about 300whp but the interesting bits were a GT28RS and a reasonably large aftermarket intercooler. Doesn’t sound like much now that factory + flash will get you that, but back then factory + flash got you maybe 200whp. Since I could free gas once in a while, I did some experiments one summer. full tank of 94, mix of 94/100, full tank of 100. I didn’t bother with 87 because even stock I could tell within 5 miles of driving if the car had 87 in it. That’s another story though*. Over the course of a month in the summer of 2004, the results were that the ol’ butt dyno could tell the difference between the 94 and the 94/100 mix, but not the 94/100 and full 100. Gas mileage was worse on 100 and 94. The sweet spot really was the 94/100 mix, so I suppose that’s about 97 octane. The ECU in those cars was very aggressive with timing as well as pulling it if it heard knock, which is probably why I could really tell the difference.
*Had a friend drop me off at the airport in 2003 in my own car so that I didn’t have to pay for parking with the caveat that he could drive it all week if he did so. I told him ‘Just don’t put shitty gas in it.’ He had been driving a mild mk3 GTI VR6, so jumping to a full bolt on 1.8T mk4 GTI was a pretty enticing upgrade. I get off the plane, get my bag and he pulls up. I hop in the drivers seat and before we’re even back on the highway, I looked at him and said ‘You put shitty gas in it, didn’t you?’ He was agog that I could tell, but you lost an estimate 10-15hp on 87 in that car. It was INSTANTLY noticeable if you’d had any amount of time driving it. That car was a factory freak though and ran 13.9’s off the show room floor when most others were mid 14’s.
This is a good subject since Nobody knows this for sure I’m just guessing.
My Stinger takes 91 Octane in order to not retard the Knock Sensor and get the so called Maximum power that the engine was designed to run with so its pushing 365bhp with 91.
But of course we can’t get anything less than 93 Octane around here and 93 costs about $4.40. So I’ve heard you shouldn’t keep changing the Octane for some reason so I fill with the 93 and when it gets to half full I refill with 89 for a mix of 91 in the end.
Bottom line is I wonder how important it is to do this but the car’s just got 12k miles and it’s a 2021 so it’s fairly new. I don’t race but I really push it hard sometimes and the MPG can drop to under 12mpg. Really costly compared to the 1970s lol! Hybrids weren’t that common when I bought this and the idea with a battery that I could get 30-40 highway would be terrific. City is horrible also at 17mpg.
Pay the piper for my fun.
Probably a perception that mid grade is better than regular, like people who insist on premium gas in a car that has need for it.
Having owned numerous Hemi engines over the years, I was one of the 7%.
Now, all my vehicles, even my 1977 K5 Blazer, require premium…
Yep, owned 2 Hemis and I ran 89 for most of the year in both.
In the dead of winter I’d run 87, because it *could* and I honestly never missed the response when it was under 30 degrees, and TBH I don’t think it knocked when the air intake temps were that cold.
I actually also ran 89 in my 3.5L V6 Chrysler 300M often as well. It’d return notably better throttle response, so it was worth it to me. I’d run 87 in winter or when I’d do a long road trip and burn through it.
I never really noticed ping or power loss with my 5.7s with 87, but when I tracked the fuel mileage I did notice a difference. Not enough to cover the difference in cost but enough it made me feel better that the 89 was the right choice
I have a brother in law with a Hemi Ram who runs 87 and says he gets the same mileage and power as he does with the 89, so your mileage may vary anyways.
Of course you don’t understand, you live in a country with a two party system.
We mostly have three grades here, 91, 95 and 98 (some places also sell an ethanol blend, e10, which is usually cheaper but apparently burns more quickly and can damage older cars). A lot of European cars specify 95 as the minimum octane and I suspect some performance cars might specify 98 – otherwise 91 is the most common. I have friends who use 98 in their bog-standard commutermobiles because they think it’s “better for the engine”, but I expect they’re in the minority.
I have to use 98 in my car as it’s a Japanese grey import that specifies “premium” fuel, which is 100 octane in Japan. 98 is close enough I suppose!
Europe and a lot of other places only use research octane numbers, the USA and Canada use an anti-knock index method which is the calculated average between the research octane and motor octane test scales so 98 RON is basically 91-93 AKI 91RON equivalent to 87 AKI, etc
Yeah I was aware of this, but couldn’t remember the terminology or the science behind it to explain it – so thank you for doing just that!
My main point was rather to show how the “middle one” is actually fairly popular here as it’s the minimum octane for a bunch of Euro cars.
My 2.5T boxer drops off mpg noticably with other than tier 1 premium.
This is because EJ engines are very sensitive to knocking/pinging/detonation (whatever you want to call it) and will pull/retard timing significantly when using lower octane fuel, which will result in lower fuel economy. Please put nice fuel in your turbo engine 🙂
The octane wasn’t a surprise, how much it needs the detergent specific to “tier 1” formulations was. I spent a year thinking it might have a secret thing for Chevron.
My base Saab CG900 takes 89.
Here in the UK we often only have the 2 to choose from, 95 and 98, Recently the 95 has been E10 where the 98 is E5. While the E10 is apparently bad for older cars I have run my T3 on it fine for years now, My Skyline gets the 98 though. I don’t recall ever seeing any intermediate grade here.
You don’t find it much anymore. I do remember that early 2300 Fords liked plus, they sounded like baby rattles on regular.
I don’t have any input, but I’m grateful to the examples and other commenters explaining, because this was also a question I’ve had for a while.
My 2.0T 9-3 says it needs 87 at minimum, but for best performance 90+. As I very rarely find 91 I just use 93 by default. I fill it up once a month at that so I don’t mind the cost increase
If I remember correctly the last time I got mid-grade was filling up my Mom’s 1996 Dodge Intrepid. The 3.5 V6 specified midgrade in the manual and at the fuel filler. I usually buy gas at Costco and they don’t carry midgrade at all, regular or premium only.
I used to drive Fords with various Ecoboost (turbo) engines. Although all of them could run on Regular, Premium was recommended to get the full power out of the motor, and the way I drove them made me feel like I should use Premium.
The only time I used Mid Grade is when I was broke but didn’t want to completely neglect the car.
One positive aspect of EV ownership? There’s only one grade of electricity. 😉
As a youth in Appalachia, I was told (as it was common knowledge) that the three grades were essentially ‘Good’, ‘Better’, ‘Best’. Somehow putting in higher octane would do good things for the engine, but these things were not clear. Most people have no idea what octane is and everything under the hood of the car, everything in their phone, everything in their tv, etc, could all be run by elves or black magic so long as it works. That leaves the door wide open for marketing to get people to buy things they don’t need, like ‘better’ gas. Now I get what my car requires and I know an ‘Octane rating’ is not the same as ‘percent octane’.
My ex had a ’15 X5 with the turbo’d six. She always bought premium (H-E-B 93 in TX). I tried one tank of 87 regular, and it was definitely less responsive but never knocked. The 89 “Mid Grade” seemed a decent compromise. During Hurricane Harvey, the local HEB ran out of regular and mid-grade but sold their remaining premium inventory for the price of regular to keep people moving for as long as they could and engender positive sentiment (or avoid being accused of price-gouging). It worked. People spoke positively about that decision for at least a couple of years afterwards.
Between the variability of our drives and the weather in SE TX, it was impossible to do any sort of mpg comparison.
The MDX that replaced the X5 ran fine on mid-grade despite the manual strongly suggesting premium. The ability for engines to adjust for different octane levels is a nice benefit of today’s engine management systems.
AFAIK, the ‘ability to adjust’ is a simple knock sensor, which will adjust the ignition timing when it detects engine knock. Thereby also reducing power (or responsiveness, as some put it). Knock sensors have been around for a long time (like decades), so it’s not something new. Of course, cheaper engines didn’t use them right away, but I would be surprised if there are still many car engines around without this technology.
I know that and don’t disagree. It’s just that the analog stuff I grew up driving didn’t have it.
N/A Honda’s are more peppy on higher octane gas, to the point where that may be the only difference with the higher HP Acura counterpart (premium recommended). 89 works if available, though we usually go with premium.
Yes the 05 MDX specifies mid-grade.
My 2017 V6 Accord runs fine on 87. The manual specs 87. And I doubt additional power (which is not needed) would show up if I went to a higher grade. The 2018 MDX recommends 91 octane, and the manual said it might occasionally ping on 87, but that it was acceptable. I compromised with 89.
Co-worker uses it for her F150 because the latest Coyote pick-ups apparently even need Premium, but she can’t really afford that. It made more sense to buy 89 (and I think 87 at times) and use octane booster “to make it 91”.
Otherwise, I imagine most people who buy 89 are Mopar owners with a 3.5, 5.7, or the HD 392. Even though that may be about 10 people, it’s what Chrysler recommends for those engines, despite 99% of owners seeing the “87 Octane Acceptable” note and run that instead.
Where I live, the price difference between 89 and 91 is so small that there’s hardly anything to be saved by running it. And if you assume a 50/50 mixture of 87 and 91, it’s not a good deal at all. May as well run 87 if you’re gonna be a cheapskate. I’ve owned only BMW’s for like the last 10 years so I just live at Costco and get 91 from there religiously.
I have a 2001 Olds Aurora 4.0. I put 93 in it. MUCH better power than on 87 or 89.
The Fleet Farm near me sells ethanol-free 89 (or so they say..) It’s popular with boaters in the area. I buy it because I don’t want ethanol in my mowers and I don’t need to spend the money on 91.
Nissan says the Juke (pauses for fruit and brickbats to die down) should run on at least 91 octane for best performance but can run on 89.
I buy 91 or 93 depending on how many gas discount points are on my Stop & Shop card.
I have a couple friends that deliver fuel for a chain around my location. I have been told that mid grade is a bit of a price rip off based on how the regular and premium is mixed to obtain it.
I pulled up an octane converter at http://www.wallaceracing.com/octane-chart.php to double check because I forgot what the formula was.
Around here, the octane ratings are 87/89/93. Using the calculator linked above, to make 89, the mix is 4 gallons of 87 and 2 gallons of 93.
Pricing per gallon is usually +$0.50 above 87 for midgrade and +$1.00 above 87 for premium.
If it were mixed 50/50 as the price indicates, mid grade would actually be 90.
I’ve seen some places that provide no ethanol options in the middle of the octane rating on their pumps. I started noticing when I had a classic car and wanted to avoid ethanol. While old cars, motorcycles, and other small engines that shouldn’t use ethanol might make up a small percentage of fuel consumption, I wonder if that contributes.