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2021 Impreza Sport
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5 Posts
Interesting; the knock sensors should take care of that. If/when our Sport shows up, I'll have to give it a test. It should show up more in the summer heat here.
 

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407 Posts
Although the manual is asking for regular, I tried upgrading to plus. It could be in my head but the power behind it, and smoothness of the entire ride feels better.
OK, if you live at a high-altitude location where the gas is regularly 2 octane points lower, and then you drive down to low elevation, 'regular' COULD give you some pinging on the climb back up the mountain if you don't fill up with higher-octane low-elevation fuel.
 

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2020 Impreza Limited 5-door, Dark Blue with Ivory Leather.
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106 Posts
Interesting thread. Some good information here. Also some not so good information here. Just one point I would like to add... there are more differences than just octane ratings between Regular, Plus and Premium. There are also notable differences between gasoline brands.

It is true that the government requires that all gasoline sold for consumer use must contain a minimum level of detergents and other additives that help keep your fuel delivery system clean and reduce air pollution. So, let's assume that all gasolines sold in America meet those minimum standards. However, if you want your engine to perform well and last a long time, you need to use a gasoline brand that exceeds those minimum standards. Those are called the Top Tier gasoline marketers. The additives in the Top Tier brands far exceed the additive minimums. They cost a little more because they have more in them. If you don't believe me, check out this AAA report on gasoline from 2016...

70345370957240-14152908.pdf (trbas.com)

Peace... Mack
 

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Interesting thread. Some good information here. Also some not so good information here. Just one point I would like to add... there are more differences than just octane ratings between Regular, Plus and Premium. There are also notable differences between gasoline brands.

It is true that the government requires that all gasoline sold for consumer use must contain a minimum level of detergents and other additives that help keep your fuel delivery system clean and reduce air pollution. So, let's assume that all gasolines sold in America meet those minimum standards. However, if you want your engine to perform well and last a long time, you need to use a gasoline brand that exceeds those minimum standards. Those are called the Top Tier gasoline marketers. The additives in the Top Tier brands far exceed the additive minimums. They cost a little more because they have more in them. If you don't believe me, check out this AAA report on gasoline from 2016...

70345370957240-14152908.pdf (trbas.com)

Peace... Mack
While I believe that is true I was having problems with Costco gas which is top tier and most but not all have gone away switching to Shell. I was getting what I call surging or jerking, terrible mileage and just over all rough running. With Shell most went away but not completely. Mileage is better but not great and the surging is "mostly" gone. Once the engine is more broken in (I have a 2019 with only 8k miles) I'll try again to see if I notice a difference.
 

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2020 Impreza Limited 5-door, Dark Blue with Ivory Leather.
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106 Posts
While I believe that is true I was having problems with Costco gas which is top tier and most but not all have gone away switching to Shell. I was getting what I call surging or jerking, terrible mileage and just over all rough running. With Shell most went away but not completely. Mileage is better but not great and the surging is "mostly" gone. Once the engine is more broken in (I have a 2019 with only 8k miles) I'll try again to see if I notice a difference.
Hey Wheel... I have seen Costco on the Top Tier list, and often wondered if that was really true. They probably do sell good gas. Maybe you just had a bad tank or two. In any event, after 8,000 miles, I would say your engine is unquestionably broken in. However, with so few miles on a two-year-old car, could it be that your gas is going stale in the tank before you have a chance to use it? I use fuel stabilizer like Sta-Bil when I let any vehicle sit with gas in the tank for 60 days or more. Just something to consider.

Peace... Mack
 
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