5 ms·

Depends on what you call a specialty engine. Lots of these overall better engines are just highly improved fuel-injected V-8's. Quite run-of-the-mill today.

Depends on what you call a specialty engine. Lots of these overall better engines are just highly improved fuel-injected V-8's. Quite run-of-the-mill today. Never a specialty to me, when I was learning to drive the most common choices were between small-block V-8's and big-block V-8's. I think we can all be confident that serious resources did not go unwasted, especially after the returns made it to the shareholders of the oil companies.

elil17 4y ago
That's a specialty engine in new cars. In cars made today, you'd find that on a sports car. Older cars do often require higher octane gas because engine design was just worse back then. Less than 20% of new cars need high-octane fuel, and those that do are luxury/sports cars.
mrguyorama 4y ago
A modern V8 is absolutely fine with lower octane fuel. Massive improvements in fuel atomization, compression chamber shape, ignition timing, valve timing, air routing, cooling, basically literally everything about a combustion engine means that we can run a 5 litre V8 with an 11:1 compression ratio on 87 and make ungodly amounts of power. The reduction in required octane is directly related to the fact that old V8s that had garbage compression ratios and horrible fueling got muzzled by emissions regulations so they couldn't compensate for their mediocre engineering by just dumping extra fuel into the process. All those things listed above that are meant to improve resistance to knock ALSO bring way more efficiency, and the interesting thing about gas engines is that higher efficiency often means the specific output is boosted as well. Higher octane ONLY means a higher resistance to knocking. If your car isn't fighting knocking already, that won't improve anything. We could reduce the octane we require and get somewhat cheaper gas, but it would most likely also reduce the power output of the engine (fine nowadays) and the fuel economy (very not fine for most people).
- fuzzfactor 4y ago
  >A modern V8 is absolutely fine with lower octane fuel. True. I do it all the time. Even finer with higher octane fuel. I do that all the time too. Tell me which one allows you to accelerate better uphill with a loaded pickup truck.
  - elil17 4y ago
    Driving a truck up a hill is not a normal use case. Driving a luxury car is not normal. Driving a sports car is not normal. These are all specialty vehicles. Normal cars do not need high octane fuel. Normal cars do not benefit from high octane fuel. Car and Driver did a study of the effects of high octane fuel on a CRV, F-150, Charger, and BMW M5. Only the F-150 saw a >0.1s improvement to 0-60 time for high octane. High octane showed modest MPG improvements in some cases, but this were not enough to justify the higher costs. The CRV, the only remotely normal car in that study, actually had lower 0-60 performance on high octane fuel. https://www.caranddriver.com/features/a28565486/honda-cr-v-vs-bmw-m5-ford-f-150-dodge-charger/ https://www.caranddriver.com/features/a28565486/honda-cr-v-v... Americans waste $2.1 billion/year on high octane fuel they don't need. https://newsroom.aaa.com/2016/09/u-s-drivers-waste-2-1-billion-annually-premium-gasoline/ https://newsroom.aaa.com/2016/09/u-s-drivers-waste-2-1-billi... I'm not saying not to fill your truck up with high octane fuel. There is a reason to do that. But most people are obviously not driving that around to the grocery store or whatever - it's a specialty vehicle for your farm or work. There's no reason for anyone to fill up their normal, personal car with high octane fuel unless the manual says it's needed.
    - MichaelZuo 4y ago
      Normal cars and car drivers certainly drive up-hill.
      - elil17 4y ago
        And they don’t need high octane fuel to do so. It won’t change their acceleration.
        4y ago

elil17 4y ago

That's a specialty engine in new cars. In cars made today, you'd find that on a sports car. Older cars do often require higher octane gas because engine design was just worse back then. Less than 20% of new cars need high-octane fuel, and those that do are luxury/sports cars.

mrguyorama 4y ago

A modern V8 is absolutely fine with lower octane fuel. Massive improvements in fuel atomization, compression chamber shape, ignition timing, valve timing, air routing, cooling, basically literally everything about a combustion engine means that we can run a 5 litre V8 with an 11:1 compression ratio on 87 and make ungodly amounts of power. The reduction in required octane is directly related to the fact that old V8s that had garbage compression ratios and horrible fueling got muzzled by emissions regulations so they couldn't compensate for their mediocre engineering by just dumping extra fuel into the process. All those things listed above that are meant to improve resistance to knock ALSO bring way more efficiency, and the interesting thing about gas engines is that higher efficiency often means the specific output is boosted as well. Higher octane ONLY means a higher resistance to knocking. If your car isn't fighting knocking already, that won't improve anything. We could reduce the octane we require and get somewhat cheaper gas, but it would most likely also reduce the power output of the engine (fine nowadays) and the fuel economy (very not fine for most people).

fuzzfactor 4y ago
>A modern V8 is absolutely fine with lower octane fuel. True. I do it all the time. Even finer with higher octane fuel. I do that all the time too. Tell me which one allows you to accelerate better uphill with a loaded pickup truck.
- elil17 4y ago
  Driving a truck up a hill is not a normal use case. Driving a luxury car is not normal. Driving a sports car is not normal. These are all specialty vehicles. Normal cars do not need high octane fuel. Normal cars do not benefit from high octane fuel. Car and Driver did a study of the effects of high octane fuel on a CRV, F-150, Charger, and BMW M5. Only the F-150 saw a >0.1s improvement to 0-60 time for high octane. High octane showed modest MPG improvements in some cases, but this were not enough to justify the higher costs. The CRV, the only remotely normal car in that study, actually had lower 0-60 performance on high octane fuel. https://www.caranddriver.com/features/a28565486/honda-cr-v-vs-bmw-m5-ford-f-150-dodge-charger/ https://www.caranddriver.com/features/a28565486/honda-cr-v-v... Americans waste $2.1 billion/year on high octane fuel they don't need. https://newsroom.aaa.com/2016/09/u-s-drivers-waste-2-1-billion-annually-premium-gasoline/ https://newsroom.aaa.com/2016/09/u-s-drivers-waste-2-1-billi... I'm not saying not to fill your truck up with high octane fuel. There is a reason to do that. But most people are obviously not driving that around to the grocery store or whatever - it's a specialty vehicle for your farm or work. There's no reason for anyone to fill up their normal, personal car with high octane fuel unless the manual says it's needed.
  - MichaelZuo 4y ago
    Normal cars and car drivers certainly drive up-hill.
    - elil17 4y ago
      And they don’t need high octane fuel to do so. It won’t change their acceleration.
      - 4y ago